Re: [PATCH] KVM: MMU: Don't read pdptrs with mmu spinlock held in mmu_alloc_roots

2010-05-10 Thread Avi Kivity 

On 05/06/2010 10:10 PM, Marcelo Tosatti wrote:

On Tue, May 04, 2010 at 01:03:50PM +0300, Avi Kivity wrote:
   

On svm, kvm_read_pdptr() may require reading guest memory, which can sleep.

Push the spinlock into mmu_alloc_roots(), and only take it after we've read
the pdptr.

Marcelo, dropping and re-acquiring the lock before mmu_sync_roots(), is fine,
yes?
 

Yes, but you should call kvm_mmu_free_some_pages after reacquiring the
spin_lock, to guarantee kvm_mmu_alloc_page won't fail.

   


We never fail due to lack of free pages (but I agree it's cleaner).

The patch is already in, I'll send an incremental.

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error compiling committee.c: too many arguments to function

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Re: [PATCH] KVM: MMU: Don't read pdptrs with mmu spinlock held in mmu_alloc_roots

2010-05-04 Thread Roedel, Joerg 
On Tue, May 04, 2010 at 06:03:50AM -0400, Avi Kivity wrote:
 On svm, kvm_read_pdptr() may require reading guest memory, which can sleep.
 
 Push the spinlock into mmu_alloc_roots(), and only take it after we've read
 the pdptr.

This fixes the lockdep issue for me. Thanks.

Tested-by: Joerg Roedel joerg.roe...@amd.com

 
 Signed-off-by: Avi Kivity a...@redhat.com
 ---
 
 Marcelo, dropping and re-acquiring the lock before mmu_sync_roots(), is fine,
 yes?
 
  arch/x86/kvm/mmu.c |7 +++
  1 files changed, 7 insertions(+), 0 deletions(-)
 
 diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
 index 51eb6d6..de99638 100644
 --- a/arch/x86/kvm/mmu.c
 +++ b/arch/x86/kvm/mmu.c
 @@ -2065,11 +2065,13 @@ static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
   direct = 1;
   root_gfn = 0;
   }
 + spin_lock(vcpu-kvm-mmu_lock);
   sp = kvm_mmu_get_page(vcpu, root_gfn, 0,
 PT64_ROOT_LEVEL, direct,
 ACC_ALL, NULL);
   root = __pa(sp-spt);
   ++sp-root_count;
 + spin_unlock(vcpu-kvm-mmu_lock);
   vcpu-arch.mmu.root_hpa = root;
   return 0;
   }
 @@ -2093,11 +2095,14 @@ static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
   direct = 1;
   root_gfn = i  30;
   }
 + spin_lock(vcpu-kvm-mmu_lock);
   sp = kvm_mmu_get_page(vcpu, root_gfn, i  30,
 PT32_ROOT_LEVEL, direct,
 ACC_ALL, NULL);
   root = __pa(sp-spt);
   ++sp-root_count;
 + spin_unlock(vcpu-kvm-mmu_lock);
 +
   vcpu-arch.mmu.pae_root[i] = root | PT_PRESENT_MASK;
   }
   vcpu-arch.mmu.root_hpa = __pa(vcpu-arch.mmu.pae_root);
 @@ -2466,7 +2471,9 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
   goto out;
   spin_lock(vcpu-kvm-mmu_lock);
   kvm_mmu_free_some_pages(vcpu);
 + spin_unlock(vcpu-kvm-mmu_lock);
   r = mmu_alloc_roots(vcpu);
 + spin_lock(vcpu-kvm-mmu_lock);
   mmu_sync_roots(vcpu);
   spin_unlock(vcpu-kvm-mmu_lock);
   if (r)

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