From: Nicholas Piggin npiggin@gmail.com
commit a4cb3651a174366cc85a677da9e3681fbe97fdae upstream.
It's possible for an interrupt returning to an irqs-disabled context to lose a pending soft-masked irq because it branches to part of the exit code for irqs-enabled contexts, which is meant to clear only the PACA_IRQS_HARD_DIS flag from PACAIRQHAPPENED by zeroing the byte. This just looks like a simple thinko from a recent commit (if there was no hard mask pending, there would be no reason to clear it anyway).
This also adds comment to the code that actually does need to clear the flag.
Fixes: e485f6c751e0a ("powerpc/64/interrupt: Fix return to masked context after hard-mask irq becomes pending") Reported-by: Sachin Sant sachinp@linux.ibm.com Reported-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Nicholas Piggin npiggin@gmail.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20221013064418.1311104-1-npiggin@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/kernel/interrupt_64.S | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-)
--- a/arch/powerpc/kernel/interrupt_64.S +++ b/arch/powerpc/kernel/interrupt_64.S @@ -571,7 +571,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\s beq .Lfast_kernel_interrupt_return_\srr() // EE already disabled lbz r11,PACAIRQHAPPENED(r13) andi. r10,r11,PACA_IRQ_MUST_HARD_MASK - beq 1f // No HARD_MASK pending + beq .Lfast_kernel_interrupt_return_\srr() // No HARD_MASK pending
/* Must clear MSR_EE from _MSR */ #ifdef CONFIG_PPC_BOOK3S @@ -588,12 +588,23 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\s b .Lfast_kernel_interrupt_return_\srr()
.Linterrupt_return_\srr()_soft_enabled: + /* + * In the soft-enabled case, need to double-check that we have no + * pending interrupts that might have come in before we reached the + * restart section of code, and restart the exit so those can be + * handled. + * + * If there are none, it is be possible that the interrupt still + * has PACA_IRQ_HARD_DIS set, which needs to be cleared for the + * interrupted context. This clear will not clobber a new pending + * interrupt coming in, because we're in the restart section, so + * such would return to the restart location. + */ #ifdef CONFIG_PPC_BOOK3S lbz r11,PACAIRQHAPPENED(r13) andi. r11,r11,(~PACA_IRQ_HARD_DIS)@l bne- interrupt_return_\srr()_kernel_restart #endif -1: li r11,0 stb r11,PACAIRQHAPPENED(r13) // clear the possible HARD_DIS