linux-kernel - [patch] kvm: fix GFP_KERNEL allocation in atomic section in kvm_dev_ioctl_create

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Message-ID: <20061228124224.GA28573@elte.hu>
Date:	Thu, 28 Dec 2006 13:42:24 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Avi Kivity <avi@...ranet.com>
Cc:	kvm-devel <kvm-devel@...ts.sourceforge.net>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>,
	Linus Torvalds <torvalds@...l.org>
Subject: [patch] kvm: fix GFP_KERNEL allocation in atomic section in kvm_dev_ioctl_create_vcpu()

Subject: [patch] kvm: fix GFP_KERNEL allocation in atomic section in kvm_dev_ioctl_create_vcpu()
From: Ingo Molnar <mingo@...e.hu>

fix a GFP_KERNEL allocation in atomic section bug: 
kvm_dev_ioctl_create_vcpu() called kvm_mmu_init(), which calls 
alloc_pages(), while holding the vcpu. The fix is to set up the MMU 
state earlier, it does not require a loaded CPU state.

(NOTE: free_vcpus does an kvm_mmu_destroy() call so there's no need
 for any extra teardown branch on allocation failure here.)

found in 2.6.20-rc2-rt1.

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 drivers/kvm/kvm_main.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Index: linux/drivers/kvm/kvm_main.c
===================================================================
--- linux.orig/drivers/kvm/kvm_main.c
+++ linux/drivers/kvm/kvm_main.c
@@ -522,12 +522,12 @@ static int kvm_dev_ioctl_create_vcpu(str
 	if (r < 0)
 		goto out_free_vcpus;
 
-	kvm_arch_ops->vcpu_load(vcpu);
+	r = kvm_mmu_init(vcpu);
+	if (r < 0)
+		goto out_free_vcpus;
 
+	kvm_arch_ops->vcpu_load(vcpu);
 	r = kvm_arch_ops->vcpu_setup(vcpu);
-	if (r >= 0)
-		r = kvm_mmu_init(vcpu);
-
 	vcpu_put(vcpu);
 
 	if (r < 0)
-
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