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| author | Maxim Levitsky <mlevitsk@redhat.com> | 2023-07-26 16:59:43 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2023-07-29 11:05:24 -0400 |
| commit | 514946d1436341bae57f647ee633cef5edb19ee2 (patch) | |
| tree | d7e96c23f99d909a44427c9600dfa0e267b02027 /arch | |
| parent | 6eaae198076080886b9e7d57f4ae06fa782f90ef (diff) | |
| download | lwn-514946d1436341bae57f647ee633cef5edb19ee2.tar.gz lwn-514946d1436341bae57f647ee633cef5edb19ee2.zip | |
KVM: x86: VMX: __kvm_apic_update_irr must update the IRR atomically
If APICv is inhibited, then IPIs from peer vCPUs are done by
atomically setting bits in IRR.
This means, that when __kvm_apic_update_irr copies PIR to IRR,
it has to modify IRR atomically as well.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20230726135945.260841-2-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/lapic.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 113ca9661ab2..b17b37e4d4fc 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -637,16 +637,22 @@ bool __kvm_apic_update_irr(u32 *pir, void *regs, int *max_irr) *max_irr = -1; for (i = vec = 0; i <= 7; i++, vec += 32) { + u32 *p_irr = (u32 *)(regs + APIC_IRR + i * 0x10); + + irr_val = *p_irr; pir_val = READ_ONCE(pir[i]); - irr_val = *((u32 *)(regs + APIC_IRR + i * 0x10)); + if (pir_val) { + pir_val = xchg(&pir[i], 0); + prev_irr_val = irr_val; - irr_val |= xchg(&pir[i], 0); - *((u32 *)(regs + APIC_IRR + i * 0x10)) = irr_val; - if (prev_irr_val != irr_val) { - max_updated_irr = - __fls(irr_val ^ prev_irr_val) + vec; - } + do { + irr_val = prev_irr_val | pir_val; + } while (prev_irr_val != irr_val && + !try_cmpxchg(p_irr, &prev_irr_val, irr_val)); + + if (prev_irr_val != irr_val) + max_updated_irr = __fls(irr_val ^ prev_irr_val) + vec; } if (irr_val) *max_irr = __fls(irr_val) + vec; |