linux-kernel - Re: [PATCH 2/2] KVM: X86: XCR0 should be set to the fixed value on vCPU reset

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Message-ID: <CALMp9eQH_mV_AGZ1L1OP_0Eus0LJ7qL6fAJ3g0WDbTO36vJYmA@mail.gmail.com>
Date:   Sun, 8 Oct 2017 15:36:37 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH 2/2] KVM: X86: XCR0 should be set to the fixed value on
 vCPU reset

Reviewed-by: Jim Mattson <jmattson@...gle.com>

On Sat, Oct 7, 2017 at 7:35 PM, Wanpeng Li <kernellwp@...il.com> wrote:
> From: Wanpeng Li <wanpeng.li@...mail.com>
>
> SDM section 2.6 mentioned:
>
> After reset, all bits (except bit 0) in XCR0 are cleared to zero; XCR0[0] is set to 1.
>
> This patch sets XCRO to the 0x1 after vCPU reset.
>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
> ---
>  arch/x86/kvm/x86.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b0d2915..c784cd6 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7816,6 +7816,8 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>         vcpu->arch.regs_avail = ~0;
>         vcpu->arch.regs_dirty = ~0;
>
> +       vcpu->arch.xcr0 = XFEATURE_MASK_FP;
> +
>         kvm_x86_ops->vcpu_reset(vcpu, init_event);
>  }
>
> --
> 2.7.4
>