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    Subject[PATCH 21/39] KVM: VMX: Give the guest ownership of cr0.ts when the fpu is active
    Date
    If the guest fpu is loaded, there is nothing interesing about cr0.ts; let
    the guest play with it as it will. This makes context switches between fpu
    intensive guest processes faster, as we won't trap the clts and cr0 write
    instructions.

    [marcelo: fix cr0 read shadow update on fpu deactivation; kills F8 install]

    Signed-off-by: Avi Kivity <avi@redhat.com>
    Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
    ---
    arch/x86/kvm/vmx.c | 11 +++++++++--
    1 files changed, 9 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
    index d11be3f..fc1964d 100644
    --- a/arch/x86/kvm/vmx.c
    +++ b/arch/x86/kvm/vmx.c
    @@ -803,12 +803,20 @@ static void vmx_fpu_activate(struct kvm_vcpu *vcpu)
    if (kvm_read_cr0_bits(vcpu, X86_CR0_TS))
    vmcs_set_bits(GUEST_CR0, X86_CR0_TS);
    update_exception_bitmap(vcpu);
    + vcpu->arch.cr0_guest_owned_bits = X86_CR0_TS;
    + vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits);
    }

    +static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu);
    +
    static void vmx_fpu_deactivate(struct kvm_vcpu *vcpu)
    {
    + vmx_decache_cr0_guest_bits(vcpu);
    vmcs_set_bits(GUEST_CR0, X86_CR0_TS);
    update_exception_bitmap(vcpu);
    + vcpu->arch.cr0_guest_owned_bits = 0;
    + vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits);
    + vmcs_writel(CR0_READ_SHADOW, vcpu->arch.cr0);
    }

    static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu)
    @@ -2996,8 +3004,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
    };
    break;
    case 2: /* clts */
    - vcpu->arch.cr0 &= ~X86_CR0_TS;
    - vmcs_writel(CR0_READ_SHADOW, kvm_read_cr0(vcpu));
    + vmx_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS));
    trace_kvm_cr_write(0, kvm_read_cr0(vcpu));
    skip_emulated_instruction(vcpu);
    return 1;
    --
    1.6.5.3


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