linux-kernel - [PATCH 31/31] KVM: MMU: kvm_pv_mmu_op should not take mmap

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Date:	Mon, 21 Apr 2008 13:29:57 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	kvm-devel@...ts.sourceforge.net
Cc:	linux-kernel@...r.kernel.org, Marcelo Tosatti <mtosatti@...hat.com>
Subject: [PATCH 31/31] KVM: MMU: kvm_pv_mmu_op should not take mmap_sem

From: Marcelo Tosatti <mtosatti@...hat.com>

kvm_pv_mmu_op should not take mmap_sem. All gfn_to_page() callers down
in the MMU processing will take it if necessary, so as it is it can
deadlock.

Apparently a leftover from the days before slots_lock.

Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Avi Kivity <avi@...ranet.com>
---
 arch/x86/kvm/mmu.c |    3 ---
 1 files changed, 0 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 078a7f1..2ad6f54 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2173,8 +2173,6 @@ int kvm_pv_mmu_op(struct kvm_vcpu *vcpu, unsigned long bytes,
 	int r;
 	struct kvm_pv_mmu_op_buffer buffer;
 
-	down_read(&current->mm->mmap_sem);
-
 	buffer.ptr = buffer.buf;
 	buffer.len = min_t(unsigned long, bytes, sizeof buffer.buf);
 	buffer.processed = 0;
@@ -2194,7 +2192,6 @@ int kvm_pv_mmu_op(struct kvm_vcpu *vcpu, unsigned long bytes,
 	r = 1;
 out:
 	*ret = buffer.processed;
-	up_read(&current->mm->mmap_sem);
 	return r;
 }
 
-- 
1.5.5

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