diff options
| author | Sean Christopherson <seanjc@google.com> | 2025-08-05 12:05:11 -0700 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2025-08-19 11:59:32 -0700 |
| commit | 777414340085711cafd3807a72c531107c0ff7f6 (patch) | |
| tree | ffbfa1a11638237c6611c257dcea50ddd8515c69 /arch/x86/kvm/x86.c | |
| parent | 15daa58e78cef70945324db162d1afbf3f493fb6 (diff) | |
KVM: x86: Only allow "fast" IPIs in fastpath WRMSR(X2APIC_ICR) handler
Explicitly restrict fastpath ICR writes to IPIs that are "fast", i.e. can
be delivered without having to walk all vCPUs, and that target at most 16
vCPUs. Artificially restricting ICR writes to physical mode guarantees
at most one vCPU will receive in IPI (because x2APIC IDs are read-only),
but that delivery might not be "fast". E.g. even if the vCPU exists, KVM
might have to iterate over 4096 vCPUs to find the right one.
Limiting delivery to fast IPIs aligns the WRMSR fastpath with
kvm_arch_set_irq_inatomic() (which also runs with IRQs disabled), and will
allow dropping the semi-arbitrary restrictions on delivery mode and type.
Link: https://lore.kernel.org/r/20250805190526.1453366-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5dc32f2fe391..1b64c71458a2 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2150,7 +2150,7 @@ static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data ((data & APIC_DEST_MASK) == APIC_DEST_PHYSICAL) && ((data & APIC_MODE_MASK) == APIC_DM_FIXED) && ((u32)(data >> 32) != X2APIC_BROADCAST)) - return kvm_x2apic_icr_write(vcpu->arch.apic, data); + return kvm_x2apic_icr_write_fast(vcpu->arch.apic, data); return 1; } |