[PATCH 10/19] KVM: mmu_shrink: kvm_mmu_zap_page requires slots_lock to be held

[Avi Kivity]

From: Marcelo Tosatti <[EMAIL PROTECTED]>

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 <[EMAIL PROTECTED]>
---
 arch/x86/kvm/mmu.c |3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 1fd8e3b..ff7cf63 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);
-- 
1.5.6.1

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Re: KVM: mmu_shrink: kvm_mmu_zap_page requires slots_lock to be held

[Avi Kivity]

Marcelo Tosatti wrote:

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().
  


Applied, thanks.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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KVM: mmu_shrink: kvm_mmu_zap_page requires slots_lock to be held

[Marcelo Tosatti]

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.

Index: kvm/arch/x86/kvm/mmu.c
===
--- kvm.orig/arch/x86/kvm/mmu.c
+++ kvm/arch/x86/kvm/mmu.c
@@ -1987,6 +1987,8 @@ static int mmu_shrink(int nr_to_scan, gf
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, gf
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);
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