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From: Sean Christopherson <seanjc@google.com>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ben Gardon <bgardon@google.com>,
	Makarand Sonare <makarandsonare@google.com>
Subject: Re: [PATCH 05/14] KVM: x86/mmu: Consult max mapping level when zapping collapsible SPTEs
Date: Thu, 18 Feb 2021 17:31:24 -0800	[thread overview]
Message-ID: <YC8U7IagCOfzeBpW@google.com> (raw)
In-Reply-To: <df6eb767-0ae0-84a3-3f05-1ece4cb9ce22@oracle.com>

On Thu, Feb 18, 2021, Mike Kravetz wrote:
> On 2/18/21 8:23 AM, Sean Christopherson wrote:
> > On Thu, Feb 18, 2021, Paolo Bonzini wrote:
> >> On 13/02/21 01:50, Sean Christopherson wrote:
> >>>
> >>>  		pfn = spte_to_pfn(iter.old_spte);
> >>>  		if (kvm_is_reserved_pfn(pfn) ||
> >>> -		    (!PageTransCompoundMap(pfn_to_page(pfn)) &&
> >>> -		     !kvm_is_zone_device_pfn(pfn)))
> >>> +		    iter.level >= kvm_mmu_max_mapping_level(kvm, slot, iter.gfn,
> >>> +							    pfn, PG_LEVEL_NUM))
> >>>  			continue;
> >>
> >>
> >> This changes the test to PageCompound.  Is it worth moving the change to
> >> patch 1?
> > 
> > Yes?  I originally did that in a separate patch, then changed my mind.
> > 
> > If PageTransCompoundMap() also detects HugeTLB pages, then it is the "better"
> > option as it checks that the page is actually mapped huge.  I dropped the change
> > because PageTransCompound() is just a wrapper around PageCompound(), and so I
> > assumed PageTransCompoundMap() would detect HugeTLB pages, too.  I'm not so sure
> > about that after rereading the code, yet again.
> 
> I have not followed this thread, but HugeTLB hit my mail filter and I can
> help with this question.
> 
> No, PageTransCompoundMap() will not detect HugeTLB.  hugetlb pages do not
> use the compound_mapcount_ptr field.  So, that final check/return in
> PageTransCompoundMap() will always be false.

Thanks Mike!

Paolo, I agree it makes sense to switch to PageCompound in the earlier patch, in
case this one needs to be reverted.

  reply	other threads:[~2021-02-19  1:32 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-13  0:50 [PATCH 00/14] KVM: x86/mmu: Dirty logging fixes and improvements Sean Christopherson
2021-02-13  0:50 ` [PATCH 01/14] KVM: x86/mmu: Expand collapsible SPTE zap for TDP MMU to ZONE_DEVICE pages Sean Christopherson
2021-02-18 12:36   ` Paolo Bonzini
2021-02-13  0:50 ` [PATCH 02/14] KVM: x86/mmu: Don't unnecessarily write-protect small pages in TDP MMU Sean Christopherson
2021-02-13  0:50 ` [PATCH 03/14] KVM: x86/mmu: Split out max mapping level calculation to helper Sean Christopherson
2021-02-13  0:50 ` [PATCH 04/14] KVM: x86/mmu: Pass the memslot to the rmap callbacks Sean Christopherson
2021-02-13  0:50 ` [PATCH 05/14] KVM: x86/mmu: Consult max mapping level when zapping collapsible SPTEs Sean Christopherson
2021-02-18 12:43   ` Paolo Bonzini
2021-02-18 16:23     ` Sean Christopherson
2021-02-18 22:30       ` Mike Kravetz
2021-02-19  1:31         ` Sean Christopherson [this message]
2021-02-13  0:50 ` [PATCH 06/14] KVM: nVMX: Disable PML in hardware when running L2 Sean Christopherson
2021-02-13  0:50 ` [PATCH 07/14] KVM: x86/mmu: Expand on the comment in kvm_vcpu_ad_need_write_protect() Sean Christopherson
2021-02-13  0:50 ` [PATCH 08/14] KVM: x86/mmu: Make dirty log size hook (PML) a value, not a function Sean Christopherson
2021-02-18 12:45   ` Paolo Bonzini
2021-02-13  0:50 ` [PATCH 09/14] KVM: x86: Move MMU's PML logic to common code Sean Christopherson
2021-02-13  0:50 ` [PATCH 10/14] KVM: x86: Further clarify the logic and comments for toggling log dirty Sean Christopherson
2021-02-18 12:50   ` Paolo Bonzini
2021-02-18 16:15     ` Sean Christopherson
2021-02-18 16:56       ` Paolo Bonzini
2021-02-13  0:50 ` [PATCH 11/14] KVM: VMX: Dynamically enable/disable PML based on memslot dirty logging Sean Christopherson
2021-02-13  0:50 ` [PATCH 12/14] KVM: x86/mmu: Don't set dirty bits when disabling dirty logging w/ PML Sean Christopherson
2021-02-18 17:08   ` Paolo Bonzini
2021-02-13  0:50 ` [PATCH 13/14] KVM: x86: Fold "write-protect large" use case into generic write-protect Sean Christopherson
2021-02-13  0:50 ` [PATCH 14/14] KVM: x86/mmu: Remove a variety of unnecessary exports Sean Christopherson
2021-02-17 22:50 ` [PATCH 00/14] KVM: x86/mmu: Dirty logging fixes and improvements Sean Christopherson
2021-02-18 12:57 ` Paolo Bonzini

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