Re: [PATCH v16 21/51] KVM: x86/mmu: WARN on attempt to check permissions for Shadow Stack #PF

Xiaoyao Li
2025-09-23T14:33:13Z

On 9/22/2025 3:46 PM, Binbin Wu wrote:
>
>
> On 9/22/2025 3:17 PM, Binbin Wu wrote:
>>
>>
>> On 9/20/2025 6:32 AM, Sean Christopherson wrote:
>>> Add PFERR_SS_MASK, a.k.a. Shadow Stack access, and WARN if KVM
>>> attempts to
>>> check permissions for a Shadow Stack access as KVM hasn't been taught to
>>> understand the magic Writable=0,Dirty=0 combination that is required for
> Typo:
>
> Writable=0,Dirty=0 -> Writable=0,Dirty=1

With it fixed,

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>

>>> Shadow Stack accesses, and likely will never learn.  There are no
>>> plans to
>>> support Shadow Stacks with the Shadow MMU, and the emulator rejects all
>>> instructions that affect Shadow Stacks, i.e. it should be impossible for
>>> KVM to observe a #PF due to a shadow stack access.
>>>
>>> Signed-off-by: Sean Christopherson <seanjc@google.com>
>>
>> Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>