KVM: MMU: Switch to mmu spinlock

Convert the synchronization of the shadow handling to a separate mmu_lock
spinlock.

Also guard fetch() by mmap_sem in read-mode to protect against alias
and memslot changes.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 3d7846ba26e1..a35b83a4fef2 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -387,7 +387,6 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
          */
         r = FNAME(walk_addr)(&walker, vcpu, addr, write_fault, user_fault,
                              fetch_fault);
-        up_read(&current->mm->mmap_sem);
 
         /*
          * The page is not mapped by the guest.  Let the guest handle it.
@@ -396,12 +395,13 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
                 pgprintk("%s: guest page fault\n", __FUNCTION__);
                 inject_page_fault(vcpu, addr, walker.error_code);
                 vcpu->arch.last_pt_write_count = 0; /* reset fork detector */
+                up_read(&current->mm->mmap_sem);
                 return 0;
         }
 
         page = gfn_to_page(vcpu->kvm, walker.gfn);
 
-        mutex_lock(&vcpu->kvm->lock);
+        spin_lock(&vcpu->kvm->mmu_lock);
         shadow_pte = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault,
                                   &write_pt, page);
         pgprintk("%s: shadow pte %p %llx ptwrite %d\n", __FUNCTION__,
@@ -414,13 +414,15 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
          * mmio: emulate if accessible, otherwise its a guest fault.
          */
         if (shadow_pte && is_io_pte(*shadow_pte)) {
-                mutex_unlock(&vcpu->kvm->lock);
+                spin_unlock(&vcpu->kvm->mmu_lock);
+                up_read(&current->mm->mmap_sem);
                 return 1;
         }
 
         ++vcpu->stat.pf_fixed;
         kvm_mmu_audit(vcpu, "post page fault (fixed)");
-        mutex_unlock(&vcpu->kvm->lock);
+        spin_unlock(&vcpu->kvm->mmu_lock);
+        up_read(&current->mm->mmap_sem);
 
         return write_pt;
 }