From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Thu, 3 Jul 2008 21:33:02 +0000 (-0300)
Subject: KVM: mmu_shrink: kvm_mmu_zap_page requires slots_lock to be held
X-Git-Tag: v2.6.27-rc1~968^2~10
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=5a4c92880493945678315a6df810f7a21f55b985;p=linux-2.6-omap-h63xx.git

KVM: mmu_shrink: kvm_mmu_zap_page requires slots_lock to be held

kvm_mmu_zap_page() needs slots lock held (rmap_remove->gfn_to_memslot,
for example).

Since kvm_lock spinlock is held in mmu_shrink(), do a non-blocking
down_read_trylock().

Untested.

Signed-off-by: Avi Kivity <avi@qumranet.com>
---

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 1fd8e3b58cc..ff7cf632175 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1987,6 +1987,8 @@ static int mmu_shrink(int nr_to_scan, gfp_t gfp_mask)
 	list_for_each_entry(kvm, &vm_list, vm_list) {
 		int npages;
 
+		if (!down_read_trylock(&kvm->slots_lock))
+			continue;
 		spin_lock(&kvm->mmu_lock);
 		npages = kvm->arch.n_alloc_mmu_pages -
 			 kvm->arch.n_free_mmu_pages;
@@ -1999,6 +2001,7 @@ static int mmu_shrink(int nr_to_scan, gfp_t gfp_mask)
 		nr_to_scan--;
 
 		spin_unlock(&kvm->mmu_lock);
+		up_read(&kvm->slots_lock);
 	}
 	if (kvm_freed)
 		list_move_tail(&kvm_freed->vm_list, &vm_list);