Re: [PATCH v2] KVM: vmx: Set msr bitmap correctly if vcpu is in guest mode

From: Bandan Das
Date: Wed Mar 04 2015 - 10:59:06 EST


Hi Wincy,

Wincy Van <fanwenyi0529@xxxxxxxxx> writes:

> In commit 3af18d9c5fe9 ("KVM: nVMX: Prepare for using hardware MSR bitmap"),
> we are setting MSR_BITMAP in prepare_vmcs02 if we should use hardware. This
> is not enough since the field will be modified by following vmx_set_efer.
>
> Fix this by setting vmx_msr_bitmap_nested in vmx_set_msr_bitmap if vcpu is
> in guest mode.
>
> Signed-off-by: Wincy Van <fanwenyi0529@xxxxxxxxx>
> ---
> arch/x86/kvm/vmx.c | 11 +++++++----
> 1 files changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index f7b20b4..10a481b 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2168,7 +2168,10 @@ static void vmx_set_msr_bitmap(struct kvm_vcpu *vcpu)
> {
> unsigned long *msr_bitmap;
>
> - if (irqchip_in_kernel(vcpu->kvm) && apic_x2apic_mode(vcpu->arch.apic)) {
> + if (is_guest_mode(vcpu))
> + msr_bitmap = vmx_msr_bitmap_nested;
Do you think this should be (is_guest_mode(vcpu) &
(exec_control & CPU_BASED_USE_MSR_BITMAPS)) ?

> + else if (irqchip_in_kernel(vcpu->kvm) &&
> + apic_x2apic_mode(vcpu->arch.apic)) {
> if (is_long_mode(vcpu))
> msr_bitmap = vmx_msr_bitmap_longmode_x2apic;
> else
> @@ -9218,9 +9221,9 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
> }
>
> if (cpu_has_vmx_msr_bitmap() &&
> - exec_control & CPU_BASED_USE_MSR_BITMAPS &&
> - nested_vmx_merge_msr_bitmap(vcpu, vmcs12)) {
> - vmcs_write64(MSR_BITMAP, __pa(vmx_msr_bitmap_nested));
> + exec_control & CPU_BASED_USE_MSR_BITMAPS) {
> + nested_vmx_merge_msr_bitmap(vcpu, vmcs12);
> + /* MSR_BITMAP will be set by following vmx_set_efer. */
> } else
> exec_control &= ~CPU_BASED_USE_MSR_BITMAPS;
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/