Re: [PATCH v1 2/6] KVM: x86: Virtualize CR4.LASS

[Zeng Guang <guang.zeng@intel.com>]

On 6/5/2023 9:57 AM, Binbin Wu wrote:
>
> On 6/1/2023 10:23 PM, Zeng Guang wrote:
>> Virtualize CR4.LASS[bit 27] under KVM control instead of being guest-owned
>> as CR4.LASS generally set once for each vCPU at boot time and won't be
>> toggled at runtime. Besides, only if VM has LASS capability enumerated with
>> CPUID.(EAX=07H.ECX=1):EAX.LASS[bit 6], KVM allows guest software to be able
>> to set CR4.LASS.
>>
>> Updating cr4_fixed1 to set CR4.LASS bit in the emulated IA32_VMX_CR4_FIXED1
>> MSR for guests and allow guests to enable LASS in nested VMX operaion as well.
> s/operaion/operation
Thanks.
>
>> Notes: Setting CR4.LASS to 1 enable LASS in IA-32e mode. It doesn't take
>> effect in legacy mode even if CR4.LASS is set.
>>
>> Signed-off-by: Zeng Guang <guang.zeng@intel.com>
>> Tested-by: Xuelian Guo <xuelian.guo@intel.com>
>> ---
>>    arch/x86/include/asm/kvm_host.h | 2 +-
>>    arch/x86/kvm/vmx/vmx.c          | 3 +++
>>    arch/x86/kvm/x86.h              | 2 ++
>>    3 files changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index fb9d1f2d6136..92d8e65fe88c 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -125,7 +125,7 @@
>>    			  | X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR | X86_CR4_PCIDE \
>>    			  | X86_CR4_OSXSAVE | X86_CR4_SMEP | X86_CR4_FSGSBASE \
>>    			  | X86_CR4_OSXMMEXCPT | X86_CR4_LA57 | X86_CR4_VMXE \
>> -			  | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP))
>> +			  | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP | X86_CR4_LASS))
> Suppose there is some bare-matel linux patch to define the LASS related
> macros.
> May be better to describe the dependent patch(es) in cover letter.
>
Good suggestion.