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authorTakuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>2013-03-12 17:45:30 +0900
committerGleb Natapov <gleb@redhat.com>2013-03-14 10:21:21 +0200
commit982b3394dd23eec6e5a2f7871238435a167b63cc (patch)
tree24e7cbbfdfa7500aa1e685b80aee205bf2ff17af /arch/x86/kvm/x86.c
parent95b0430d1a53541076ffbaf453f8b49a547cceba (diff)
KVM: x86: Optimize mmio spte zapping when creating/moving memslot
When we create or move a memory slot, we need to zap mmio sptes. Currently, zap_all() is used for this and this is causing two problems: - extra page faults after zapping mmu pages - long mmu_lock hold time during zapping mmu pages For the latter, Marcelo reported a disastrous mmu_lock hold time during hot-plug, which made the guest unresponsive for a long time. This patch takes a simple way to fix these problems: do not zap mmu pages unless they are marked mmio cached. On our test box, this took only 50us for the 4GB guest and we did not see ms of mmu_lock hold time any more. Note that we still need to do zap_all() for other cases. So another work is also needed: Xiao's work may be the one. Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp> Signed-off-by: Gleb Natapov <gleb@redhat.com>
Diffstat (limited to 'arch/x86/kvm/x86.c')
-rw-r--r--arch/x86/kvm/x86.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 61a5bb60af8..d3c478742e2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6991,7 +6991,7 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
* mmio sptes.
*/
if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {
- kvm_mmu_zap_all(kvm);
+ kvm_mmu_zap_mmio_sptes(kvm);
kvm_reload_remote_mmus(kvm);
}
}