From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: [PATCH v2 6/6] KVM: MMU: using __xchg_spte more smarter Date: Fri, 16 Jul 2010 11:30:18 +0800 Message-ID: <4C3FD24A.9020605@cn.fujitsu.com> References: <4C3FCFD7.5070005@cn.fujitsu.com> <4C3FD1C9.5010909@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM list To: Avi Kivity Return-path: In-Reply-To: <4C3FD1C9.5010909@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Sometimes, atomically set spte is not needed, this patch call __xchg_spte() more smartly Note: if the old mapping's access bit is already set, we no need atomic operation since the access bit is not lost Signed-off-by: Xiao Guangrong --- arch/x86/kvm/mmu.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index fb3ae54..71e9268 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -682,9 +682,14 @@ static void rmap_remove(struct kvm *kvm, u64 *spte) static void set_spte_track_bits(u64 *sptep, u64 new_spte) { pfn_t pfn; - u64 old_spte; + u64 old_spte = *sptep; + + if (!shadow_accessed_mask || !is_shadow_present_pte(old_spte) || + old_spte & shadow_accessed_mask) { + __set_spte(sptep, new_spte); + } else + old_spte = __xchg_spte(sptep, new_spte); - old_spte = __xchg_spte(sptep, new_spte); if (!is_rmap_spte(old_spte)) return; pfn = spte_to_pfn(old_spte); -- 1.6.1.2