[05/26] KVM: x86: remove vcpu's CPL check in host-invoked XCR set

From: Ben Hutchings
Date: Tue Jun 25 2013 - 22:51:16 EST


3.2.48-rc1 review patch. If anyone has any objections, please let me know.

------------------

From: "Zhanghaoyu (A)" <haoyu.zhang@xxxxxxxxxx>

commit 764bcbc5a6d7a2f3e75c9f0e4caa984e2926e346 upstream.

__kvm_set_xcr function does the CPL check when set xcr. __kvm_set_xcr is
called in two flows, one is invoked by guest, call stack shown as below,

handle_xsetbv(or xsetbv_interception)
kvm_set_xcr
__kvm_set_xcr

the other one is invoked by host, for example during system reset:

kvm_arch_vcpu_ioctl
kvm_vcpu_ioctl_x86_set_xcrs
__kvm_set_xcr

The former does need the CPL check, but the latter does not.

Signed-off-by: Zhang Haoyu <haoyu.zhang@xxxxxxxxxx>
[Tweaks to commit message. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -551,8 +551,6 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu,
if (index != XCR_XFEATURE_ENABLED_MASK)
return 1;
xcr0 = xcr;
- if (kvm_x86_ops->get_cpl(vcpu) != 0)
- return 1;
if (!(xcr0 & XSTATE_FP))
return 1;
if ((xcr0 & XSTATE_YMM) && !(xcr0 & XSTATE_SSE))
@@ -566,7 +564,8 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu,

int kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
{
- if (__kvm_set_xcr(vcpu, index, xcr)) {
+ if (kvm_x86_ops->get_cpl(vcpu) != 0 ||
+ __kvm_set_xcr(vcpu, index, xcr)) {
kvm_inject_gp(vcpu, 0);
return 1;
}

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