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SubjectRe: [PATCH v6 26/34] iommu/amd: Allow the AMD IOMMU to work with memory encryption
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On 6/7/2017 9:38 PM, Nick Sarnie wrote:
> On Wed, Jun 7, 2017 at 3:17 PM, Tom Lendacky <thomas.lendacky@amd.com> wrote:
>> The IOMMU is programmed with physical addresses for the various tables
>> and buffers that are used to communicate between the device and the
>> driver. When the driver allocates this memory it is encrypted. In order
>> for the IOMMU to access the memory as encrypted the encryption mask needs
>> to be included in these physical addresses during configuration.
>>
>> The PTE entries created by the IOMMU should also include the encryption
>> mask so that when the device behind the IOMMU performs a DMA, the DMA
>> will be performed to encrypted memory.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> ---
>> arch/x86/include/asm/mem_encrypt.h | 7 +++++++
>> arch/x86/mm/mem_encrypt.c | 30 ++++++++++++++++++++++++++++++
>> drivers/iommu/amd_iommu.c | 36 +++++++++++++++++++-----------------
>> drivers/iommu/amd_iommu_init.c | 18 ++++++++++++------
>> drivers/iommu/amd_iommu_proto.h | 10 ++++++++++
>> drivers/iommu/amd_iommu_types.h | 2 +-
>> include/asm-generic/mem_encrypt.h | 5 +++++
>> 7 files changed, 84 insertions(+), 24 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
>> index c7a2525..d86e544 100644
>> --- a/arch/x86/include/asm/mem_encrypt.h
>> +++ b/arch/x86/include/asm/mem_encrypt.h
>> @@ -31,6 +31,8 @@ void __init sme_early_decrypt(resource_size_t paddr,
>>
>> void __init sme_early_init(void);
>>
>> +bool sme_iommu_supported(void);
>> +
>> /* Architecture __weak replacement functions */
>> void __init mem_encrypt_init(void);
>>
>> @@ -62,6 +64,11 @@ static inline void __init sme_early_init(void)
>> {
>> }
>>
>> +static inline bool sme_iommu_supported(void)
>> +{
>> + return true;
>> +}
>> +
>> #endif /* CONFIG_AMD_MEM_ENCRYPT */
>>
>> static inline bool sme_active(void)
>> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
>> index 5d7c51d..018b58a 100644
>> --- a/arch/x86/mm/mem_encrypt.c
>> +++ b/arch/x86/mm/mem_encrypt.c
>> @@ -197,6 +197,36 @@ void __init sme_early_init(void)
>> protection_map[i] = pgprot_encrypted(protection_map[i]);
>> }
>>
>> +bool sme_iommu_supported(void)
>> +{
>> + struct cpuinfo_x86 *c = &boot_cpu_data;
>> +
>> + if (!sme_me_mask || (c->x86 != 0x17))
>> + return true;
>> +
>> + /* For Fam17h, a specific level of support is required */
>> + switch (c->microcode & 0xf000) {
>> + case 0x0000:
>> + return false;
>> + case 0x1000:
>> + switch (c->microcode & 0x0f00) {
>> + case 0x0000:
>> + return false;
>> + case 0x0100:
>> + if ((c->microcode & 0xff) < 0x26)
>> + return false;
>> + break;
>> + case 0x0200:
>> + if ((c->microcode & 0xff) < 0x05)
>> + return false;
>> + break;
>> + }
>> + break;
>> + }
>> +
>> + return true;
>> +}
>> +
>> /* Architecture __weak replacement functions */
>> void __init mem_encrypt_init(void)
>> {
>

...

>
> Hi Tom,
>
> This sounds like a cool feature. I'm trying to test it on my Ryzen
> system, but c->microcode & 0xf000 is evaluating as 0, so IOMMU is not
> being enabled on my system. I'm using the latest microcode for AGESA
> 1.0.0.6, 0x08001126. Is this work reliant on a future microcode
> update, or is there some other issue?

This is my mistake. I moved the check and didn't re-test. At this point
the c->microcode field hasn't been filled in so I'll need to read
MSR_AMD64_PATCH_LEVEL directly in the sme_iommu_supported() function.

Thanks,
Tom

>
> Thanks,
> Sarnex
>

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