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From: Paolo Bonzini <>
To: Maxim Levitsky <>,
Cc: Jim Mattson <>,, Wanpeng Li <>,
	Borislav Petkov <>, Joerg Roedel <>,
	Suravee Suthikulpanit <>,
	"H. Peter Anvin" <>,
	Thomas Gleixner <>,
	Ingo Molnar <>,
	Vitaly Kuznetsov <>,
	Sean Christopherson <>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
Subject: Re: [PATCH v4 00/16] My AVIC patch queue
Date: Wed, 11 Aug 2021 10:06:43 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 10/08/21 23:21, Maxim Levitsky wrote:
> On Tue, 2021-08-10 at 23:52 +0300, Maxim Levitsky wrote:
>> Hi!
>> This is a series of bugfixes to the AVIC dynamic inhibition, which was
>> made while trying to fix bugs as much as possible in this area and trying
>> to make the AVIC+SYNIC conditional enablement work.
>> * Patches 1,3-8 are code from Sean Christopherson which
> I mean patches 1,4-8. I forgot about patch 3 which I also added,
> which just added a comment about parameters of the kvm_flush_remote_tlbs_with_address.
> Best regards,
> 	Maxim Levitsky
>>    implement an alternative approach of inhibiting AVIC without
>>    disabling its memslot.
>>    V4: addressed review feedback.
>> * Patch 2 is new and it fixes a bug in kvm_flush_remote_tlbs_with_address
>> * Patches 9-10 in this series fix a race condition which can cause
>>    a lost write from a guest to APIC when the APIC write races
>>    the AVIC un-inhibition, and add a warning to catch this problem
>>    if it re-emerges again.
>>    V4: applied review feedback from Paolo
>> * Patch 11 is the patch from Vitaly about allowing AVIC with SYNC
>>    as long as the guest doesn’t use the AutoEOI feature. I only slightly
>>    changed it to expose the AutoEOI cpuid bit regardless of AVIC enablement.
>>    V4: fixed a race that Paolo pointed out.
>> * Patch 12 is a refactoring that is now possible in SVM AVIC inhibition code,
>>    because the RCU lock is not dropped anymore.
>> * Patch 13-15 fixes another issue I found in AVIC inhibit code:
>>    Currently avic_vcpu_load/avic_vcpu_put are called on userspace entry/exit
>>    from KVM (aka kvm_vcpu_get/kvm_vcpu_put), and these functions update the
>>    "is running" bit in the AVIC physical ID remap table and update the
>>    target vCPU in iommu code.
>>    However both of these functions don't do anything when AVIC is inhibited
>>    thus the "is running" bit will be kept enabled during the exit to userspace.
>>    This shouldn't be a big issue as the caller
>>    doesn't use the AVIC when inhibited but still inconsistent and can trigger
>>    a warning about this in avic_vcpu_load.
>>    To be on the safe side I think it makes sense to call
>>    avic_vcpu_put/avic_vcpu_load when inhibiting/uninhibiting the AVIC.
>>    This will ensure that the work these functions do is matched.
>>    V4: I splitted a single patch to 3 patches to make it easier
>>        to review, and applied Paolo's review feedback.
>> * Patch 16 removes the pointless APIC base
>>    relocation from AVIC to make it consistent with the rest of KVM.
>>    (both AVIC and APICv only support default base, while regular KVM,
>>    sort of support any APIC base as long as it is not RAM.
>>    If guest attempts to relocate APIC base to non RAM area,
>>    while APICv/AVIC are active, the new base will be non accelerated,
>>    while the default base will continue to be AVIC/APICv backed).
>>    On top of that if guest uses different APIC bases on different vCPUs,
>>    KVM doesn't honour the fact that the MMIO range should only be active
>>    on that vCPU.

No problem, b4 diff is my friend. :)  Queued, thanks.


      reply	other threads:[~2021-08-11  8:08 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-10 20:52 Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 01/16] Revert "KVM: x86/mmu: Allow zap gfn range to operate under the mmu read lock" Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 02/16] KVM: x86/mmu: fix parameters to kvm_flush_remote_tlbs_with_address Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 03/16] KVM: x86/mmu: add comment explaining arguments to kvm_zap_gfn_range Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 04/16] KVM: x86/mmu: bump mmu notifier count in kvm_zap_gfn_range Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 05/16] KVM: x86/mmu: rename try_async_pf to kvm_faultin_pfn Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 06/16] KVM: x86/mmu: allow kvm_faultin_pfn to return page fault handling code Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 07/16] KVM: x86/mmu: allow APICv memslot to be enabled but invisible Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 08/16] KVM: x86: don't disable APICv memslot when inhibited Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 09/16] KVM: x86: APICv: fix race in kvm_request_apicv_update on SVM Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 10/16] KVM: SVM: add warning for mistmatch between AVIC vcpu state and AVIC inhibition Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 11/16] KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in use Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 12/16] KVM: SVM: remove svm_toggle_avic_for_irq_window Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 13/16] KVM: SVM: avoid refreshing avic if its state didn't change Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 14/16] KVM: SVM: move check for kvm_vcpu_apicv_active outside of avic_vcpu_{put|load} Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 15/16] KVM: SVM: call avic_vcpu_load/avic_vcpu_put when enabling/disabling AVIC Maxim Levitsky
2021-08-10 20:52 ` [PATCH v4 16/16] KVM: SVM: AVIC: drop unsupported AVIC base relocation code Maxim Levitsky
2021-08-10 21:21 ` [PATCH v4 00/16] My AVIC patch queue Maxim Levitsky
2021-08-11  8:06   ` Paolo Bonzini [this message]

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