linux-kernel - [PATCH 3.4 136/146] x86, kvm: use kernel_fpu_begin/end() in kvm_load/put_guest

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Date:	Tue, 15 Sep 2015 17:04:11 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Avi Kivity <avi@...hat.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Rui Xiang <rui.xiang@...wei.com>, Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 136/146] x86, kvm: use kernel_fpu_begin/end() in kvm_load/put_guest_fpu()

From: Suresh Siddha <suresh.b.siddha@...el.com>

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

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


commit 9c1c3fac53378c9782c18f80107965578d7b7167 upstream.

kvm's guest fpu save/restore should be wrapped around
kernel_fpu_begin/end(). This will avoid for example taking a DNA
in kvm_load_guest_fpu() when it tries to load the fpu immediately
after doing unlazy_fpu() on the host side.

More importantly this will prevent the host process fpu from being
corrupted.

Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
Link: http://lkml.kernel.org/r/1345842782-24175-4-git-send-email-suresh.b.siddha@intel.com
Cc: Avi Kivity <avi@...hat.com>
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
Cc: Rui Xiang <rui.xiang@...wei.com>
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 arch/x86/kvm/x86.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 318a245..55ee4ca 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5907,7 +5907,7 @@ void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
 	 */
 	kvm_put_guest_xcr0(vcpu);
 	vcpu->guest_fpu_loaded = 1;
-	unlazy_fpu(current);
+	kernel_fpu_begin();
 	fpu_restore_checking(&vcpu->arch.guest_fpu);
 	trace_kvm_fpu(1);
 }
@@ -5921,6 +5921,7 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
 
 	vcpu->guest_fpu_loaded = 0;
 	fpu_save_init(&vcpu->arch.guest_fpu);
+	kernel_fpu_end();
 	++vcpu->stat.fpu_reload;
 	kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
 	trace_kvm_fpu(0);
-- 
1.9.1

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