[1/3] KVM: x86: remove unnecessary rmap walk of read-only memslots
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Message ID 1591128450-11977-2-git-send-email-anthony.yznaga@oracle.com
State New
Headers show
Series
  • avoid unnecessary memslot rmap walks
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Commit Message

Anthony Yznaga June 2, 2020, 8:07 p.m. UTC
There's no write access to remove.  An existing memslot cannot be updated
to set or clear KVM_MEM_READONLY, and any mappings established in a newly
created or moved read-only memslot will already be read-only.

Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
---
 arch/x86/kvm/x86.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

Patch
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diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c17e6eb9ad43..23fd888e52ee 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10038,11 +10038,9 @@  int kvm_arch_prepare_memory_region(struct kvm *kvm,
 static void kvm_mmu_slot_apply_flags(struct kvm *kvm,
 				     struct kvm_memory_slot *new)
 {
-	/* Still write protect RO slot */
-	if (new->flags & KVM_MEM_READONLY) {
-		kvm_mmu_slot_remove_write_access(kvm, new, PT_PAGE_TABLE_LEVEL);
+	/* Nothing to do for RO slots */
+	if (new->flags & KVM_MEM_READONLY)
 		return;
-	}
 
 	/*
 	 * Call kvm_x86_ops dirty logging hooks when they are valid.