From: guangrong.xiao@gmail.com To: pbonzini@redhat.com, mtosatti@redhat.com, avi.kivity@gmail.com, rkrcmar@redhat.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, Xiao Guangrong <xiaoguangrong@tencent.com> Subject: [PATCH v2 6/7] KVM: MMU: clarify fast_pf_fix_direct_spte Date: Tue, 20 Jun 2017 17:15:25 +0800 [thread overview] Message-ID: <20170620091526.4287-7-xiaoguangrong@tencent.com> (raw) In-Reply-To: <20170620091526.4287-1-xiaoguangrong@tencent.com> From: Xiao Guangrong <xiaoguangrong@tencent.com> The writable spte can not be locklessly fixed and add a WARN_ON() to trigger the warning if something out of our mind happens, that is good for us to track if the log for writable spte is missed on the fast path Signed-off-by: Xiao Guangrong <xiaoguangrong@tencent.com> --- arch/x86/kvm/mmu.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index c011ab0..7711953 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3240,6 +3240,15 @@ fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, WARN_ON(!sp->role.direct); /* + * the original spte can not be writable as only the spte which + * fulfills is_access_track_spte() or + * spte_can_locklessly_be_made_writable() can be locklessly fixed, + * for the former, the W bit is always cleared, for the latter, + * there is nothing to do if it is already writable. + */ + WARN_ON(is_writable_pte(old_spte)); + + /* * Theoretically we could also set dirty bit (and flush TLB) here in * order to eliminate unnecessary PML logging. See comments in * set_spte. But fast_page_fault is very unlikely to happen with PML @@ -3254,7 +3263,7 @@ fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, if (cmpxchg64(sptep, old_spte, new_spte) != old_spte) return false; - if (is_writable_pte(new_spte) && !is_writable_pte(old_spte)) { + if (is_writable_pte(new_spte)) { /* * The gfn of direct spte is stable since it is * calculated by sp->gfn. -- 2.9.4
WARNING: multiple messages have this Message-ID (diff)
From: guangrong.xiao@gmail.com To: pbonzini@redhat.com, mtosatti@redhat.com, avi.kivity@gmail.com, rkrcmar@redhat.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, Xiao Guangrong <xiaoguangrong@tencent.com> Subject: [Qemu-devel] [PATCH v2 6/7] KVM: MMU: clarify fast_pf_fix_direct_spte Date: Tue, 20 Jun 2017 17:15:25 +0800 [thread overview] Message-ID: <20170620091526.4287-7-xiaoguangrong@tencent.com> (raw) In-Reply-To: <20170620091526.4287-1-xiaoguangrong@tencent.com> From: Xiao Guangrong <xiaoguangrong@tencent.com> The writable spte can not be locklessly fixed and add a WARN_ON() to trigger the warning if something out of our mind happens, that is good for us to track if the log for writable spte is missed on the fast path Signed-off-by: Xiao Guangrong <xiaoguangrong@tencent.com> --- arch/x86/kvm/mmu.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index c011ab0..7711953 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3240,6 +3240,15 @@ fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, WARN_ON(!sp->role.direct); /* + * the original spte can not be writable as only the spte which + * fulfills is_access_track_spte() or + * spte_can_locklessly_be_made_writable() can be locklessly fixed, + * for the former, the W bit is always cleared, for the latter, + * there is nothing to do if it is already writable. + */ + WARN_ON(is_writable_pte(old_spte)); + + /* * Theoretically we could also set dirty bit (and flush TLB) here in * order to eliminate unnecessary PML logging. See comments in * set_spte. But fast_page_fault is very unlikely to happen with PML @@ -3254,7 +3263,7 @@ fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, if (cmpxchg64(sptep, old_spte, new_spte) != old_spte) return false; - if (is_writable_pte(new_spte) && !is_writable_pte(old_spte)) { + if (is_writable_pte(new_spte)) { /* * The gfn of direct spte is stable since it is * calculated by sp->gfn. -- 2.9.4
next prev parent reply other threads:[~2017-06-20 9:16 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-06-20 9:15 [PATCH v2 0/7] KVM: MMU: fast write protect guangrong.xiao 2017-06-20 9:15 ` [Qemu-devel] " guangrong.xiao 2017-06-20 9:15 ` [PATCH v2 1/7] KVM: MMU: correct the behavior of mmu_spte_update_no_track guangrong.xiao 2017-06-20 9:15 ` [Qemu-devel] " guangrong.xiao 2017-06-20 9:15 ` [PATCH v2 2/7] KVM: MMU: introduce possible_writable_spte_bitmap guangrong.xiao 2017-06-20 9:15 ` [Qemu-devel] " guangrong.xiao 2017-06-20 9:15 ` [PATCH v2 3/7] KVM: MMU: introduce kvm_mmu_write_protect_all_pages guangrong.xiao 2017-06-20 9:15 ` [Qemu-devel] " guangrong.xiao 2017-06-20 9:15 ` [PATCH v2 4/7] KVM: MMU: enable KVM_WRITE_PROTECT_ALL_MEM guangrong.xiao 2017-06-20 9:15 ` [Qemu-devel] " guangrong.xiao 2017-06-20 9:15 ` [PATCH v2 5/7] KVM: MMU: allow dirty log without write protect guangrong.xiao 2017-06-20 9:15 ` [Qemu-devel] " guangrong.xiao 2017-06-20 9:15 ` guangrong.xiao [this message] 2017-06-20 9:15 ` [Qemu-devel] [PATCH v2 6/7] KVM: MMU: clarify fast_pf_fix_direct_spte guangrong.xiao 2017-06-20 9:15 ` [PATCH v2 7/7] KVM: MMU: stop using mmu_spte_get_lockless under mmu-lock guangrong.xiao 2017-06-20 9:15 ` [Qemu-devel] " guangrong.xiao 2017-07-03 14:39 ` [PATCH v2 0/7] KVM: MMU: fast write protect Xiao Guangrong 2017-07-03 14:39 ` [Qemu-devel] " Xiao Guangrong 2017-07-03 15:47 ` Paolo Bonzini 2017-07-03 15:47 ` [Qemu-devel] " Paolo Bonzini 2017-07-04 3:17 ` Xiao Guangrong 2017-07-04 3:17 ` [Qemu-devel] " Xiao Guangrong
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