[V3,3/5] hyperv/IOMMU: Enable swiotlb bounce buffer for Isolation VM

From: Tianyu Lan <Tianyu.Lan@microsoft.com>

hyperv Isolation VM requires bounce buffer support to copy
data from/to encrypted memory and so enable swiotlb force
mode to use swiotlb bounce buffer for DMA transaction.

In Isolation VM with AMD SEV, the bounce buffer needs to be
accessed via extra address space which is above shared_gpa_boundary
(E.G 39 bit address line) reported by Hyper-V CPUID ISOLATION_CONFIG.
The access physical address will be original physical address +
shared_gpa_boundary. The shared_gpa_boundary in the AMD SEV SNP
spec is called virtual top of memory(vTOM). Memory addresses below
vTOM are automatically treated as private while memory above
vTOM is treated as shared.

Hyper-V initalizes swiotlb bounce buffer and default swiotlb
needs to be disabled. pci_swiotlb_detect_override() and
pci_swiotlb_detect_4gb() enable the default one. To override
the setting, hyperv_swiotlb_detect() needs to run before
these detect functions which depends on the pci_xen_swiotlb_
init(). Make pci_xen_swiotlb_init() depends on the hyperv_swiotlb
_detect() to keep the order.

Swiotlb bounce buffer code calls set_memory_decrypted()
to mark bounce buffer visible to host and map it in extra
address space via memremap. Populate the shared_gpa_boundary
(vTOM) via swiotlb_unencrypted_base variable.

The map function memremap() can't work in the early place
hyperv_iommu_swiotlb_init() and so call swiotlb_update_mem_attributes()
in the hyperv_iommu_swiotlb_later_init().

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
 arch/x86/xen/pci-swiotlb-xen.c |  3 +-
 drivers/hv/vmbus_drv.c         |  3 ++
 drivers/iommu/hyperv-iommu.c   | 56 ++++++++++++++++++++++++++++++++++
 include/linux/hyperv.h         |  8 +++++
 4 files changed, 69 insertions(+), 1 deletion(-)

On Wed, Dec 01, 2021 at 11:02:54AM -0500, Tianyu Lan wrote:
[...]
> diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
> index 46df59aeaa06..30fd0600b008 100644
> --- a/arch/x86/xen/pci-swiotlb-xen.c
> +++ b/arch/x86/xen/pci-swiotlb-xen.c
> @@ -4,6 +4,7 @@
>  
>  #include <linux/dma-map-ops.h>
>  #include <linux/pci.h>
> +#include <linux/hyperv.h>
>  #include <xen/swiotlb-xen.h>
>  
>  #include <asm/xen/hypervisor.h>
> @@ -91,6 +92,6 @@ int pci_xen_swiotlb_init_late(void)
>  EXPORT_SYMBOL_GPL(pci_xen_swiotlb_init_late);
>  
>  IOMMU_INIT_FINISH(pci_xen_swiotlb_detect,
> -		  NULL,
> +		  hyperv_swiotlb_detect,

It is not immediately obvious why this is needed just by reading the
code. Please consider copying some of the text in the commit message to
a comment here.

Thanks,
Wei.

On 12/2/2021 10:43 PM, Wei Liu wrote:
> On Wed, Dec 01, 2021 at 11:02:54AM -0500, Tianyu Lan wrote:
> [...]
>> diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
>> index 46df59aeaa06..30fd0600b008 100644
>> --- a/arch/x86/xen/pci-swiotlb-xen.c
>> +++ b/arch/x86/xen/pci-swiotlb-xen.c
>> @@ -4,6 +4,7 @@
>>   
>>   #include <linux/dma-map-ops.h>
>>   #include <linux/pci.h>
>> +#include <linux/hyperv.h>
>>   #include <xen/swiotlb-xen.h>
>>   
>>   #include <asm/xen/hypervisor.h>
>> @@ -91,6 +92,6 @@ int pci_xen_swiotlb_init_late(void)
>>   EXPORT_SYMBOL_GPL(pci_xen_swiotlb_init_late);
>>   
>>   IOMMU_INIT_FINISH(pci_xen_swiotlb_detect,
>> -		  NULL,
>> +		  hyperv_swiotlb_detect,
> 
> It is not immediately obvious why this is needed just by reading the
> code. Please consider copying some of the text in the commit message to
> a comment here.
> 

Thanks for suggestion. Will update.

From: Tianyu Lan <ltykernel@gmail.com> Sent: Wednesday, December 1, 2021 8:03 AM
> 
> hyperv Isolation VM requires bounce buffer support to copy
> data from/to encrypted memory and so enable swiotlb force
> mode to use swiotlb bounce buffer for DMA transaction.
> 
> In Isolation VM with AMD SEV, the bounce buffer needs to be
> accessed via extra address space which is above shared_gpa_boundary
> (E.G 39 bit address line) reported by Hyper-V CPUID ISOLATION_CONFIG.
> The access physical address will be original physical address +
> shared_gpa_boundary. The shared_gpa_boundary in the AMD SEV SNP
> spec is called virtual top of memory(vTOM). Memory addresses below
> vTOM are automatically treated as private while memory above
> vTOM is treated as shared.
> 
> Hyper-V initalizes swiotlb bounce buffer and default swiotlb
> needs to be disabled. pci_swiotlb_detect_override() and
> pci_swiotlb_detect_4gb() enable the default one. To override
> the setting, hyperv_swiotlb_detect() needs to run before
> these detect functions which depends on the pci_xen_swiotlb_
> init(). Make pci_xen_swiotlb_init() depends on the hyperv_swiotlb
> _detect() to keep the order.
> 
> Swiotlb bounce buffer code calls set_memory_decrypted()
> to mark bounce buffer visible to host and map it in extra
> address space via memremap. Populate the shared_gpa_boundary
> (vTOM) via swiotlb_unencrypted_base variable.
> 
> The map function memremap() can't work in the early place
> hyperv_iommu_swiotlb_init() and so call swiotlb_update_mem_attributes()
> in the hyperv_iommu_swiotlb_later_init().
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
> ---
>  arch/x86/xen/pci-swiotlb-xen.c |  3 +-
>  drivers/hv/vmbus_drv.c         |  3 ++
>  drivers/iommu/hyperv-iommu.c   | 56 ++++++++++++++++++++++++++++++++++
>  include/linux/hyperv.h         |  8 +++++
>  4 files changed, 69 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
> index 46df59aeaa06..30fd0600b008 100644
> --- a/arch/x86/xen/pci-swiotlb-xen.c
> +++ b/arch/x86/xen/pci-swiotlb-xen.c
> @@ -4,6 +4,7 @@
> 
>  #include <linux/dma-map-ops.h>
>  #include <linux/pci.h>
> +#include <linux/hyperv.h>
>  #include <xen/swiotlb-xen.h>
> 
>  #include <asm/xen/hypervisor.h>
> @@ -91,6 +92,6 @@ int pci_xen_swiotlb_init_late(void)
>  EXPORT_SYMBOL_GPL(pci_xen_swiotlb_init_late);
> 
>  IOMMU_INIT_FINISH(pci_xen_swiotlb_detect,
> -		  NULL,
> +		  hyperv_swiotlb_detect,
>  		  pci_xen_swiotlb_init,
>  		  NULL);
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 392c1ac4f819..0a64ccfafb8b 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -33,6 +33,7 @@
>  #include <linux/random.h>
>  #include <linux/kernel.h>
>  #include <linux/syscore_ops.h>
> +#include <linux/dma-map-ops.h>
>  #include <clocksource/hyperv_timer.h>
>  #include "hyperv_vmbus.h"
> 
> @@ -2078,6 +2079,7 @@ struct hv_device *vmbus_device_create(const guid_t *type,
>  	return child_device_obj;
>  }
> 
> +static u64 vmbus_dma_mask = DMA_BIT_MASK(64);
>  /*
>   * vmbus_device_register - Register the child device
>   */
> @@ -2118,6 +2120,7 @@ int vmbus_device_register(struct hv_device *child_device_obj)
>  	}
>  	hv_debug_add_dev_dir(child_device_obj);
> 
> +	child_device_obj->device.dma_mask = &vmbus_dma_mask;
>  	return 0;
> 
>  err_kset_unregister:
> diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c
> index e285a220c913..dd729d49a1eb 100644
> --- a/drivers/iommu/hyperv-iommu.c
> +++ b/drivers/iommu/hyperv-iommu.c
> @@ -13,14 +13,20 @@
>  #include <linux/irq.h>
>  #include <linux/iommu.h>
>  #include <linux/module.h>
> +#include <linux/hyperv.h>
> +#include <linux/io.h>
> 
>  #include <asm/apic.h>
>  #include <asm/cpu.h>
>  #include <asm/hw_irq.h>
>  #include <asm/io_apic.h>
> +#include <asm/iommu.h>
> +#include <asm/iommu_table.h>
>  #include <asm/irq_remapping.h>
>  #include <asm/hypervisor.h>
>  #include <asm/mshyperv.h>
> +#include <asm/swiotlb.h>
> +#include <linux/dma-direct.h>
> 
>  #include "irq_remapping.h"
> 
> @@ -337,4 +343,54 @@ static const struct irq_domain_ops hyperv_root_ir_domain_ops = {
>  	.free = hyperv_root_irq_remapping_free,
>  };
> 
> +static void __init hyperv_iommu_swiotlb_init(void)
> +{
> +	unsigned long hyperv_io_tlb_size;
> +	void *hyperv_io_tlb_start;
> +
> +	/*
> +	 * Allocate Hyper-V swiotlb bounce buffer at early place
> +	 * to reserve large contiguous memory.
> +	 */
> +	hyperv_io_tlb_size = swiotlb_size_or_default();
> +	hyperv_io_tlb_start = memblock_alloc(hyperv_io_tlb_size, PAGE_SIZE);
> +
> +	if (!hyperv_io_tlb_start)
> +		pr_warn("Fail to allocate Hyper-V swiotlb buffer.\n");

In the error case, won't swiotlb_init_with_tlb() end up panic'ing when
it tries to zero out the memory?   The only real choice here is to
return immediately after printing the message, and not call
swiotlb_init_with_tlb().

> +
> +	swiotlb_init_with_tbl(hyperv_io_tlb_start,
> +			      hyperv_io_tlb_size >> IO_TLB_SHIFT, true);
> +}
> +
> +int __init hyperv_swiotlb_detect(void)
> +{
> +	if (!hypervisor_is_type(X86_HYPER_MS_HYPERV))
> +		return 0;
> +
> +	if (!hv_is_isolation_supported())
> +		return 0;
> +
> +	/*
> +	 * Enable swiotlb force mode in Isolation VM to
> +	 * use swiotlb bounce buffer for dma transaction.
> +	 */
> +	if (hv_isolation_type_snp())
> +		swiotlb_unencrypted_base = ms_hyperv.shared_gpa_boundary;
> +	swiotlb_force = SWIOTLB_FORCE;
> +	return 1;
> +}
> +
> +static void __init hyperv_iommu_swiotlb_later_init(void)
> +{
> +	/*
> +	 * Swiotlb bounce buffer needs to be mapped in extra address
> +	 * space. Map function doesn't work in the early place and so
> +	 * call swiotlb_update_mem_attributes() here.
> +	 */
> +	swiotlb_update_mem_attributes();
> +}
> +
> +IOMMU_INIT_FINISH(hyperv_swiotlb_detect,
> +		  NULL, hyperv_iommu_swiotlb_init,
> +		  hyperv_iommu_swiotlb_later_init);
>  #endif
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index b823311eac79..1f037e114dc8 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -1726,6 +1726,14 @@ int hyperv_write_cfg_blk(struct pci_dev *dev, void *buf, unsigned int len,
>  int hyperv_reg_block_invalidate(struct pci_dev *dev, void *context,
>  				void (*block_invalidate)(void *context,
>  							 u64 block_mask));
> +#if IS_ENABLED(CONFIG_HYPERV)
> +int __init hyperv_swiotlb_detect(void);
> +#else
> +static inline int __init hyperv_swiotlb_detect(void)
> +{
> +	return 0;
> +}
> +#endif
> 
>  struct hyperv_pci_block_ops {
>  	int (*read_block)(struct pci_dev *dev, void *buf, unsigned int buf_len,
> --
> 2.25.1

On 12/4/2021 3:17 AM, Michael Kelley (LINUX) wrote:
>> +static void __init hyperv_iommu_swiotlb_init(void)
>> +{
>> +	unsigned long hyperv_io_tlb_size;
>> +	void *hyperv_io_tlb_start;
>> +
>> +	/*
>> +	 * Allocate Hyper-V swiotlb bounce buffer at early place
>> +	 * to reserve large contiguous memory.
>> +	 */
>> +	hyperv_io_tlb_size = swiotlb_size_or_default();
>> +	hyperv_io_tlb_start = memblock_alloc(hyperv_io_tlb_size, PAGE_SIZE);
>> +
>> +	if (!hyperv_io_tlb_start)
>> +		pr_warn("Fail to allocate Hyper-V swiotlb buffer.\n");
> In the error case, won't swiotlb_init_with_tlb() end up panic'ing when
> it tries to zero out the memory?   The only real choice here is to
> return immediately after printing the message, and not call
> swiotlb_init_with_tlb().
> 

Yes, agree. Will update.