From: Sean Christopherson <seanjc@google.com>
To: Maxim Levitsky <mlevitsk@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Alejandro Jimenez <alejandro.j.jimenez@oracle.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Li RongQing <lirongqing@baidu.com>
Subject: Re: [PATCH v4 11/32] KVM: x86: Inhibit APIC memslot if x2APIC and AVIC are enabled
Date: Fri, 16 Dec 2022 19:40:29 +0000 [thread overview]
Message-ID: <Y5zJraa0ddooauXB@google.com> (raw)
In-Reply-To: <Y5zBH+2VuPJi4yYV@google.com>
On Fri, Dec 16, 2022, Sean Christopherson wrote:
> On Thu, Dec 08, 2022, Maxim Levitsky wrote:
> > I prefer to just have a boolean 'is_avic' or,
> > '.needs_x2apic_memslot_inhibition' in the vendor ops, and check it in
> > 'kvm_vcpu_update_apicv' with the above comment on top of it.
> >
> > need_x2apic_memslot_inhibition can even be set to false when x2avic is
> > supported at the initalization time, because then AVIC behaves just like
> > APICv (when x2avic bit is enabled, AVIC mmio is no longer decoded).
>
> Oh, so SVM does effectively have independent controls, it's only the "hybrid" mode
> that's affected? In that case, how about this?
>
> /*
> * Due to sharing page tables across vCPUs, the xAPIC memslot must be
> * deleted if any vCPU has x2APIC enabled and hardware doesn't support
> * x2APIC virtualization. E.g. some AMD CPUs support AVIC but not
> * x2AVIC. KVM still allows enabling AVIC in this case so that KVM can
> * the AVIC doorbell to inject interrupts to running vCPUs, but KVM
> * mustn't create SPTEs for the APIC base as the vCPU would incorrectly
> * be able to access the vAPIC page via MMIO despite being in x2APIC
> * mode. For simplicity, inhibiting the APIC access page is sticky.
> */
> if (apic_x2apic_mode(vcpu->arch.apic) &&
> !kvm_x86_ops.has_hardware_x2apic_virtualization)
Hrm, that's not quite right either since it's obviously possible to have an Intel
CPU that supports APICv but not x2APIC virtualization. And in that case KVM
doesn't need to inhibit the memslot, e.g. if not all vCPUs are in x2APIC.
I was hoping to have a name that communicate _why_ the memslot needs to be
inhibited, but it's turning out to be really hard to come up with a name that's
descriptive without being ridiculously verbose. The best I've come up with is:
allow_apicv_in_x2apic_without_x2apic_virtualization
It's heinous, but I'm inclined to go with it unless someone has a better idea.
next prev parent reply other threads:[~2022-12-16 19:40 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-01 0:58 [PATCH v4 00/32] KVM: x86: AVIC and local APIC fixes+cleanups Sean Christopherson
2022-10-01 0:58 ` [PATCH v4 01/32] KVM: x86: Blindly get current x2APIC reg value on "nodecode write" traps Sean Christopherson
2022-12-08 21:47 ` Maxim Levitsky
2022-10-01 0:58 ` [PATCH v4 02/32] KVM: x86: Purge "highest ISR" cache when updating APICv state Sean Christopherson
2022-12-08 21:47 ` Maxim Levitsky
2022-10-01 0:58 ` [PATCH v4 03/32] KVM: SVM: Flush the "current" TLB when activating AVIC Sean Christopherson
[not found] ` <b9f336f17eec6bfbb8429700e0f135d19813c576.camel@redhat.com>
2022-12-08 21:52 ` Maxim Levitsky
2022-12-09 0:40 ` Sean Christopherson
2022-12-08 22:02 ` Maxim Levitsky
2022-10-01 0:58 ` [PATCH v4 04/32] KVM: SVM: Process ICR on AVIC IPI delivery failure due to invalid target Sean Christopherson
2022-10-01 0:58 ` [PATCH v4 05/32] KVM: x86: Don't inhibit APICv/AVIC on xAPIC ID "change" if APIC is disabled Sean Christopherson
2022-12-08 21:53 ` Maxim Levitsky
2022-10-01 0:58 ` [PATCH v4 06/32] KVM: x86: Track xAPIC ID only on userspace SET, _after_ vAPIC is updated Sean Christopherson
2022-12-08 21:53 ` Maxim Levitsky
2022-10-01 0:58 ` [PATCH v4 07/32] KVM: x86: Don't inhibit APICv/AVIC if xAPIC ID mismatch is due to 32-bit ID Sean Christopherson
2022-12-08 21:53 ` Maxim Levitsky
2022-10-01 0:58 ` [PATCH v4 08/32] KVM: SVM: Don't put/load AVIC when setting virtual APIC mode Sean Christopherson
2022-12-08 21:53 ` Maxim Levitsky
2022-10-01 0:58 ` [PATCH v4 09/32] KVM: x86: Handle APICv updates for APIC "mode" changes via request Sean Christopherson
2022-12-08 21:54 ` Maxim Levitsky
2022-10-01 0:58 ` [PATCH v4 10/32] KVM: x86: Move APIC access page helper to common x86 code Sean Christopherson
2022-12-08 21:55 ` Maxim Levitsky
2022-10-01 0:58 ` [PATCH v4 11/32] KVM: x86: Inhibit APIC memslot if x2APIC and AVIC are enabled Sean Christopherson
2022-12-08 21:56 ` Maxim Levitsky
2022-12-16 19:03 ` Sean Christopherson
2022-12-16 19:40 ` Sean Christopherson [this message]
2022-12-27 11:25 ` Paolo Bonzini
2023-01-03 16:30 ` Sean Christopherson
2022-10-01 0:58 ` [PATCH v4 12/32] KVM: SVM: Replace "avic_mode" enum with "x2avic_enabled" boolean Sean Christopherson
2022-10-01 0:58 ` [PATCH v4 13/32] KVM: SVM: Compute dest based on sender's x2APIC status for AVIC kick Sean Christopherson
2022-10-01 0:58 ` [PATCH v4 14/32] KVM: SVM: Fix x2APIC Logical ID calculation for avic_kick_target_vcpus_fast Sean Christopherson
2022-10-01 0:58 ` [PATCH v4 15/32] Revert "KVM: SVM: Use target APIC ID to complete x2AVIC IRQs when possible" Sean Christopherson
2022-12-08 21:56 ` Maxim Levitsky
2022-10-01 0:58 ` [PATCH v4 16/32] KVM: SVM: Document that vCPU ID == APIC ID in AVIC kick fastpatch Sean Christopherson
2022-10-01 0:59 ` [PATCH v4 17/32] KVM: SVM: Add helper to perform final AVIC "kick" of single vCPU Sean Christopherson
2022-10-01 0:59 ` [PATCH v4 18/32] KVM: x86: Explicitly skip optimized logical map setup if vCPU's LDR==0 Sean Christopherson
2022-12-08 21:56 ` Maxim Levitsky
2022-10-01 0:59 ` [PATCH v4 19/32] KVM: x86: Explicitly track all possibilities for APIC map's logical modes Sean Christopherson
2022-12-08 21:57 ` Maxim Levitsky
2022-12-16 18:39 ` Sean Christopherson
2022-12-16 23:34 ` Sean Christopherson
2022-12-27 11:30 ` Paolo Bonzini
2022-10-01 0:59 ` [PATCH v4 20/32] KVM: x86: Skip redundant x2APIC logical mode optimized cluster setup Sean Christopherson
2022-12-08 21:57 ` Maxim Levitsky
2022-10-01 0:59 ` [PATCH v4 21/32] KVM: x86: Disable APIC logical map if logical ID covers multiple MDAs Sean Christopherson
2022-10-01 0:59 ` [PATCH v4 22/32] KVM: x86: Disable APIC logical map if vCPUs are aliased in logical mode Sean Christopherson
2022-10-01 0:59 ` [PATCH v4 23/32] KVM: x86: Honor architectural behavior for aliased 8-bit APIC IDs Sean Christopherson
2022-12-08 21:58 ` Maxim Levitsky
2022-10-01 0:59 ` [PATCH v4 24/32] KVM: x86: Inhibit APICv/AVIC if the optimized physical map is disabled Sean Christopherson
2022-12-08 21:58 ` Maxim Levitsky
2022-12-09 0:56 ` Sean Christopherson
2022-10-01 0:59 ` [PATCH v4 25/32] KVM: SVM: Inhibit AVIC if vCPUs are aliased in logical mode Sean Christopherson
2022-12-08 21:58 ` Maxim Levitsky
2022-10-01 0:59 ` [PATCH v4 26/32] KVM: SVM: Always update local APIC on writes to logical dest register Sean Christopherson
2022-12-08 21:58 ` Maxim Levitsky
2022-10-01 0:59 ` [PATCH v4 27/32] KVM: SVM: Update svm->ldr_reg cache even if LDR is "bad" Sean Christopherson
2022-12-08 21:59 ` Maxim Levitsky
2022-12-09 0:49 ` Sean Christopherson
2022-10-01 0:59 ` [PATCH v4 28/32] KVM: SVM: Require logical ID to be power-of-2 for AVIC entry Sean Christopherson
2022-12-08 22:00 ` Maxim Levitsky
2022-12-29 8:27 ` mlevitsk
2023-01-04 10:08 ` Maxim Levitsky
2023-01-04 18:02 ` Sean Christopherson
2023-01-04 18:34 ` Maxim Levitsky
2022-10-01 0:59 ` [PATCH v4 29/32] KVM: SVM: Handle multiple logical targets in AVIC kick fastpath Sean Christopherson
2022-12-08 22:00 ` Maxim Levitsky
2022-10-01 0:59 ` [PATCH v4 30/32] KVM: SVM: Ignore writes to Remote Read Data on AVIC write traps Sean Christopherson
2022-10-01 0:59 ` [PATCH v4 31/32] Revert "KVM: SVM: Do not throw warning when calling avic_vcpu_load on a running vcpu" Sean Christopherson
2022-12-08 22:01 ` Maxim Levitsky
2022-10-01 0:59 ` [PATCH v4 32/32] KVM: x86: Track required APICv inhibits with variable, not callback Sean Christopherson
2022-12-08 22:03 ` Maxim Levitsky
2022-12-27 11:22 ` [PATCH v4 00/32] KVM: x86: AVIC and local APIC fixes+cleanups Paolo Bonzini
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