diff mbox series

[v2,1/8] x86/irq: Ensure initial PIR loads are performed exactly once

Message ID 20250401163447.846608-2-seanjc@google.com (mailing list archive)
State New
Headers show
Series x86/irq: KVM: Optimize KVM's PIR harvesting | expand

Commit Message

Sean Christopherson April 1, 2025, 4:34 p.m. UTC 
Ensure the PIR is read exactly once at the start of handle_pending_pir(),
to guarantee that checking for an outstanding posted interrupt in a given
chuck doesn't reload the chunk from the "real" PIR.  Functionally, a reload
is benign, but it would defeat the purpose of pre-loading into a copy.

Fixes: 1b03d82ba15e ("x86/irq: Install posted MSI notification handler")
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kernel/irq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index feca4f20b06a..85fa2db38dc4 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -414,7 +414,7 @@  static __always_inline bool handle_pending_pir(u64 *pir, struct pt_regs *regs)
 	bool handled = false;
 
 	for (i = 0; i < 4; i++)
-		pir_copy[i] = pir[i];
+		pir_copy[i] = READ_ONCE(pir[i]);
 
 	for (i = 0; i < 4; i++) {
 		if (!pir_copy[i])