Commit a4cb3651a1743 ("powerpc/64s/interrupt: Fix lost interrupts when
returning to soft-masked context") fixed the problem of pending irqs
pending 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 <sach...@linux.ibm.com>
Fixes: a4cb3651a1743 ("powerpc/64s/interrupt: Fix lost interrupts when
returning to soft-masked context")
Signed-off-by: Nicholas Piggin <npig...@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 978a173eb339..a019ed6fc839 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 */
--
2.37.2
