6.15-stable review patch. If anyone has any objections, please let me know.
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From: Sean Christopherson seanjc@google.com
[ Upstream commit 600e9606046ac3b9b7a3f0500d08a179df84c45e ]
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 Link: https://lore.kernel.org/r/20250401163447.846608-2-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/irq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index 81f9b78e0f7ba..6cd5d2d6c58af 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])