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From: Paolo Bonzini <pbonzini@redhat.com>
To: Maxim Levitsky <mlevitsk@redhat.com>, kvm@vger.kernel.org
Cc: Wanpeng Li <wanpengli@tencent.com>,
Thomas Gleixner <tglx@linutronix.de>,
Joerg Roedel <joro@8bytes.org>, Borislav Petkov <bp@alien8.de>,
Sean Christopherson <seanjc@google.com>,
Jim Mattson <jmattson@google.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>,
"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<linux-kernel@vger.kernel.org>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v3 05/12] KVM: x86/mmu: allow APICv memslot to be partially enabled
Date: Tue, 3 Aug 2021 11:12:33 +0200 [thread overview]
Message-ID: <596639a1-4df3-54e7-3f72-1bd292e592a2@redhat.com> (raw)
In-Reply-To: <20210802183329.2309921-6-mlevitsk@redhat.com>
On 02/08/21 20:33, Maxim Levitsky wrote:
> on AMD, APIC virtualization needs to dynamicaly inhibit the AVIC in a
> response to some events, and this is problematic and not efficient to do by
> enabling/disabling the memslot that covers APIC's mmio range.
> Plus due to SRCU locking, it makes it more complex to request AVIC inhibition.
>
> Instead, the APIC memslot will be always enabled, but the MMU code
> will not install a SPTE for it, when arch.apic_access_memslot_enabled == false
> and instead jump straight to emulating the access.
>
> When inhibiting the AVIC, this SPTE will be zapped.
>
> This code is based on a suggestion from Sean Christopherson:
> https://lkml.org/lkml/2021/7/19/2970
>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
> arch/x86/kvm/mmu/mmu.c | 23 ++++++++++++++++++-----
> 1 file changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 6f77f6efd43c..965b562da893 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3857,11 +3857,24 @@ static bool kvm_faultin_pfn(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
> if (slot && (slot->flags & KVM_MEMSLOT_INVALID))
> goto out_retry;
>
> - /* Don't expose private memslots to L2. */
> - if (is_guest_mode(vcpu) && !kvm_is_visible_memslot(slot)) {
> - *pfn = KVM_PFN_NOSLOT;
> - *writable = false;
> - return false;
> + if (!kvm_is_visible_memslot(slot)) {
> + /* Don't expose private memslots to L2. */
> + if (is_guest_mode(vcpu)) {
> + *pfn = KVM_PFN_NOSLOT;
> + *writable = false;
> + return false;
> + }
> + /*
> + * If the APIC access page exists but is disabled, go directly
> + * to emulation without caching the MMIO access or creating a
> + * MMIO SPTE. That way the cache doesn't need to be purged
> + * when the AVIC is re-enabled.
> + */
> + if (slot && slot->id == APIC_ACCESS_PAGE_PRIVATE_MEMSLOT &&
> + !vcpu->kvm->arch.apic_access_memslot_enabled) {
In addition to using apicv_inhibit_reasons, I would change the subject
to "allow APICv memslot to be enabled but invisible". Otherwise looks good.
Paolo
> + *r = RET_PF_EMULATE;
> + return true;
> + }
> }
>
> async = false;
>
next prev parent reply other threads:[~2021-08-03 9:12 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-02 18:33 [PATCH v3 00/12] My AVIC patch queue Maxim Levitsky
2021-08-02 18:33 ` [PATCH v3 01/12] Revert "KVM: x86/mmu: Allow zap gfn range to operate under the mmu read lock" Maxim Levitsky
2021-08-03 8:05 ` Paolo Bonzini
2021-08-03 15:11 ` Sean Christopherson
2021-08-03 17:29 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 02/12] KVM: x86/mmu: bump mmu notifier count in kvm_zap_gfn_range Maxim Levitsky
2021-08-03 9:00 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 03/12] KVM: x86/mmu: rename try_async_pf to kvm_faultin_pfn Maxim Levitsky
2021-08-03 9:00 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 04/12] KVM: x86/mmu: allow kvm_faultin_pfn to return page fault handling code Maxim Levitsky
2021-08-03 9:00 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 05/12] KVM: x86/mmu: allow APICv memslot to be partially enabled Maxim Levitsky
2021-08-03 9:12 ` Paolo Bonzini [this message]
2021-08-02 18:33 ` [PATCH v3 06/12] KVM: x86: don't disable APICv memslot when inhibited Maxim Levitsky
2021-08-03 8:44 ` Paolo Bonzini
2021-08-09 18:51 ` Maxim Levitsky
2021-08-09 19:14 ` Sean Christopherson
2021-08-02 18:33 ` [PATCH v3 07/12] KVM: x86: APICv: fix race in kvm_request_apicv_update on SVM Maxim Levitsky
2021-08-02 18:33 ` [PATCH v3 08/12] KVM: SVM: add warning for mistmatch between AVIC state and AVIC access page state Maxim Levitsky
2021-08-03 8:45 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 09/12] KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in use Maxim Levitsky
2021-08-03 8:47 ` Paolo Bonzini
2021-08-03 9:01 ` Paolo Bonzini
2021-08-03 9:11 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 10/12] KVM: SVM: remove svm_toggle_avic_for_irq_window Maxim Levitsky
2021-08-03 9:11 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 11/12] KVM: SVM: call avic_vcpu_load/avic_vcpu_put when enabling/disabling AVIC Maxim Levitsky
2021-08-03 9:00 ` Paolo Bonzini
2021-08-02 18:33 ` [PATCH v3 12/12] KVM: SVM: AVIC: drop unsupported AVIC base relocation code Maxim Levitsky
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