From: Paolo Bonzini <pbonzini@redhat.com>
To: Junaid Shahid <junaids@google.com>
Cc: kvm@vger.kernel.org, andreslc@google.com, pfeiner@google.com,
guangrong xiao <guangrong.xiao@linux.intel.com>
Subject: Re: [PATCH v2 4/5] kvm: x86: mmu: Lockless access tracking for Intel CPUs without EPT A bits.
Date: Fri, 2 Dec 2016 03:33:38 -0500 (EST) [thread overview]
Message-ID: <1327709090.1161444.1480667618524.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <56954113.ZmdEA1QfJc@js-desktop.mtv.corp.google.com>
> On Monday, November 21, 2016 03:42:23 PM Paolo Bonzini wrote:
> > Please rewrite kvm_age_rmapp to use the new mmu_spte_age instead
>
> Hi Paolo,
>
> While updating kvm_age_rmapp/mmu_spte_age, I noticed an inconsistency in the
> existing kvm code between the A/D and non-A/D cases. When using A/D bits,
> kvm_age_hva calls kvm_age_rmapp, which does NOT call kvm_set_pfn_accessed.
> However, when using EPT without A/D bits, kvm_unmap_rmapp is called, which
> does internally end up in a call to kvm_set_pfn_accessed. Do you know if
> this difference is deliberate? If not, should we call kvm_set_pfn_accessed
> in the A/D case as well, or should we leave that as is? Does it make any
> difference?
I think it's correct _not_ to call kvm_set_pfn_accessed, because the
clear_flush_young MMU notifier is called when you want to clear the
accessed bit. So your patch would be fixing a bug in the case where
EPT A/D bits aren't available.
Thanks,
Paolo
next prev parent reply other threads:[~2016-12-02 8:33 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-27 2:19 [PATCH 0/4] Lockless Access Tracking for Intel CPUs without EPT A bits Junaid Shahid
2016-10-27 2:19 ` [PATCH 1/4] kvm: x86: mmu: Use symbolic constants for EPT Violation Exit Qualifications Junaid Shahid
2016-11-02 18:03 ` Paolo Bonzini
2016-11-02 21:40 ` Junaid Shahid
2016-10-27 2:19 ` [PATCH 2/4] kvm: x86: mmu: Rename spte_is_locklessly_modifiable() Junaid Shahid
2016-10-27 2:19 ` [PATCH 3/4] kvm: x86: mmu: Fast Page Fault path retries Junaid Shahid
2016-10-27 2:19 ` [PATCH 4/4] kvm: x86: mmu: Lockless access tracking for Intel CPUs without EPT A bits Junaid Shahid
2016-11-02 18:01 ` Paolo Bonzini
2016-11-02 21:42 ` Junaid Shahid
2016-11-08 23:00 ` [PATCH v2 0/5] Lockless Access Tracking " Junaid Shahid
2016-11-08 23:00 ` [PATCH v2 1/5] kvm: x86: mmu: Use symbolic constants for EPT Violation Exit Qualifications Junaid Shahid
2016-11-21 13:06 ` Paolo Bonzini
2016-11-08 23:00 ` [PATCH v2 2/5] kvm: x86: mmu: Rename spte_is_locklessly_modifiable() Junaid Shahid
2016-11-21 13:07 ` Paolo Bonzini
2016-11-08 23:00 ` [PATCH v2 3/5] kvm: x86: mmu: Fast Page Fault path retries Junaid Shahid
2016-11-21 13:13 ` Paolo Bonzini
2016-11-08 23:00 ` [PATCH v2 4/5] kvm: x86: mmu: Lockless access tracking for Intel CPUs without EPT A bits Junaid Shahid
2016-11-21 14:42 ` Paolo Bonzini
2016-11-24 3:50 ` Junaid Shahid
2016-11-25 9:45 ` Paolo Bonzini
2016-11-29 2:43 ` Junaid Shahid
2016-11-29 8:09 ` Paolo Bonzini
2016-11-30 0:59 ` Junaid Shahid
2016-11-30 11:09 ` Paolo Bonzini
2016-12-01 22:54 ` Junaid Shahid
2016-12-02 8:33 ` Paolo Bonzini [this message]
2016-12-05 22:57 ` Junaid Shahid
2016-11-08 23:00 ` [PATCH v2 5/5] kvm: x86: mmu: Update documentation for fast page fault mechanism Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 0/8] Lockless Access Tracking for Intel CPUs without EPT A bits Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 1/8] kvm: x86: mmu: Use symbolic constants for EPT Violation Exit Qualifications Junaid Shahid
2016-12-15 6:50 ` Xiao Guangrong
2016-12-15 23:06 ` Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 2/8] kvm: x86: mmu: Rename spte_is_locklessly_modifiable() Junaid Shahid
2016-12-15 6:51 ` Xiao Guangrong
2016-12-07 0:46 ` [PATCH v3 3/8] kvm: x86: mmu: Fast Page Fault path retries Junaid Shahid
2016-12-15 7:20 ` Xiao Guangrong
2016-12-15 23:36 ` Junaid Shahid
2016-12-16 13:13 ` Xiao Guangrong
2016-12-17 0:36 ` Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 4/8] kvm: x86: mmu: Refactor accessed/dirty checks in mmu_spte_update/clear Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 5/8] kvm: x86: mmu: Introduce a no-tracking version of mmu_spte_update Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 6/8] kvm: x86: mmu: Do not use bit 63 for tracking special SPTEs Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 7/8] kvm: x86: mmu: Lockless access tracking for Intel CPUs without EPT A bits Junaid Shahid
2016-12-14 16:28 ` Paolo Bonzini
2016-12-14 22:36 ` Junaid Shahid
2016-12-14 23:35 ` Paolo Bonzini
2016-12-16 13:04 ` Xiao Guangrong
2016-12-16 15:23 ` Paolo Bonzini
2016-12-17 0:01 ` Junaid Shahid
2016-12-21 9:49 ` Xiao Guangrong
2016-12-21 18:00 ` Paolo Bonzini
2016-12-17 2:04 ` Junaid Shahid
2016-12-17 14:19 ` Paolo Bonzini
2016-12-20 3:36 ` Junaid Shahid
2016-12-20 9:01 ` Paolo Bonzini
2016-12-07 0:46 ` [PATCH v3 8/8] kvm: x86: mmu: Update documentation for fast page fault mechanism Junaid Shahid
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