[PATCH] KVM: x86: Handle MXCSR in kvm_arch_vcpu_ioctl_{get,set}_fpu.

From: Justinien Bouron
Date: Fri Sep 16 2022 - 20:10:33 EST


kvm_arch_vcpu_ioctl_get_fpu does not set the mxcsr in the kvm_fpu
struct; conversely kvm_arch_vcpu_ioctl_set_fpu does not set the mxcsr
value in the fxregs_state struct of the vcpu.
This leads to the KVM_GET_FPU ioctl returning 0 as the mxcsr value,
regardless of the actual value on the vcpu; while KVM_SET_FPU leaves the
MXCSR on the vcpu untouched.

Fix kvm_arch_vcpu_ioctl_{get,set}_fpu to properly handle MXCSR.

Signed-off-by: Justinien Bouron <justinien.bouron@xxxxxxxxx>
---
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 43a6a7efc6ec..c33a2599a497 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11462,6 +11462,7 @@ int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
fpu->last_ip = fxsave->rip;
fpu->last_dp = fxsave->rdp;
memcpy(fpu->xmm, fxsave->xmm_space, sizeof(fxsave->xmm_space));
+ fpu->mxcsr = fxsave->mxcsr;

vcpu_put(vcpu);
return 0;
@@ -11486,6 +11487,7 @@ int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
fxsave->rip = fpu->last_ip;
fxsave->rdp = fpu->last_dp;
memcpy(fxsave->xmm_space, fpu->xmm, sizeof(fxsave->xmm_space));
+ fxsave->mxcsr = fpu->mxcsr;

vcpu_put(vcpu);
return 0;
--
2.25.1