linux-kernel - RE: [PATCH RESEND] KVM: x86: Expose CLDEMOTE CPU feature to guest VM

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Date:   Mon, 4 Jun 2018 07:19:31 +0000
From:   "Liu, Jingqi" <jingqi.liu@...el.com>
To:     "pbonzini@...hat.com" <pbonzini@...hat.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Wang, Wei W" <wei.w.wang@...el.com>
Subject: RE: [PATCH RESEND] KVM: x86: Expose CLDEMOTE CPU feature to guest VM

Hi Paolo,

I had changed the Signed-off-by chain.
Could you help to review?
Thanks.

On 5/22/2018 5:01 PM, Liu, Jingqi wrote:

> 
> The CLDEMOTE instruction hints to hardware that the cache line that contains
> the linear address should be moved("demoted") from the cache(s) closest to the
> processor core to a level more distant from the processor core. This may
> accelerate subsequent accesses to the line by other cores in the same coherence
> domain, especially if the line was written by the core that demotes the line.
> 
> This patch exposes the cldemote feature to the guest.
> 
> The release document ref below link:
> https://software.intel.com/sites/default/files/managed/c5/15/\
> architecture-instruction-set-extensions-programming-reference.pdf
> This patch has a dependency on https://lkml.org/lkml/2018/4/23/928
> 
> Signed-off-by: Jingqi Liu <jingqi.liu@...el.com>
> ---
>  arch/x86/kvm/cpuid.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index
> 82055b9..72d8c49 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -403,7 +403,8 @@ static inline int __do_cpuid_ent(struct
> kvm_cpuid_entry2 *entry, u32 function,
>  	const u32 kvm_cpuid_7_0_ecx_x86_features =
>  		F(AVX512VBMI) | F(LA57) | F(PKU) | 0 /*OSPKE*/ |
>  		F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI)
> |
> -		F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) |
> F(AVX512_BITALG);
> +		F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) |
> F(AVX512_BITALG) |
> +		F(CLDEMOTE);
> 
>  	/* cpuid 7.0.edx*/
>  	const u32 kvm_cpuid_7_0_edx_x86_features =
> --
> 1.8.3.1