[PATCH v2 for-4.14-stable] x86,kvm: remove extra kvm_{get,put}_guest_fpu

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Commit 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out
to vcpu_run") applied a patch from upstream, but it appears that it
wasn't backported correctly to 4.14.  The extra out_fpu label and
kvm_put_guest_fpu() added in kvm_arch_vcpu_ioctl_run() result in calling
kvm_put_guest_fpu() twice in a row, corrupting guest state.
Additionally, a duplicate kvm_load_guest_fpu() is added in the middle of
the function.

Fixes: 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run")
Signed-off-by: Daniel Verkamp <dverkamp@xxxxxxxxxxxx>
---

v2: removed additional redundant kvm_load_guest_fpu()

I'm unsure if this is the right way to send this fix - there is no
corresponding mainline commit to reference, since the code there is
already correct, and the problem was introduced in the cherry-picked
stable backport.  Please let me know if there's a different process for
fixes to stable-only issues.

---

 arch/x86/kvm/x86.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 130be2efafbe..af7ab2c71786 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7423,14 +7423,12 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 		}
 	}
 
-	kvm_load_guest_fpu(vcpu);
-
 	if (unlikely(vcpu->arch.complete_userspace_io)) {
 		int (*cui)(struct kvm_vcpu *) = vcpu->arch.complete_userspace_io;
 		vcpu->arch.complete_userspace_io = NULL;
 		r = cui(vcpu);
 		if (r <= 0)
-			goto out_fpu;
+			goto out;
 	} else
 		WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
 
@@ -7439,8 +7437,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	else
 		r = vcpu_run(vcpu);
 
-out_fpu:
-	kvm_put_guest_fpu(vcpu);
 out:
 	kvm_put_guest_fpu(vcpu);
 	post_kvm_run_save(vcpu);
-- 
2.20.1.495.gaa96b0ce6b-goog




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