From 65722736c3baf29e02e964a09e85c9ef71c48e8d Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Sat, 22 Oct 2022 15:22:07 +1000 Subject: [PATCH] powerpc/64s/interrupt: Fix clear of PACA_IRQS_HARD_DIS when returning to soft-masked context Commit a4cb3651a1743 ("powerpc/64s/interrupt: Fix lost interrupts when returning to soft-masked context") fixed the problem of pending irqs being cleared when clearing the HARD_DIS bit, but then it didn't clear the bit at all. This change clears HARD_DIS without affecting other bits in the mask. When an interrupt hits in a soft-masked section that has MSR[EE]=1, it can hard disable and set PACA_IRQS_HARD_DIS, which must be cleared when returning to the EE=1 caller (unless it was set due to a MUST_HARD_MASK interrupt becoming pending). Failure to clear this leaves the returned-to context running with MSR[EE]=1 and PACA_IRQS_HARD_DIS, which confuses irq assertions and could be dangerous for code that might test the flag. This was observed in a hash MMU kernel where a kernel hash fault hits in a local_irqs_disabled region that has EE=1. The hash fault also runs with EE=1, then as it returns, a decrementer hits in the restart section and the irq restart code hard-masks which sets the PACA_IRQ_HARD_DIS flag, which is not clear when the original context is returned to. Reported-by: Sachin Sant Fixes: a4cb3651a1743 ("powerpc/64s/interrupt: Fix lost interrupts when returning to soft-masked context") Signed-off-by: Nicholas Piggin Tested-by: Sachin Sant Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20221022052207.471328-1-npiggin@gmail.com --- arch/powerpc/kernel/interrupt_64.S | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S index 978a173..a019ed6 100644 --- a/arch/powerpc/kernel/interrupt_64.S +++ b/arch/powerpc/kernel/interrupt_64.S @@ -532,15 +532,24 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_kernel) * Returning to soft-disabled context. * Check if a MUST_HARD_MASK interrupt has become pending, in which * case we need to disable MSR[EE] in the return context. + * + * The MSR[EE] check catches among other things the short incoherency + * in hard_irq_disable() between clearing MSR[EE] and setting + * PACA_IRQ_HARD_DIS. */ ld r12,_MSR(r1) andi. r10,r12,MSR_EE beq .Lfast_kernel_interrupt_return_\srr\() // EE already disabled lbz r11,PACAIRQHAPPENED(r13) andi. r10,r11,PACA_IRQ_MUST_HARD_MASK - beq .Lfast_kernel_interrupt_return_\srr\() // No HARD_MASK pending + bne 1f // HARD_MASK is pending + // No HARD_MASK pending, clear possible HARD_DIS set by interrupt + andi. r11,r11,(~PACA_IRQ_HARD_DIS)@l + stb r11,PACAIRQHAPPENED(r13) + b .Lfast_kernel_interrupt_return_\srr\() + - /* Must clear MSR_EE from _MSR */ +1: /* Must clear MSR_EE from _MSR */ #ifdef CONFIG_PPC_BOOK3S li r10,0 /* Clear valid before changing _MSR */ -- 2.7.4