Re: [RFC Part1 PATCH 01/13] x86/cpufeatures: Add SEV-SNP CPU feature

Brijesh Singh
2021-03-25T14:51:07Z

On 3/25/21 5:54 AM, Borislav Petkov wrote:
> On Wed, Mar 24, 2021 at 11:44:12AM -0500, Brijesh Singh wrote:
>> Add CPU feature detection for Secure Encrypted Virtualization with
>> Secure Nested Paging. This feature adds a strong memory integrity
>> protection to help prevent malicious hypervisor-based attacks like
>> data replay, memory re-mapping, and more.
>>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Borislav Petkov <bp@alien8.de>
>> Cc: Joerg Roedel <jroedel@suse.de>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Cc: Tony Luck <tony.luck@intel.com>
>> Cc: Dave Hansen <dave.hansen@intel.com>
>> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Tom Lendacky <thomas.lendacky@amd.com>
>> Cc: David Rientjes <rientjes@google.com>
>> Cc: Sean Christopherson <seanjc@google.com>
>> Cc: x86@kernel.org
>> Cc: kvm@vger.kernel.org
>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
>> ---
>> arch/x86/include/asm/cpufeatures.h | 1 +
>> arch/x86/kernel/cpu/amd.c | 3 ++-
>> arch/x86/kernel/cpu/scattered.c | 1 +
>> 3 files changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
>> index 84b887825f12..a5b369f10bcd 100644
>> --- a/arch/x86/include/asm/cpufeatures.h
>> +++ b/arch/x86/include/asm/cpufeatures.h
>> @@ -238,6 +238,7 @@
>> #define X86_FEATURE_VMW_VMMCALL ( 8*32+19) /* "" VMware prefers VMMCALL hypercall instruction */
>> #define X86_FEATURE_SEV_ES ( 8*32+20) /* AMD Secure Encrypted Virtualization - Encrypted State */
>> #define X86_FEATURE_VM_PAGE_FLUSH ( 8*32+21) /* "" VM Page Flush MSR is supported */
>> +#define X86_FEATURE_SEV_SNP ( 8*32+22) /* AMD Secure Encrypted Virtualization - Secure Nested Paging */
> That leaf got a separate word now: word 19.
>
> For the future: pls redo your patches against tip/master because it has
> the latest state of affairs in tip-land.

For the early feedback I was trying to find one tree which can be used
for building both the guest and hypervisor at once. In future, I will
submit the part-1 against the tip/master and part-2 against the
kvm/master. thanks

>
>> /* Intel-defined CPU features, CPUID level 0x00000007:0 (EBX), word 9 */
>> #define X86_FEATURE_FSGSBASE ( 9*32+ 0) /* RDFSBASE, WRFSBASE, RDGSBASE, WRGSBASE instructions*/
>> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
>> index f8ca66f3d861..39f7a4b5b04c 100644
>> --- a/arch/x86/kernel/cpu/amd.c
>> +++ b/arch/x86/kernel/cpu/amd.c
>> @@ -586,7 +586,7 @@ static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)
>> * If BIOS has not enabled SME then don't advertise the
>> * SME feature (set in scattered.c).
>> * For SEV: If BIOS has not enabled SEV then don't advertise the
>> - * SEV and SEV_ES feature (set in scattered.c).
>> + * SEV, SEV_ES and SEV_SNP feature (set in scattered.c).
> So you can remove the "scattered.c" references in the comments here.
>
>> *
>> * In all cases, since support for SME and SEV requires long mode,
>> * don't advertise the feature under CONFIG_X86_32.
>> @@ -618,6 +618,7 @@ static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)
>> clear_sev:
>> setup_clear_cpu_cap(X86_FEATURE_SEV);
>> setup_clear_cpu_cap(X86_FEATURE_SEV_ES);
>> + setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
>> }
>> }
>>
>> diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
>> index 236924930bf0..eaec1278dc2e 100644
>> --- a/arch/x86/kernel/cpu/scattered.c
>> +++ b/arch/x86/kernel/cpu/scattered.c
>> @@ -45,6 +45,7 @@ static const struct cpuid_bit cpuid_bits[] = {
>> { X86_FEATURE_SEV_ES, CPUID_EAX, 3, 0x8000001f, 0 },
>> { X86_FEATURE_SME_COHERENT, CPUID_EAX, 10, 0x8000001f, 0 },
>> { X86_FEATURE_VM_PAGE_FLUSH, CPUID_EAX, 2, 0x8000001f, 0 },
>> + { X86_FEATURE_SEV_SNP, CPUID_EAX, 4, 0x8000001f, 0 },
>> { 0, 0, 0, 0, 0 }
>> };
> And this too.
>
> Thx.
>