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From: Junaid Shahid <junaids@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com>,
	kvm@vger.kernel.org, andreslc@google.com, pfeiner@google.com
Subject: Re: [PATCH v3 7/8] kvm: x86: mmu: Lockless access tracking for Intel CPUs without EPT A bits.
Date: Fri, 16 Dec 2016 16:01:02 -0800	[thread overview]
Message-ID: <1518872.OXBznDnly6@js-desktop.mtv.corp.google.com> (raw)
In-Reply-To: <736ae8e7-271a-d4d0-5535-5899f64d2b93@redhat.com>


On Friday, December 16, 2016 04:23:21 PM Paolo Bonzini wrote:
> Junaid, of all comments from Guangrong I'm mostly interested in
> kvm_mmu_clear_all_pte_masks.  What was the intended purpose?

This was needed in the original version of this patch where the shadow_acc_track_mask was set via the separate kvm_mmu_set_access_track_masks() call rather than as part of kvm_mmu_set_mask_ptes(). In that case, without the clearing during init, we could end up with both shadow_acc_track_mask and shadow_accessed_mask being set if the kvm_intel module was reloaded with different EPT parameters e.g.

modprobe kvm_intel ept_ad=0 
rmmod kvm_intel                 
modprobe kvm_intel ept_ad=1    

Now that we are setting both masks together through kvm_mmu_set_mask_ptes(), this problem doesn’t exist and the kvm_mmu_clear_all_pte_masks() isn’t strictly needed. However, I think it might still be a good idea to keep it because the basic issue is that these masks are expected to be set by the kvm_(intel|amd) modules but they are actually a part of the kvm module and hence they are initialized to 0 only on the (re)loading of the kvm module, but not of the kvm_(intel|amd) modules.

Thanks,
Junaid

  reply	other threads:[~2016-12-17  0:01 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
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 [this message]
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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