From: Sean Christopherson Date: Tue, 1 Apr 2025 16:34:40 +0000 (-0700) Subject: x86/irq: Ensure initial PIR loads are performed exactly once X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=600e9606046ac3b9b7a3f0500d08a179df84c45e;p=users%2Fjedix%2Flinux-maple.git x86/irq: Ensure initial PIR loads are performed exactly once 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 Link: https://lore.kernel.org/r/20250401163447.846608-2-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index 81f9b78e0f7b..6cd5d2d6c58a 100644 --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -419,7 +419,7 @@ 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])