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

[Zeng Guang]

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@xxxxxxxxx>
> > Tested-by: Xuelian Guo <xuelian.guo@xxxxxxxxx>
> > ---
> >    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.