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SubjectRe: [PATCH 2/2] KVM: x86: fix KVM_SET_XCRS loop
On Thu, Oct 17, 2013 at 04:50:47PM +0200, Paolo Bonzini wrote:
> The loop was always using 0 as the index. This means that
> any rubbish after the first element of the array went undetected.
> It seems reasonable to assume that no KVM userspace did that.

It is not a typo, look at __kvm_set_xcr when setting
guest_xcrs->xcrs[i].value, with i != 0.

The code is not prepared to deal with XCR != 0 (because its not
implemented in hw).

> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/kvm/x86.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f4e1391..f91dff2 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3062,9 +3062,9 @@ static int kvm_vcpu_ioctl_x86_set_xcrs(struct kvm_vcpu *vcpu,
>
> for (i = 0; i < guest_xcrs->nr_xcrs; i++)
> /* Only support XCR0 currently */
> - if (guest_xcrs->xcrs[0].xcr == XCR_XFEATURE_ENABLED_MASK) {
> + if (guest_xcrs->xcrs[i].xcr == XCR_XFEATURE_ENABLED_MASK) {
> r = __kvm_set_xcr(vcpu, XCR_XFEATURE_ENABLED_MASK,
> - guest_xcrs->xcrs[0].value);
> + guest_xcrs->xcrs[i].value);
> break;
> }
> if (r)
> --
> 1.8.3.1


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