linux-kernel - [PATCH 3/8] KVM: VMX: Ensure vIRR isn't reloaded at odd times when sync'ing PIR

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250315030630.2371712-4-seanjc@google.com>
Date: Fri, 14 Mar 2025 20:06:24 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	Jacob Pan <jacob.jun.pan@...ux.intel.com>, Jim Mattson <jmattson@...gle.com>
Subject: [PATCH 3/8] KVM: VMX: Ensure vIRR isn't reloaded at odd times when
 sync'ing PIR

Read each vIRR exactly once when shuffling IRQs from the PIR to the vAPIC
to ensure getting the highest priority IRQ from the chunk doesn't reload
from the vIRR.  In practice, a reload is functionally benign as vcpu->mutex
is held and so IRQs can be consumed, i.e. new IRQs can appear, but existing
IRQs can't disappear.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/lapic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 9dbc0f5d9865..cb4aeab914eb 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -667,7 +667,7 @@ bool __kvm_apic_update_irr(u32 *pir, void *regs, int *max_irr)
 	for (i = vec = 0; i <= 7; i++, vec += 32) {
 		u32 *p_irr = (u32 *)(regs + APIC_IRR + i * 0x10);
 
-		irr_val = *p_irr;
+		irr_val = READ_ONCE(*p_irr);
 		pir_val = READ_ONCE(pir[i]);
 
 		if (pir_val) {
-- 
2.49.0.rc1.451.g8f38331e32-goog