linux-kernel - [PATCH] KVM: x86: Handle MXCSR in kvm_arch_vcpu_ioctl_{get,set}

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Message-Id: <20220917000928.118-1-justinien.bouron@gmail.com>
Date:   Sat, 17 Sep 2022 00:09:28 +0000
From:   Justinien Bouron <justinien.bouron@...il.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     Justinien Bouron <justinien.bouron@...il.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: x86: Handle MXCSR in kvm_arch_vcpu_ioctl_{get,set}_fpu.

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@...il.com>
---
 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