[PATCH 31/33] KVM: MMU: Flush guest tlb when reducing permissions on a pte

[Avi Kivity <avi@qumranet.com>]

If we reduce permissions on a pte, we must flush the cached copy of the pte
from the guest's tlb.

This is implemented at the moment by flushing the entire guest tlb, and can
be improved by flushing just the relevant virtual address, if it is known.

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

Index: linux-2.6/drivers/kvm/mmu.c
===================================================================
--- linux-2.6.orig/drivers/kvm/mmu.c
+++ linux-2.6/drivers/kvm/mmu.c
@@ -383,6 +383,7 @@ static void rmap_write_protect(struct kv
 		BUG_ON(!(*spte & PT_WRITABLE_MASK));
 		rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
 		rmap_remove(vcpu, spte);
+		kvm_arch_ops->tlb_flush(vcpu);
 		*spte &= ~(u64)PT_WRITABLE_MASK;
 	}
 }
@@ -594,6 +595,7 @@ static void kvm_mmu_page_unlink_children
 				rmap_remove(vcpu, &pt[i]);
 			pt[i] = 0;
 		}
+		kvm_arch_ops->tlb_flush(vcpu);
 		return;
 	}
 
@@ -927,7 +929,10 @@ static inline void set_pte_common(struct
 			pgprintk("%s: found shadow page for %lx, marking ro\n",
 				 __FUNCTION__, gfn);
 			access_bits &= ~PT_WRITABLE_MASK;
-			*shadow_pte &= ~PT_WRITABLE_MASK;
+			if (is_writeble_pte(*shadow_pte)) {
+				    *shadow_pte &= ~PT_WRITABLE_MASK;
+				    kvm_arch_ops->tlb_flush(vcpu);
+			}
 		}
 	}
 
-
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