linux-kernel - Re: [PATCH 1/2] kvm/x86/vmx: enable X86_FEATURE

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Message-ID: <6d6d38a6f62e0d6d093713703e9f0e183c7eda13.camel@redhat.com>
Date:   Wed, 27 May 2020 18:16:47 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Tao Xu <tao3.xu@...el.com>,
        Jim Mattson <jmattson@...gle.com>,
        linux-kernel@...r.kernel.org, Joerg Roedel <joro@...tes.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Wanpeng Li <wanpengli@...cent.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jingqi Liu <jingqi.liu@...el.com>
Subject: Re: [PATCH 1/2] kvm/x86/vmx: enable X86_FEATURE_WAITPKG in KVM
 capabilities

On Tue, 2020-05-26 at 18:20 -0700, Sean Christopherson wrote:
> On Sat, May 23, 2020 at 07:14:54PM +0300, Maxim Levitsky wrote:
> > Even though we might not allow the guest to use
> > WAITPKG's new instructions, we should tell KVM
> > that the feature is supported by the host CPU.
> > 
> > Note that vmx_waitpkg_supported checks that WAITPKG
> > _can_ be set in secondary execution controls as specified
> > by VMX capability MSR, rather that we actually enable it for a
> > guest.
> 
> These line wraps are quite weird and inconsistent.
Known issue for me, I usually don't have line wrapping enabled,
and I wrap the lines a bit earlier that 72 character limit. 
I'll re-formatted the commit message to be on 72 line format and I will
try now to pay much more attention to that.

> 
> > Fixes: e69e72faa3a0 KVM: x86: Add support for user wait
> > instructions
> 
> Checkpatch doesn't complain,  but the preferred Fixes format is
> 
>   Fixes: e69e72faa3a07 ("KVM: x86: Add support for user wait
> instructions")


> 
> e.g.
> 
>   git show -s --pretty='tformat:%h ("%s")'

Got it, and added to git aliases :-)

> 
> For the code itself:
> 
> Reviewed-by: Sean Christopherson <sean.j.christopherson@...el.com>
Thank you!

> 
> > Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
> > Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> > ---
> >  arch/x86/kvm/vmx/vmx.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index 55712dd86bafa..fca493d4517c5 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -7298,6 +7298,9 @@ static __init void vmx_set_cpu_caps(void)
> >  	/* CPUID 0x80000001 */
> >  	if (!cpu_has_vmx_rdtscp())
> >  		kvm_cpu_cap_clear(X86_FEATURE_RDTSCP);
> > +
> > +	if (vmx_waitpkg_supported())
> > +		kvm_cpu_cap_check_and_set(X86_FEATURE_WAITPKG);
> >  }
> >  
> >  static void vmx_request_immediate_exit(struct kvm_vcpu *vcpu)
> > -- 
> > 2.26.2
> >