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From: "Suthikulpanit, Suravee" <suravee.suthikulpanit@amd.com>
To: Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Maxim Levitsky <mlevitsk@redhat.com>,
	Li RongQing <lirongqing@baidu.com>
Subject: Re: [PATCH v2 13/23] KVM: x86: Disable APIC logical map if vCPUs are aliased in logical mode
Date: Tue, 13 Sep 2022 18:32:04 -0500	[thread overview]
Message-ID: <aedb7677-528a-75b7-6517-ab1865515ad4@amd.com> (raw)
In-Reply-To: <20220903002254.2411750-14-seanjc@google.com>

Hi Sean

On 9/2/2022 7:22 PM, Sean Christopherson wrote:
> Disable the optimized APIC logical map if multiple vCPUs are aliased to
> the same logical ID.  Architecturally, all CPUs whose logical ID matches
> the MDA are supposed to receive the interrupt; overwriting existing map
> entries can result in missed IPIs.
> 
> Fixes: 1e08ec4a130e ("KVM: optimize apic interrupt delivery")
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>   arch/x86/kvm/lapic.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 6b2f538b8fd0..75748c380ceb 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -303,12 +303,13 @@ void kvm_recalculate_apic_map(struct kvm *kvm)
>   		if (!mask)
>   			continue;
>   
> -		if (!is_power_of_2(mask)) {
> +		ldr = ffs(mask) - 1;
> +		if (!is_power_of_2(mask) || cluster[ldr]) {

Should this be checking if the cluster[ldr] is pointing to the same 
struct apic instead? For example:

		if (!is_power_of_2(mask) || cluster[ldr] != apic)

 From my observation, the kvm_recalculate_apic_map() can be called many 
times, and the cluster[ldr] could have already been assigned from the 
previous invocation. So, as long as it is the same, it should be okay.

Best Regards,
Suravee

>   			new->mode = KVM_APIC_MODE_XAPIC_FLAT |
>   				    KVM_APIC_MODE_XAPIC_CLUSTER;
>   			continue;
>   		}
> -		cluster[ffs(mask) - 1] = apic;
> +		cluster[ldr] = apic;
>   	}
>   out:
>   	old = rcu_dereference_protected(kvm->arch.apic_map,

  reply	other threads:[~2022-09-13 23:32 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-03  0:22 [PATCH v2 00/23] KVM: x86: AVIC and local APIC fixes+cleanups Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 01/23] KVM: x86: Purge "highest ISR" cache when updating APICv state Sean Christopherson
2022-09-05 21:58   ` Paolo Bonzini
2022-09-03  0:22 ` [PATCH v2 02/23] KVM: SVM: Flush the "current" TLB when activating AVIC Sean Christopherson
2022-09-05 21:58   ` Paolo Bonzini
2022-09-03  0:22 ` [PATCH v2 03/23] KVM: SVM: Process ICR on AVIC IPI delivery failure due to invalid target Sean Christopherson
2022-09-05 21:59   ` Paolo Bonzini
2022-09-03  0:22 ` [PATCH v2 04/23] KVM: x86: Inhibit AVIC SPTEs if any vCPU enables x2APIC Sean Christopherson
2022-09-05 22:02   ` Paolo Bonzini
2022-09-13 19:52   ` Suthikulpanit, Suravee
2022-09-14  7:39     ` Sean Christopherson
2022-09-14 17:41       ` Suthikulpanit, Suravee
2022-09-16 17:47         ` Sean Christopherson
2022-09-16 19:10     ` Sean Christopherson
2022-09-20 13:07   ` Maxim Levitsky
2022-09-20 15:46     ` Sean Christopherson
2022-09-20 16:50       ` Sean Christopherson
2022-09-23 10:18         ` Maxim Levitsky
2022-09-23 10:19       ` Maxim Levitsky
2022-09-03  0:22 ` [PATCH v2 05/23] KVM: SVM: Don't put/load AVIC when setting virtual APIC mode Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 06/23] KVM: SVM: Replace "avic_mode" enum with "x2avic_enabled" boolean Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 07/23] KVM: SVM: Compute dest based on sender's x2APIC status for AVIC kick Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 08/23] KVM: SVM: Fix x2APIC Logical ID calculation for avic_kick_target_vcpus_fast Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 09/23] Revert "KVM: SVM: Use target APIC ID to complete x2AVIC IRQs when possible" Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 10/23] KVM: SVM: Document that vCPU ID == APIC ID in AVIC kick fastpatch Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 11/23] KVM: SVM: Add helper to perform final AVIC "kick" of single vCPU Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 12/23] KVM: x86: Disable APIC logical map if logical ID covers multiple MDAs Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 13/23] KVM: x86: Disable APIC logical map if vCPUs are aliased in logical mode Sean Christopherson
2022-09-13 23:32   ` Suthikulpanit, Suravee [this message]
2022-09-14  7:42     ` Sean Christopherson
2022-09-15  2:11       ` Suthikulpanit, Suravee
2022-09-16 18:52         ` Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 14/23] KVM: x86: Honor architectural behavior for aliased 8-bit APIC IDs Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 15/23] KVM: x86: Explicitly skip adding vCPU to optimized logical map if LDR==0 Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 16/23] KVM: x86: Explicitly track all possibilities for APIC map's logical modes Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 17/23] KVM: SVM: Inhibit AVIC if vCPUs are aliased in logical mode Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 18/23] KVM: SVM: Always update local APIC on writes to logical dest register Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 19/23] KVM: SVM: Update svm->ldr_reg cache even if LDR is "bad" Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 20/23] KVM: SVM: Require logical ID to be power-of-2 for AVIC entry Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 21/23] KVM: SVM: Handle multiple logical targets in AVIC kick fastpath Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 22/23] KVM: SVM: Ignore writes to Remote Read Data on AVIC write traps Sean Christopherson
2022-09-03  0:22 ` [PATCH v2 23/23] Revert "KVM: SVM: Do not throw warning when calling avic_vcpu_load on a running vcpu" Sean Christopherson

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