KVM: SVM: Limit AVIC physical max index based on configured max_vcpu_ids

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[ Upstream commit 574ef752d4 ]

KVM allows VMMs to specify the maximum possible APIC ID for a virtual
machine through KVM_CAP_MAX_VCPU_ID capability so as to limit data
structures related to APIC/x2APIC. Utilize the same to set the AVIC
physical max index in the VMCB, similar to VMX. This helps hardware
limit the number of entries to be scanned in the physical APIC ID table
speeding up IPI broadcasts for virtual machines with smaller number of
vCPUs.

Unlike VMX, SVM AVIC requires a single page to be allocated for the
Physical APIC ID table and the Logical APIC ID table, so retain the
existing approach of allocating those during VM init.

Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
Link: https://lore.kernel.org/r/adb07ccdb3394cd79cb372ba6bcc69a4e4d4ef54.1757009416.git.naveen@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Stable-dep-of: 87d0f901a9 ("KVM: SVM: Set/clear CR8 write interception when AVIC is (de)activated")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Naveen N Rao 2026-03-16 15:11:51 -04:00 • committed by Greg Kroah-Hartman

parent b7493f48c3

commit ba28a0dcc4

1 changed files with 5 additions and 2 deletions

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arch/x86/kvm/svm/avic.c

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