From: Hollis Blanchard <hollisb@us.ibm.com>
Date: Wed, 21 May 2008 23:22:54 +0000 (-0500)
Subject: KVM: ppc: Use a read lock around MMU operations, and release it on error
X-Git-Tag: v2.6.26-rc6~11^2~7
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=905fa4b9d6e2c9fd1c9ad84e3abe83021f498f53;p=linux-2.6

KVM: ppc: Use a read lock around MMU operations, and release it on error

gfn_to_page() and kvm_release_page_clean() are called from other contexts with
mmap_sem locked only for reading.

Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
---

diff --git a/arch/powerpc/kvm/44x_tlb.c b/arch/powerpc/kvm/44x_tlb.c
index aa649c7db9..1c48d6164b 100644
--- a/arch/powerpc/kvm/44x_tlb.c
+++ b/arch/powerpc/kvm/44x_tlb.c
@@ -142,18 +142,19 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn, u64 asid,
 	stlbe = &vcpu->arch.shadow_tlb[victim];
 
 	/* Get reference to new page. */
-	down_write(&current->mm->mmap_sem);
+	down_read(&current->mm->mmap_sem);
 	new_page = gfn_to_page(vcpu->kvm, gfn);
 	if (is_error_page(new_page)) {
 		printk(KERN_ERR "Couldn't get guest page!\n");
 		kvm_release_page_clean(new_page);
+		up_read(&current->mm->mmap_sem);
 		return;
 	}
 	hpaddr = page_to_phys(new_page);
 
 	/* Drop reference to old page. */
 	kvmppc_44x_shadow_release(vcpu, victim);
-	up_write(&current->mm->mmap_sem);
+	up_read(&current->mm->mmap_sem);
 
 	vcpu->arch.shadow_pages[victim] = new_page;