[v6,wave,2,1/3] hw/isa/lpc_ich9: add SMI feature negotiation via fw_cfg

Message ID 20170112182446.9600-2-lersek@redhat.com
State New
Headers show

Commit Message

Laszlo Ersek Jan. 12, 2017, 6:24 p.m.
Introduce the following fw_cfg files:

- "etc/smi/supported-features": a little endian uint64_t feature bitmap,
  presenting the features known by the host to the guest. Read-only for
  the guest.

  The content of this file will be determined via bit-granularity ICH9-LPC
  device properties, to be introduced later. For now, the bitmask is left
  zeroed. The bits will be set from machine type compat properties and on
  the QEMU command line, hence this file is not migrated.

- "etc/smi/requested-features": a little endian uint64_t feature bitmap,
  representing the features the guest would like to request. Read-write
  for the guest.

  The guest can freely (re)write this file, it has no direct consequence.
  Initial value is zero. A nonzero value causes the SMI-related fw_cfg
  files and fields that are under guest influence to be migrated.

- "etc/smi/features-ok": contains a uint8_t value, and it is read-only for
  the guest. When the guest selects the associated fw_cfg key, the guest
  features are validated against the host features. In case of error, the
  negotiation doesn't proceed, and the "features-ok" file remains zero. In
  case of success, the "features-ok" file becomes (uint8_t)1, and the
  negotiated features are locked down internally (to which no further
  changes are possible until reset).

  The initial value is zero.  A nonzero value causes the SMI-related
  fw_cfg files and fields that are under guest influence to be migrated.

The C-language fields backing the "supported-features" and
"requested-features" files are uint8_t arrays. This is because they carry
guest-side representation (our choice is little endian), while
VMSTATE_UINT64() assumes / implies host-side endianness for any uint64_t
fields. If we migrate a guest between hosts with different endiannesses
(which is possible with TCG), then the host-side value is preserved, and
the host-side representation is translated. This would be visible to the
guest through fw_cfg, unless we used plain byte arrays. So we do.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

---

Notes:
    v6:
    - no changes, pick up Michael's R-b
    
    v5:
    - rename the "etc/smi/host-features" fw_cfg file to
      "etc/smi/supported-features" [Igor]
    
    - rename the "etc/smi/guest-features" fw_cfg file to
      "etc/smi/requested-features" [Igor]
    
    - suffix the names of the "ICH9LPCState.smi_host_features" and
      "ICH9LPCState.smi_guest_features" array fields with "_le" for
      representing their guest-visible encoding [Igor]
    
    - Replace the "smi_host_features" parameter of ich9_lpc_pm_init() --
      which was meant in v4 to be set by  board code -- with a new
      "ICH9LPCState.smi_host_features" field, of type uint64_t.
      Bit-granularity ICH9-LPC device properties will be carved out of this
      field. [Igor]
    
    - Given the "ICH9LPCState.smi_host_features" uint64_t field, we can now
      use that directly for feature validation in
      smi_features_ok_callback(). Converting the (otherwise guest-read-only)
      "ICH9LPCState.smi_host_features_le" array back to CPU endianness just
      for this is no longer necessary.

 include/hw/i386/ich9.h | 10 +++++++
 hw/isa/lpc_ich9.c      | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 89 insertions(+)

-- 
2.9.3

Comments

Igor Mammedov Jan. 13, 2017, 10:15 a.m. | #1
On Thu, 12 Jan 2017 19:24:44 +0100
Laszlo Ersek <lersek@redhat.com> wrote:

> Introduce the following fw_cfg files:

> 

> - "etc/smi/supported-features": a little endian uint64_t feature bitmap,

>   presenting the features known by the host to the guest. Read-only for

>   the guest.

> 

>   The content of this file will be determined via bit-granularity ICH9-LPC

>   device properties, to be introduced later. For now, the bitmask is left

>   zeroed. The bits will be set from machine type compat properties and on

>   the QEMU command line, hence this file is not migrated.

> 

> - "etc/smi/requested-features": a little endian uint64_t feature bitmap,

>   representing the features the guest would like to request. Read-write

>   for the guest.

> 

>   The guest can freely (re)write this file, it has no direct consequence.

>   Initial value is zero. A nonzero value causes the SMI-related fw_cfg

>   files and fields that are under guest influence to be migrated.

> 

> - "etc/smi/features-ok": contains a uint8_t value, and it is read-only for

>   the guest. When the guest selects the associated fw_cfg key, the guest

>   features are validated against the host features. In case of error, the

>   negotiation doesn't proceed, and the "features-ok" file remains zero. In

>   case of success, the "features-ok" file becomes (uint8_t)1, and the

>   negotiated features are locked down internally (to which no further

>   changes are possible until reset).

> 

>   The initial value is zero.  A nonzero value causes the SMI-related

>   fw_cfg files and fields that are under guest influence to be migrated.

I'm still not quite sure if we need all this negotiation thingy with
all complexity it brings in when looking from cpu hotplug pov.

Paolo mentioned following security implications:
 1: OS could trigger broadcast SMI and try to hijack SMI handler for not
    yet relocated default SMI base of hotplugged CPU.
    That [c|sh]ould be handled by firmware protecting default SMI base.
 2: Even if firmware protected default SMI base, OS still could
    cause undefined behavior by sending broadcast SMI in case if more than
    1 CPU has been hotplugged, which would make unconfigured CPUs
    use the same SMI base simultaneously.
    Paolo suggested that real HW avoids the issue by making hotplugged CPUs
    "parked" until firmware unparks it from its SMI handler.
    So that's adds one more runtime state to migrate and qemu-guest ABI knob
    to maintain even if we ignore that there is no such terms as '(un)parked' in SDM.

How about considering an alternative simpler approach:
 * QEMU provides only "etc/smi/supported-features" file with SMI broadcast
   (no need to migrate)
 * firmware takes care of #1 by protecting default SMI base and using
   broadcast SMI if "etc/smi/supported-features" advertises it.
 * and QEMU could deal with #2 issue by just crashing guest as it tries
   to invoke undefined behavior (i.e. check that there is only 1 CPU with
   default SMI base and crash if there are more).
With this approach there is not need to negotiate nor migrate extra state
and inventing an unSPECed unpark knob for CPU hotplug could be avoided
(i.e. less qemu-guest ABI to maintain).


> 

> The C-language fields backing the "supported-features" and

> "requested-features" files are uint8_t arrays. This is because they carry

> guest-side representation (our choice is little endian), while

> VMSTATE_UINT64() assumes / implies host-side endianness for any uint64_t

> fields. If we migrate a guest between hosts with different endiannesses

> (which is possible with TCG), then the host-side value is preserved, and

> the host-side representation is translated. This would be visible to the

> guest through fw_cfg, unless we used plain byte arrays. So we do.

> 

> Cc: "Michael S. Tsirkin" <mst@redhat.com>

> Cc: Gerd Hoffmann <kraxel@redhat.com>

> Cc: Igor Mammedov <imammedo@redhat.com>

> Cc: Paolo Bonzini <pbonzini@redhat.com>

> Signed-off-by: Laszlo Ersek <lersek@redhat.com>

> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

> ---

> 

> Notes:

>     v6:

>     - no changes, pick up Michael's R-b

>     

>     v5:

>     - rename the "etc/smi/host-features" fw_cfg file to

>       "etc/smi/supported-features" [Igor]

>     

>     - rename the "etc/smi/guest-features" fw_cfg file to

>       "etc/smi/requested-features" [Igor]

>     

>     - suffix the names of the "ICH9LPCState.smi_host_features" and

>       "ICH9LPCState.smi_guest_features" array fields with "_le" for

>       representing their guest-visible encoding [Igor]

>     

>     - Replace the "smi_host_features" parameter of ich9_lpc_pm_init() --

>       which was meant in v4 to be set by  board code -- with a new

>       "ICH9LPCState.smi_host_features" field, of type uint64_t.

>       Bit-granularity ICH9-LPC device properties will be carved out of this

>       field. [Igor]

>     

>     - Given the "ICH9LPCState.smi_host_features" uint64_t field, we can now

>       use that directly for feature validation in

>       smi_features_ok_callback(). Converting the (otherwise guest-read-only)

>       "ICH9LPCState.smi_host_features_le" array back to CPU endianness just

>       for this is no longer necessary.

> 

>  include/hw/i386/ich9.h | 10 +++++++

>  hw/isa/lpc_ich9.c      | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++

>  2 files changed, 89 insertions(+)

> 

> diff --git a/include/hw/i386/ich9.h b/include/hw/i386/ich9.h

> index 5fd7e97d2347..da1118727146 100644

> --- a/include/hw/i386/ich9.h

> +++ b/include/hw/i386/ich9.h

> @@ -64,6 +64,16 @@ typedef struct ICH9LPCState {

>      uint8_t rst_cnt;

>      MemoryRegion rst_cnt_mem;

>  

> +    /* SMI feature negotiation via fw_cfg */

> +    uint64_t smi_host_features;       /* guest-invisible, host endian */

> +    uint8_t smi_host_features_le[8];  /* guest-visible, read-only, little

> +                                       * endian uint64_t */

> +    uint8_t smi_guest_features_le[8]; /* guest-visible, read-write, little

> +                                       * endian uint64_t */

> +    uint8_t smi_features_ok;          /* guest-visible, read-only; selecting it

> +                                       * triggers feature lockdown */

> +    uint64_t smi_negotiated_features; /* guest-invisible, host endian */

> +

>      /* isa bus */

>      ISABus *isa_bus;

>      MemoryRegion rcrb_mem; /* root complex register block */

> diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c

> index 10d1ee8b9310..376b7801a42c 100644

> --- a/hw/isa/lpc_ich9.c

> +++ b/hw/isa/lpc_ich9.c

> @@ -48,6 +48,8 @@

>  #include "exec/address-spaces.h"

>  #include "sysemu/sysemu.h"

>  #include "qom/cpu.h"

> +#include "hw/nvram/fw_cfg.h"

> +#include "qemu/cutils.h"

>  

>  /*****************************************************************************/

>  /* ICH9 LPC PCI to ISA bridge */

> @@ -360,13 +362,62 @@ static void ich9_set_sci(void *opaque, int irq_num, int level)

>      }

>  }

>  

> +static void smi_features_ok_callback(void *opaque)

> +{

> +    ICH9LPCState *lpc = opaque;

> +    uint64_t guest_features;

> +

> +    if (lpc->smi_features_ok) {

> +        /* negotiation already complete, features locked */

> +        return;

> +    }

> +

> +    memcpy(&guest_features, lpc->smi_guest_features_le, sizeof guest_features);

> +    le64_to_cpus(&guest_features);

> +    if (guest_features & ~lpc->smi_host_features) {

> +        /* guest requests invalid features, leave @features_ok at zero */

> +        return;

> +    }

> +

> +    /* valid feature subset requested, lock it down, report success */

> +    lpc->smi_negotiated_features = guest_features;

> +    lpc->smi_features_ok = 1;

> +}

> +

>  void ich9_lpc_pm_init(PCIDevice *lpc_pci, bool smm_enabled)

>  {

>      ICH9LPCState *lpc = ICH9_LPC_DEVICE(lpc_pci);

>      qemu_irq sci_irq;

> +    FWCfgState *fw_cfg = fw_cfg_find();

>  

>      sci_irq = qemu_allocate_irq(ich9_set_sci, lpc, 0);

>      ich9_pm_init(lpc_pci, &lpc->pm, smm_enabled, sci_irq);

> +

> +    if (lpc->smi_host_features && fw_cfg) {

> +        uint64_t host_features_le;

> +

> +        host_features_le = cpu_to_le64(lpc->smi_host_features);

> +        memcpy(lpc->smi_host_features_le, &host_features_le,

> +               sizeof host_features_le);

> +        fw_cfg_add_file(fw_cfg, "etc/smi/supported-features",

> +                        lpc->smi_host_features_le,

> +                        sizeof lpc->smi_host_features_le);

> +

> +        /* The other two guest-visible fields are cleared on device reset, we

> +         * just link them into fw_cfg here.

> +         */

> +        fw_cfg_add_file_callback(fw_cfg, "etc/smi/requested-features",

> +                                 NULL, NULL,

> +                                 lpc->smi_guest_features_le,

> +                                 sizeof lpc->smi_guest_features_le,

> +                                 false);

> +        fw_cfg_add_file_callback(fw_cfg, "etc/smi/features-ok",

> +                                 smi_features_ok_callback, lpc,

> +                                 &lpc->smi_features_ok,

> +                                 sizeof lpc->smi_features_ok,

> +                                 true);

> +    }

> +

>      ich9_lpc_reset(&lpc->d.qdev);

>  }

>  

> @@ -507,6 +558,10 @@ static void ich9_lpc_reset(DeviceState *qdev)

>  

>      lpc->sci_level = 0;

>      lpc->rst_cnt = 0;

> +

> +    memset(lpc->smi_guest_features_le, 0, sizeof lpc->smi_guest_features_le);

> +    lpc->smi_features_ok = 0;

> +    lpc->smi_negotiated_features = 0;

>  }

>  

>  /* root complex register block is mapped into memory space */

> @@ -668,6 +723,29 @@ static const VMStateDescription vmstate_ich9_rst_cnt = {

>      }

>  };

>  

> +static bool ich9_smi_feat_needed(void *opaque)

> +{

> +    ICH9LPCState *lpc = opaque;

> +

> +    return !buffer_is_zero(lpc->smi_guest_features_le,

> +                           sizeof lpc->smi_guest_features_le) ||

> +           lpc->smi_features_ok;

> +}

> +

> +static const VMStateDescription vmstate_ich9_smi_feat = {

> +    .name = "ICH9LPC/smi_feat",

> +    .version_id = 1,

> +    .minimum_version_id = 1,

> +    .needed = ich9_smi_feat_needed,

> +    .fields = (VMStateField[]) {

> +        VMSTATE_UINT8_ARRAY(smi_guest_features_le, ICH9LPCState,

> +                            sizeof(uint64_t)),

> +        VMSTATE_UINT8(smi_features_ok, ICH9LPCState),

> +        VMSTATE_UINT64(smi_negotiated_features, ICH9LPCState),

> +        VMSTATE_END_OF_LIST()

> +    }

> +};

> +

>  static const VMStateDescription vmstate_ich9_lpc = {

>      .name = "ICH9LPC",

>      .version_id = 1,

> @@ -683,6 +761,7 @@ static const VMStateDescription vmstate_ich9_lpc = {

>      },

>      .subsections = (const VMStateDescription*[]) {

>          &vmstate_ich9_rst_cnt,

> +        &vmstate_ich9_smi_feat,

>          NULL

>      }

>  };
Laszlo Ersek Jan. 13, 2017, 11:24 a.m. | #2
On 01/13/17 11:15, Igor Mammedov wrote:
> On Thu, 12 Jan 2017 19:24:44 +0100

> Laszlo Ersek <lersek@redhat.com> wrote:

> 

>> Introduce the following fw_cfg files:

>>

>> - "etc/smi/supported-features": a little endian uint64_t feature bitmap,

>>   presenting the features known by the host to the guest. Read-only for

>>   the guest.

>>

>>   The content of this file will be determined via bit-granularity ICH9-LPC

>>   device properties, to be introduced later. For now, the bitmask is left

>>   zeroed. The bits will be set from machine type compat properties and on

>>   the QEMU command line, hence this file is not migrated.

>>

>> - "etc/smi/requested-features": a little endian uint64_t feature bitmap,

>>   representing the features the guest would like to request. Read-write

>>   for the guest.

>>

>>   The guest can freely (re)write this file, it has no direct consequence.

>>   Initial value is zero. A nonzero value causes the SMI-related fw_cfg

>>   files and fields that are under guest influence to be migrated.

>>

>> - "etc/smi/features-ok": contains a uint8_t value, and it is read-only for

>>   the guest. When the guest selects the associated fw_cfg key, the guest

>>   features are validated against the host features. In case of error, the

>>   negotiation doesn't proceed, and the "features-ok" file remains zero. In

>>   case of success, the "features-ok" file becomes (uint8_t)1, and the

>>   negotiated features are locked down internally (to which no further

>>   changes are possible until reset).

>>

>>   The initial value is zero.  A nonzero value causes the SMI-related

>>   fw_cfg files and fields that are under guest influence to be migrated.

> I'm still not quite sure if we need all this negotiation thingy with

> all complexity it brings in when looking from cpu hotplug pov.


It's not VCPU hotplug that necessitates feature negotiation at this
point. The broadcast SMI feature is more foundational than VCPU hotplug.
Broadcast SMI is necessary for *generally* improving correctness and
performance of the edk2 SMM stack, as built into OVMF and run on QEMU,
with VCPU hotplug not even in the picture.

Summarizing the feedback from Paolo, Michael and Kevin O'Connor, the
guidance was clearly that
- we needed feature negotiation,
- it should resemble virtio,
- it should not be some ad-hoc IO port hackery, but a reusable method
  for future firmware stuff that needs negotiation.

> 

> Paolo mentioned following security implications:


Frankly, for the scope of this work, I absolutely don't care about VCPU
hotplug specifically. VCPU hotplug is a feature that will certainly
depend on the robustness and reliability of the edk2 SMM stack, as it is
currently available for use in OVMF. These patches improve that
robustness and reliability.

The only consideration for VCPU hotplug at the moment is that, should it
need some negotiable features, the fw_cfg pattern should be able to
accommodate them. That's all.

Discussing any VCPU hotplug specifics at the moment has no merit, in my
opinion. I have not seen, or run, a single line of edk2 SMM code related
to VCPU hotplug. Whatever theories we make up will hang in the air.
Meanwhile the basic SMM stack doesn't work reliably -- it needs these
patches.

>  1: OS could trigger broadcast SMI and try to hijack SMI handler for not

>     yet relocated default SMI base of hotplugged CPU.

>     That [c|sh]ould be handled by firmware protecting default SMI base.

>  2: Even if firmware protected default SMI base, OS still could

>     cause undefined behavior by sending broadcast SMI in case if more than

>     1 CPU has been hotplugged, which would make unconfigured CPUs

>     use the same SMI base simultaneously.

>     Paolo suggested that real HW avoids the issue by making hotplugged CPUs

>     "parked" until firmware unparks it from its SMI handler.

>     So that's adds one more runtime state to migrate and qemu-guest ABI knob

>     to maintain even if we ignore that there is no such terms as '(un)parked' in SDM.

> 

> How about considering an alternative simpler approach:

>  * QEMU provides only "etc/smi/supported-features" file with SMI broadcast

>    (no need to migrate)

>  * firmware takes care of #1 by protecting default SMI base and using

>    broadcast SMI if "etc/smi/supported-features" advertises it.

>  * and QEMU could deal with #2 issue by just crashing guest as it tries

>    to invoke undefined behavior (i.e. check that there is only 1 CPU with

>    default SMI base and crash if there are more).

> With this approach there is not need to negotiate nor migrate extra state

> and inventing an unSPECed unpark knob for CPU hotplug could be avoided

> (i.e. less qemu-guest ABI to maintain).


The virtio-like feature negotiation (with host-features, guest-features,
and features-ok) has been part of the design since v3
<http://lists.nongnu.org/archive/html/qemu-devel/2016-11/msg03582.html>.

I'm confused why you are raising such concerns now, for v6, when the
v4->v5 iteration was done mainly to address your -- much welcomed! --
feedback. At that point, you seemed to agree with the general design,
and suggested implementation-level improvements, and I was happy to oblige.

The current protocol can accommodate simpler uses; a simpler protocol
might be less future-proof. Virtio, which is the pattern that the
current fw_cfg design follows, is historically proven, and the resultant
fw_cfg code complexity and migration footprint are not high.

Also, when you say "firmware takes care of #1 by protecting default SMI
base", you might be unknowingly suggesting changes for the SMM core
drivers in edk2 that are simply impossible for me to implement (or even
design).

I wish all people finally understood that UEFI / edk2 is not SeaBIOS,
where you just dig down and do whatever's necessary, in whatever way
that you see fit. edk2 is the reference implementation of the PI and
UEFI specs, which are themselves developed by *closed* standards-bodies.
(The specs are released publicly, but the spec development process is
proprietary.)

The specs facilitate interoperability between *binary* modules,
specifying, and thereby ossifying, low-level, internal interfaces
between components. This is the *polar opposite* of what most people are
used to in open source development (notably, Linux, but SeaBIOS too),
where internal interfaces are subject to continuous change and
improvement. (See "Documentation/stable_api_nonsense.txt".)

In brief, the PI and UEFI specs can be called "standardized cruft" that
exist in order to ensure interop between proprietary vendors.

I have reasonable freedom in modifying platfrom code (which lives under
OvmfPkg), and minimal freedom for core code -- e.g.
UefiCpuPkg/PiSmmCpuDxeSmm (the most critical SMM driver).

Specifically, the OVMF-side code -- which I've written and tested, but
not posted yet -- that will interface with this QEMU feature, lives
entirely in OvmfPkg. That's why this approach is possible at all.

And it is enabled only by the fact that the PI spec delegates the
EFI_SMM_CONTROL2_PROTOCOL.Trigger() method to individual platforms.
That's why I can have a say in the circumstances of SMI injection.

SMBASE handling is entirely out of the platform's hands. I estimate that
my SMM- and multiprocessing-related patches in edk2 (mainly OvmfPkg, but
also some bugfixes in more core modules) could be approaching the eighty
or hundred count, and I haven't once dealt directly with SMBASE
relocation or protection in that time.

Thus, please let's not change the design at this point.

Thanks
Laszlo

> 

> 

>>

>> The C-language fields backing the "supported-features" and

>> "requested-features" files are uint8_t arrays. This is because they carry

>> guest-side representation (our choice is little endian), while

>> VMSTATE_UINT64() assumes / implies host-side endianness for any uint64_t

>> fields. If we migrate a guest between hosts with different endiannesses

>> (which is possible with TCG), then the host-side value is preserved, and

>> the host-side representation is translated. This would be visible to the

>> guest through fw_cfg, unless we used plain byte arrays. So we do.

>>

>> Cc: "Michael S. Tsirkin" <mst@redhat.com>

>> Cc: Gerd Hoffmann <kraxel@redhat.com>

>> Cc: Igor Mammedov <imammedo@redhat.com>

>> Cc: Paolo Bonzini <pbonzini@redhat.com>

>> Signed-off-by: Laszlo Ersek <lersek@redhat.com>

>> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

>> ---

>>

>> Notes:

>>     v6:

>>     - no changes, pick up Michael's R-b

>>     

>>     v5:

>>     - rename the "etc/smi/host-features" fw_cfg file to

>>       "etc/smi/supported-features" [Igor]

>>     

>>     - rename the "etc/smi/guest-features" fw_cfg file to

>>       "etc/smi/requested-features" [Igor]

>>     

>>     - suffix the names of the "ICH9LPCState.smi_host_features" and

>>       "ICH9LPCState.smi_guest_features" array fields with "_le" for

>>       representing their guest-visible encoding [Igor]

>>     

>>     - Replace the "smi_host_features" parameter of ich9_lpc_pm_init() --

>>       which was meant in v4 to be set by  board code -- with a new

>>       "ICH9LPCState.smi_host_features" field, of type uint64_t.

>>       Bit-granularity ICH9-LPC device properties will be carved out of this

>>       field. [Igor]

>>     

>>     - Given the "ICH9LPCState.smi_host_features" uint64_t field, we can now

>>       use that directly for feature validation in

>>       smi_features_ok_callback(). Converting the (otherwise guest-read-only)

>>       "ICH9LPCState.smi_host_features_le" array back to CPU endianness just

>>       for this is no longer necessary.

>>

>>  include/hw/i386/ich9.h | 10 +++++++

>>  hw/isa/lpc_ich9.c      | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++

>>  2 files changed, 89 insertions(+)

>>

>> diff --git a/include/hw/i386/ich9.h b/include/hw/i386/ich9.h

>> index 5fd7e97d2347..da1118727146 100644

>> --- a/include/hw/i386/ich9.h

>> +++ b/include/hw/i386/ich9.h

>> @@ -64,6 +64,16 @@ typedef struct ICH9LPCState {

>>      uint8_t rst_cnt;

>>      MemoryRegion rst_cnt_mem;

>>  

>> +    /* SMI feature negotiation via fw_cfg */

>> +    uint64_t smi_host_features;       /* guest-invisible, host endian */

>> +    uint8_t smi_host_features_le[8];  /* guest-visible, read-only, little

>> +                                       * endian uint64_t */

>> +    uint8_t smi_guest_features_le[8]; /* guest-visible, read-write, little

>> +                                       * endian uint64_t */

>> +    uint8_t smi_features_ok;          /* guest-visible, read-only; selecting it

>> +                                       * triggers feature lockdown */

>> +    uint64_t smi_negotiated_features; /* guest-invisible, host endian */

>> +

>>      /* isa bus */

>>      ISABus *isa_bus;

>>      MemoryRegion rcrb_mem; /* root complex register block */

>> diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c

>> index 10d1ee8b9310..376b7801a42c 100644

>> --- a/hw/isa/lpc_ich9.c

>> +++ b/hw/isa/lpc_ich9.c

>> @@ -48,6 +48,8 @@

>>  #include "exec/address-spaces.h"

>>  #include "sysemu/sysemu.h"

>>  #include "qom/cpu.h"

>> +#include "hw/nvram/fw_cfg.h"

>> +#include "qemu/cutils.h"

>>  

>>  /*****************************************************************************/

>>  /* ICH9 LPC PCI to ISA bridge */

>> @@ -360,13 +362,62 @@ static void ich9_set_sci(void *opaque, int irq_num, int level)

>>      }

>>  }

>>  

>> +static void smi_features_ok_callback(void *opaque)

>> +{

>> +    ICH9LPCState *lpc = opaque;

>> +    uint64_t guest_features;

>> +

>> +    if (lpc->smi_features_ok) {

>> +        /* negotiation already complete, features locked */

>> +        return;

>> +    }

>> +

>> +    memcpy(&guest_features, lpc->smi_guest_features_le, sizeof guest_features);

>> +    le64_to_cpus(&guest_features);

>> +    if (guest_features & ~lpc->smi_host_features) {

>> +        /* guest requests invalid features, leave @features_ok at zero */

>> +        return;

>> +    }

>> +

>> +    /* valid feature subset requested, lock it down, report success */

>> +    lpc->smi_negotiated_features = guest_features;

>> +    lpc->smi_features_ok = 1;

>> +}

>> +

>>  void ich9_lpc_pm_init(PCIDevice *lpc_pci, bool smm_enabled)

>>  {

>>      ICH9LPCState *lpc = ICH9_LPC_DEVICE(lpc_pci);

>>      qemu_irq sci_irq;

>> +    FWCfgState *fw_cfg = fw_cfg_find();

>>  

>>      sci_irq = qemu_allocate_irq(ich9_set_sci, lpc, 0);

>>      ich9_pm_init(lpc_pci, &lpc->pm, smm_enabled, sci_irq);

>> +

>> +    if (lpc->smi_host_features && fw_cfg) {

>> +        uint64_t host_features_le;

>> +

>> +        host_features_le = cpu_to_le64(lpc->smi_host_features);

>> +        memcpy(lpc->smi_host_features_le, &host_features_le,

>> +               sizeof host_features_le);

>> +        fw_cfg_add_file(fw_cfg, "etc/smi/supported-features",

>> +                        lpc->smi_host_features_le,

>> +                        sizeof lpc->smi_host_features_le);

>> +

>> +        /* The other two guest-visible fields are cleared on device reset, we

>> +         * just link them into fw_cfg here.

>> +         */

>> +        fw_cfg_add_file_callback(fw_cfg, "etc/smi/requested-features",

>> +                                 NULL, NULL,

>> +                                 lpc->smi_guest_features_le,

>> +                                 sizeof lpc->smi_guest_features_le,

>> +                                 false);

>> +        fw_cfg_add_file_callback(fw_cfg, "etc/smi/features-ok",

>> +                                 smi_features_ok_callback, lpc,

>> +                                 &lpc->smi_features_ok,

>> +                                 sizeof lpc->smi_features_ok,

>> +                                 true);

>> +    }

>> +

>>      ich9_lpc_reset(&lpc->d.qdev);

>>  }

>>  

>> @@ -507,6 +558,10 @@ static void ich9_lpc_reset(DeviceState *qdev)

>>  

>>      lpc->sci_level = 0;

>>      lpc->rst_cnt = 0;

>> +

>> +    memset(lpc->smi_guest_features_le, 0, sizeof lpc->smi_guest_features_le);

>> +    lpc->smi_features_ok = 0;

>> +    lpc->smi_negotiated_features = 0;

>>  }

>>  

>>  /* root complex register block is mapped into memory space */

>> @@ -668,6 +723,29 @@ static const VMStateDescription vmstate_ich9_rst_cnt = {

>>      }

>>  };

>>  

>> +static bool ich9_smi_feat_needed(void *opaque)

>> +{

>> +    ICH9LPCState *lpc = opaque;

>> +

>> +    return !buffer_is_zero(lpc->smi_guest_features_le,

>> +                           sizeof lpc->smi_guest_features_le) ||

>> +           lpc->smi_features_ok;

>> +}

>> +

>> +static const VMStateDescription vmstate_ich9_smi_feat = {

>> +    .name = "ICH9LPC/smi_feat",

>> +    .version_id = 1,

>> +    .minimum_version_id = 1,

>> +    .needed = ich9_smi_feat_needed,

>> +    .fields = (VMStateField[]) {

>> +        VMSTATE_UINT8_ARRAY(smi_guest_features_le, ICH9LPCState,

>> +                            sizeof(uint64_t)),

>> +        VMSTATE_UINT8(smi_features_ok, ICH9LPCState),

>> +        VMSTATE_UINT64(smi_negotiated_features, ICH9LPCState),

>> +        VMSTATE_END_OF_LIST()

>> +    }

>> +};

>> +

>>  static const VMStateDescription vmstate_ich9_lpc = {

>>      .name = "ICH9LPC",

>>      .version_id = 1,

>> @@ -683,6 +761,7 @@ static const VMStateDescription vmstate_ich9_lpc = {

>>      },

>>      .subsections = (const VMStateDescription*[]) {

>>          &vmstate_ich9_rst_cnt,

>> +        &vmstate_ich9_smi_feat,

>>          NULL

>>      }

>>  };

>
Igor Mammedov Jan. 13, 2017, 1:34 p.m. | #3
On Thu, 12 Jan 2017 19:24:44 +0100
Laszlo Ersek <lersek@redhat.com> wrote:

[...]
> +static void smi_features_ok_callback(void *opaque)

> +{

> +    ICH9LPCState *lpc = opaque;

> +    uint64_t guest_features;

> +

> +    if (lpc->smi_features_ok) {

> +        /* negotiation already complete, features locked */

> +        return;

> +    }

> +

> +    memcpy(&guest_features, lpc->smi_guest_features_le, sizeof guest_features);

> +    le64_to_cpus(&guest_features);

> +    if (guest_features & ~lpc->smi_host_features) {

> +        /* guest requests invalid features, leave @features_ok at zero */

> +        return;

> +    }

> +

> +    /* valid feature subset requested, lock it down, report success */

> +    lpc->smi_negotiated_features = guest_features;

> +    lpc->smi_features_ok = 1;

> +}

[...]

> +    .fields = (VMStateField[]) {

> +        VMSTATE_UINT8_ARRAY(smi_guest_features_le, ICH9LPCState,

> +                            sizeof(uint64_t)),

> +        VMSTATE_UINT8(smi_features_ok, ICH9LPCState),

> +        VMSTATE_UINT64(smi_negotiated_features, ICH9LPCState),


Couldn't smi_negotiated_features be derived from
smi_guest_features_le on target side?


> +        VMSTATE_END_OF_LIST()

> +    }

> +};

> +

>  static const VMStateDescription vmstate_ich9_lpc = {

>      .name = "ICH9LPC",

>      .version_id = 1,

> @@ -683,6 +761,7 @@ static const VMStateDescription vmstate_ich9_lpc = {

>      },

>      .subsections = (const VMStateDescription*[]) {

>          &vmstate_ich9_rst_cnt,

> +        &vmstate_ich9_smi_feat,

>          NULL

>      }

>  };
Laszlo Ersek Jan. 16, 2017, 8:51 p.m. | #4
On 01/13/17 14:34, Igor Mammedov wrote:
> On Thu, 12 Jan 2017 19:24:44 +0100

> Laszlo Ersek <lersek@redhat.com> wrote:

> 

> [...]

>> +static void smi_features_ok_callback(void *opaque)

>> +{

>> +    ICH9LPCState *lpc = opaque;

>> +    uint64_t guest_features;

>> +

>> +    if (lpc->smi_features_ok) {

>> +        /* negotiation already complete, features locked */

>> +        return;

>> +    }

>> +

>> +    memcpy(&guest_features, lpc->smi_guest_features_le, sizeof guest_features);

>> +    le64_to_cpus(&guest_features);

>> +    if (guest_features & ~lpc->smi_host_features) {

>> +        /* guest requests invalid features, leave @features_ok at zero */

>> +        return;

>> +    }

>> +

>> +    /* valid feature subset requested, lock it down, report success */

>> +    lpc->smi_negotiated_features = guest_features;

>> +    lpc->smi_features_ok = 1;

>> +}

> [...]

> 

>> +    .fields = (VMStateField[]) {

>> +        VMSTATE_UINT8_ARRAY(smi_guest_features_le, ICH9LPCState,

>> +                            sizeof(uint64_t)),

>> +        VMSTATE_UINT8(smi_features_ok, ICH9LPCState),

>> +        VMSTATE_UINT64(smi_negotiated_features, ICH9LPCState),

> 

> Couldn't smi_negotiated_features be derived from

> smi_guest_features_le on target side?


No, that's something we must expressly not do.

The "guest-features" file remains writeable (and back-readable) to the
guest after feature validation/lockdown (i.e., after selecting
"features-ok"), it just has no effect on QEMU.

And, if the guest rewrites "guest-features" between feature lockdown and
migration, that must have no effect on the target host either. Hence we
must carry forward the negotiated features originally computed on the
source host.

Thanks
Laszlo

> 

> 

>> +        VMSTATE_END_OF_LIST()

>> +    }

>> +};

>> +

>>  static const VMStateDescription vmstate_ich9_lpc = {

>>      .name = "ICH9LPC",

>>      .version_id = 1,

>> @@ -683,6 +761,7 @@ static const VMStateDescription vmstate_ich9_lpc = {

>>      },

>>      .subsections = (const VMStateDescription*[]) {

>>          &vmstate_ich9_rst_cnt,

>> +        &vmstate_ich9_smi_feat,

>>          NULL

>>      }

>>  };

>
Igor Mammedov Jan. 17, 2017, 8:42 a.m. | #5
On Mon, 16 Jan 2017 21:51:34 +0100
Laszlo Ersek <lersek@redhat.com> wrote:

> On 01/13/17 14:34, Igor Mammedov wrote:

> > On Thu, 12 Jan 2017 19:24:44 +0100

> > Laszlo Ersek <lersek@redhat.com> wrote:

> > 

> > [...]  

> >> +static void smi_features_ok_callback(void *opaque)

> >> +{

> >> +    ICH9LPCState *lpc = opaque;

> >> +    uint64_t guest_features;

> >> +

> >> +    if (lpc->smi_features_ok) {

> >> +        /* negotiation already complete, features locked */

> >> +        return;

> >> +    }

> >> +

> >> +    memcpy(&guest_features, lpc->smi_guest_features_le, sizeof guest_features);

> >> +    le64_to_cpus(&guest_features);

> >> +    if (guest_features & ~lpc->smi_host_features) {

> >> +        /* guest requests invalid features, leave @features_ok at zero */

> >> +        return;

> >> +    }

> >> +

> >> +    /* valid feature subset requested, lock it down, report success */

> >> +    lpc->smi_negotiated_features = guest_features;

> >> +    lpc->smi_features_ok = 1;

> >> +}  

> > [...]

> >   

> >> +    .fields = (VMStateField[]) {

> >> +        VMSTATE_UINT8_ARRAY(smi_guest_features_le, ICH9LPCState,

> >> +                            sizeof(uint64_t)),

> >> +        VMSTATE_UINT8(smi_features_ok, ICH9LPCState),

> >> +        VMSTATE_UINT64(smi_negotiated_features, ICH9LPCState),  

> > 

> > Couldn't smi_negotiated_features be derived from

> > smi_guest_features_le on target side?  

> 

> No, that's something we must expressly not do.

> 

> The "guest-features" file remains writeable (and back-readable) to the

> guest after feature validation/lockdown (i.e., after selecting

> "features-ok"), it just has no effect on QEMU.

> 

> And, if the guest rewrites "guest-features" between feature lockdown and

> migration, that must have no effect on the target host either. Hence we

> must carry forward the negotiated features originally computed on the

> source host.

ok,
patch looks good to me, so

Reviewed-by: Igor Mammedov <imammedo@redhat.com>


> Thanks

> Laszlo

> 

> > 

> >   

> >> +        VMSTATE_END_OF_LIST()

> >> +    }

> >> +};

> >> +

> >>  static const VMStateDescription vmstate_ich9_lpc = {

> >>      .name = "ICH9LPC",

> >>      .version_id = 1,

> >> @@ -683,6 +761,7 @@ static const VMStateDescription vmstate_ich9_lpc = {

> >>      },

> >>      .subsections = (const VMStateDescription*[]) {

> >>          &vmstate_ich9_rst_cnt,

> >> +        &vmstate_ich9_smi_feat,

> >>          NULL

> >>      }

> >>  };  

> >   

> 

>

Patch hide | download patch | download mbox

diff --git a/include/hw/i386/ich9.h b/include/hw/i386/ich9.h
index 5fd7e97d2347..da1118727146 100644
--- a/include/hw/i386/ich9.h
+++ b/include/hw/i386/ich9.h
@@ -64,6 +64,16 @@  typedef struct ICH9LPCState {
     uint8_t rst_cnt;
     MemoryRegion rst_cnt_mem;
 
+    /* SMI feature negotiation via fw_cfg */
+    uint64_t smi_host_features;       /* guest-invisible, host endian */
+    uint8_t smi_host_features_le[8];  /* guest-visible, read-only, little
+                                       * endian uint64_t */
+    uint8_t smi_guest_features_le[8]; /* guest-visible, read-write, little
+                                       * endian uint64_t */
+    uint8_t smi_features_ok;          /* guest-visible, read-only; selecting it
+                                       * triggers feature lockdown */
+    uint64_t smi_negotiated_features; /* guest-invisible, host endian */
+
     /* isa bus */
     ISABus *isa_bus;
     MemoryRegion rcrb_mem; /* root complex register block */
diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c
index 10d1ee8b9310..376b7801a42c 100644
--- a/hw/isa/lpc_ich9.c
+++ b/hw/isa/lpc_ich9.c
@@ -48,6 +48,8 @@ 
 #include "exec/address-spaces.h"
 #include "sysemu/sysemu.h"
 #include "qom/cpu.h"
+#include "hw/nvram/fw_cfg.h"
+#include "qemu/cutils.h"
 
 /*****************************************************************************/
 /* ICH9 LPC PCI to ISA bridge */
@@ -360,13 +362,62 @@  static void ich9_set_sci(void *opaque, int irq_num, int level)
     }
 }
 
+static void smi_features_ok_callback(void *opaque)
+{
+    ICH9LPCState *lpc = opaque;
+    uint64_t guest_features;
+
+    if (lpc->smi_features_ok) {
+        /* negotiation already complete, features locked */
+        return;
+    }
+
+    memcpy(&guest_features, lpc->smi_guest_features_le, sizeof guest_features);
+    le64_to_cpus(&guest_features);
+    if (guest_features & ~lpc->smi_host_features) {
+        /* guest requests invalid features, leave @features_ok at zero */
+        return;
+    }
+
+    /* valid feature subset requested, lock it down, report success */
+    lpc->smi_negotiated_features = guest_features;
+    lpc->smi_features_ok = 1;
+}
+
 void ich9_lpc_pm_init(PCIDevice *lpc_pci, bool smm_enabled)
 {
     ICH9LPCState *lpc = ICH9_LPC_DEVICE(lpc_pci);
     qemu_irq sci_irq;
+    FWCfgState *fw_cfg = fw_cfg_find();
 
     sci_irq = qemu_allocate_irq(ich9_set_sci, lpc, 0);
     ich9_pm_init(lpc_pci, &lpc->pm, smm_enabled, sci_irq);
+
+    if (lpc->smi_host_features && fw_cfg) {
+        uint64_t host_features_le;
+
+        host_features_le = cpu_to_le64(lpc->smi_host_features);
+        memcpy(lpc->smi_host_features_le, &host_features_le,
+               sizeof host_features_le);
+        fw_cfg_add_file(fw_cfg, "etc/smi/supported-features",
+                        lpc->smi_host_features_le,
+                        sizeof lpc->smi_host_features_le);
+
+        /* The other two guest-visible fields are cleared on device reset, we
+         * just link them into fw_cfg here.
+         */
+        fw_cfg_add_file_callback(fw_cfg, "etc/smi/requested-features",
+                                 NULL, NULL,
+                                 lpc->smi_guest_features_le,
+                                 sizeof lpc->smi_guest_features_le,
+                                 false);
+        fw_cfg_add_file_callback(fw_cfg, "etc/smi/features-ok",
+                                 smi_features_ok_callback, lpc,
+                                 &lpc->smi_features_ok,
+                                 sizeof lpc->smi_features_ok,
+                                 true);
+    }
+
     ich9_lpc_reset(&lpc->d.qdev);
 }
 
@@ -507,6 +558,10 @@  static void ich9_lpc_reset(DeviceState *qdev)
 
     lpc->sci_level = 0;
     lpc->rst_cnt = 0;
+
+    memset(lpc->smi_guest_features_le, 0, sizeof lpc->smi_guest_features_le);
+    lpc->smi_features_ok = 0;
+    lpc->smi_negotiated_features = 0;
 }
 
 /* root complex register block is mapped into memory space */
@@ -668,6 +723,29 @@  static const VMStateDescription vmstate_ich9_rst_cnt = {
     }
 };
 
+static bool ich9_smi_feat_needed(void *opaque)
+{
+    ICH9LPCState *lpc = opaque;
+
+    return !buffer_is_zero(lpc->smi_guest_features_le,
+                           sizeof lpc->smi_guest_features_le) ||
+           lpc->smi_features_ok;
+}
+
+static const VMStateDescription vmstate_ich9_smi_feat = {
+    .name = "ICH9LPC/smi_feat",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = ich9_smi_feat_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT8_ARRAY(smi_guest_features_le, ICH9LPCState,
+                            sizeof(uint64_t)),
+        VMSTATE_UINT8(smi_features_ok, ICH9LPCState),
+        VMSTATE_UINT64(smi_negotiated_features, ICH9LPCState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const VMStateDescription vmstate_ich9_lpc = {
     .name = "ICH9LPC",
     .version_id = 1,
@@ -683,6 +761,7 @@  static const VMStateDescription vmstate_ich9_lpc = {
     },
     .subsections = (const VMStateDescription*[]) {
         &vmstate_ich9_rst_cnt,
+        &vmstate_ich9_smi_feat,
         NULL
     }
 };