diff mbox series

[v9,29/43] x86/boot: Add Confidential Computing type to setup_data

Message ID 20220128171804.569796-30-brijesh.singh@amd.com
State Superseded
Headers show
Series Add AMD Secure Nested Paging (SEV-SNP) Guest Support | expand

Commit Message

Brijesh Singh Jan. 28, 2022, 5:17 p.m. UTC
While launching the encrypted guests, the hypervisor may need to provide
some additional information during the guest boot. When booting under the
EFI based BIOS, the EFI configuration table contains an entry for the
confidential computing blob that contains the required information.

To support booting encrypted guests on non-EFI VM, the hypervisor needs to
pass this additional information to the kernel with a different method.

For this purpose, introduce SETUP_CC_BLOB type in setup_data to hold the
physical address of the confidential computing blob location. The boot
loader or hypervisor may choose to use this method instead of EFI
configuration table. The CC blob location scanning should give preference
to setup_data data over the EFI configuration table.

In AMD SEV-SNP, the CC blob contains the address of the secrets and CPUID
pages. The secrets page includes information such as a VM to PSP
communication key and CPUID page contains PSP filtered CPUID values.
Define the AMD SEV confidential computing blob structure.

While at it, define the EFI GUID for the confidential computing blob.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 arch/x86/include/asm/sev.h            | 18 ++++++++++++++++++
 arch/x86/include/uapi/asm/bootparam.h |  1 +
 include/linux/efi.h                   |  1 +
 3 files changed, 20 insertions(+)

Comments

Borislav Petkov Feb. 4, 2022, 4:21 p.m. UTC | #1
On Fri, Jan 28, 2022 at 11:17:50AM -0600, Brijesh Singh wrote:
> +/*
> + * AMD SEV Confidential computing blob structure. The structure is
> + * defined in OVMF UEFI firmware header:
> + * https://github.com/tianocore/edk2/blob/master/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h

So looking at that typedef struct CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION there:

typedef struct {
  UINT32    Header;
  UINT16    Version;
  UINT16    Reserved1;
  UINT64    SecretsPhysicalAddress;
  UINT32    SecretsSize;
  UINT64    CpuidPhysicalAddress;
  UINT32    CpuidLSize;
} CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION;

> + */
> +#define CC_BLOB_SEV_HDR_MAGIC	0x45444d41
> +struct cc_blob_sev_info {
> +	u32 magic;

That's called "Header" there.

> +	u16 version;
> +	u16 reserved;
> +	u64 secrets_phys;
> +	u32 secrets_len;
> +	u32 rsvd1;

You've added that member for padding but the fw blob one doesn't have
it.

But if we get a blob from the firmware and the structure layout differs,
how is this supposed to even work?

> +	u64 cpuid_phys;
> +	u32 cpuid_len;
> +	u32 rsvd2;

That one too.

Or are you going to change the blob layout in ovmf too, to match?
Brijesh Singh Feb. 4, 2022, 5:41 p.m. UTC | #2
On 2/4/22 10:21 AM, Borislav Petkov wrote:
> On Fri, Jan 28, 2022 at 11:17:50AM -0600, Brijesh Singh wrote:
>> +/*
>> + * AMD SEV Confidential computing blob structure. The structure is
>> + * defined in OVMF UEFI firmware header:
>> + * https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Ftianocore%2Fedk2%2Fblob%2Fmaster%2FOvmfPkg%2FInclude%2FGuid%2FConfidentialComputingSevSnpBlob.h&amp;data=04%7C01%7Cbrijesh.singh%40amd.com%7C334b7454d7a541f3497d08d9e7fa796c%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637795885258984697%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=XNPvA7re7WHpAgzeuOC%2Buu0ql18P6KOIbP5ZriFsxEY%3D&amp;reserved=0
> So looking at that typedef struct CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION there:
>
> typedef struct {
>   UINT32    Header;
>   UINT16    Version;
>   UINT16    Reserved1;
>   UINT64    SecretsPhysicalAddress;
>   UINT32    SecretsSize;
>   UINT64    CpuidPhysicalAddress;
>   UINT32    CpuidLSize;
> } CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION;
>
>> + */
>> +#define CC_BLOB_SEV_HDR_MAGIC	0x45444d41
>> +struct cc_blob_sev_info {
>> +	u32 magic;
> That's called "Header" there.

I will rename it to keep it consistent with OVMF header.


>> +	u16 version;
>> +	u16 reserved;
>> +	u64 secrets_phys;
>> +	u32 secrets_len;
>> +	u32 rsvd1;
> You've added that member for padding but the fw blob one doesn't have
> it.
>
> But if we get a blob from the firmware and the structure layout differs,
> how is this supposed to even work?
>
>> +	u64 cpuid_phys;
>> +	u32 cpuid_len;
>> +	u32 rsvd2;
> That one too.
>
> Or are you going to change the blob layout in ovmf too, to match?

Yes, that's the plan. I have tested my OVMF with v9 and everything looks
good at the runtime. Will send OVMF patch to match the blob layout.
diff mbox series

Patch

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index a3203b2caaca..1a7e21bb6eea 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -42,6 +42,24 @@  struct es_em_ctxt {
 	struct es_fault_info fi;
 };
 
+/*
+ * AMD SEV Confidential computing blob structure. The structure is
+ * defined in OVMF UEFI firmware header:
+ * https://github.com/tianocore/edk2/blob/master/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
+ */
+#define CC_BLOB_SEV_HDR_MAGIC	0x45444d41
+struct cc_blob_sev_info {
+	u32 magic;
+	u16 version;
+	u16 reserved;
+	u64 secrets_phys;
+	u32 secrets_len;
+	u32 rsvd1;
+	u64 cpuid_phys;
+	u32 cpuid_len;
+	u32 rsvd2;
+};
+
 void do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code);
 
 static inline u64 lower_bits(u64 val, unsigned int bits)
diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index b25d3f82c2f3..1ac5acca72ce 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -10,6 +10,7 @@ 
 #define SETUP_EFI			4
 #define SETUP_APPLE_PROPERTIES		5
 #define SETUP_JAILHOUSE			6
+#define SETUP_CC_BLOB			7
 
 #define SETUP_INDIRECT			(1<<31)
 
diff --git a/include/linux/efi.h b/include/linux/efi.h
index ccd4d3f91c98..984aa688997a 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -390,6 +390,7 @@  void efi_native_runtime_setup(void);
 #define EFI_CERT_SHA256_GUID			EFI_GUID(0xc1c41626, 0x504c, 0x4092, 0xac, 0xa9, 0x41, 0xf9, 0x36, 0x93, 0x43, 0x28)
 #define EFI_CERT_X509_GUID			EFI_GUID(0xa5c059a1, 0x94e4, 0x4aa7, 0x87, 0xb5, 0xab, 0x15, 0x5c, 0x2b, 0xf0, 0x72)
 #define EFI_CERT_X509_SHA256_GUID		EFI_GUID(0x3bd2a492, 0x96c0, 0x4079, 0xb4, 0x20, 0xfc, 0xf9, 0x8e, 0xf1, 0x03, 0xed)
+#define EFI_CC_BLOB_GUID			EFI_GUID(0x067b1f5f, 0xcf26, 0x44c5, 0x85, 0x54, 0x93, 0xd7, 0x77, 0x91, 0x2d, 0x42)
 
 /*
  * This GUID is used to pass to the kernel proper the struct screen_info