Re: [PATCH 1/2] KVM: VMX: Use kvm_read_cr4() to get cr4 value

[Xiaoyao Li]

On 4/12/2023 11:03 PM, Sean Christopherson wrote:
> On Wed, Apr 12, 2023, Xiaoyao Li wrote:
> > On 4/11/2023 1:11 AM, Sean Christopherson wrote:
> > > On Mon, Apr 10, 2023, Xiaoyao Li wrote:
> > > > Directly use vcpu->arch.cr4 is not recommended since it gets stale value
> > > > if the cr4 is not available.
> > > >
> > > > Use kvm_read_cr4() instead to ensure correct value.
> > > >
> > > > Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> > > > ---
> > > >    arch/x86/kvm/vmx/vmx.c | 2 +-
> > > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > > > index d7bf14abdba1..befa2486836b 100644
> > > > --- a/arch/x86/kvm/vmx/vmx.c
> > > > +++ b/arch/x86/kvm/vmx/vmx.c
> > > > @@ -3431,7 +3431,7 @@ static bool vmx_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
> > > >    void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
> > > >    {
> > > > -	unsigned long old_cr4 = vcpu->arch.cr4;
> > > > +	unsigned long old_cr4 = kvm_read_cr4(vcpu);
> > >
> > > Ha!  I've been tempted to change this multiple times, but always thought I was
> > > just being a bit obsessive :-)
> > >
> > > Patches look good, but I'm going to hold them for 6.5 just in case this somehow
> > > causes a problem, e.g. if there's a bizzaro nested path that "works" because KVM
> > > _doesn't_ decache info from the current VMCS.
> >
> > so you will put it in kvm-next after 6.4 merge windows?
>
> The likely candidate is "kvm-x86 vmx", and I probably won't apply the patches until
> after v6.4-rc2 (rc2 being my preferred base for the next cycle).  But yes, the plan
> is to apply the patches after the 6.4 merge window.
>
> Are you asking because you want to know if you need to resend for 6.5?  Or does
> the timing/location matter for some other reason, e.g. a dependency from another
> patch/series?

none of it. Just to confirm I get it. :)