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powerpc/64/interrupt: Fix return to masked context after hard-mask irq becomes pending

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If a synchronous interrupt (e.g., hash fault) is taken inside an
irqs-disabled region which has MSR[EE]=1, then an asynchronous interrupt
that is PACA_IRQ_MUST_HARD_MASK (e.g., PMI) is taken inside the
synchronous interrupt handler, then the synchronous interrupt will
return with MSR[EE]=1 and the asynchronous interrupt fires again.

If the asynchronous interrupt is a PMI and the original context does not
have PMIs disabled (only Linux IRQs), the asynchronous interrupt will
fire despite having the PMI marked soft pending. This can confuse the
perf code and cause warnings.

This patch changes the interrupt return so that irqs-disabled MSR[EE]=1
contexts will be returned to with MSR[EE]=0 if a PACA_IRQ_MUST_HARD_MASK
interrupt has become pending in the meantime.

The longer explanation for what happens:
1. local_irq_disable()
2. Hash fault interrupt fires, do_hash_fault handler runs
3. interrupt_enter_prepare() sets IRQS_ALL_DISABLED
4. interrupt_enter_prepare() sets MSR[EE]=1
5. PMU interrupt fires, masked handler runs
6. Masked handler marks PMI pending
7. Masked handler returns with PACA_IRQ_HARD_DIS set, MSR[EE]=0
8. do_hash_fault interrupt return handler runs
9. interrupt_exit_kernel_prepare() clears PACA_IRQ_HARD_DIS
10. interrupt returns with MSR[EE]=1
11. PMU interrupt fires, perf handler runs

Fixes: 4423eb5ae3 ("powerpc/64/interrupt: make normal synchronous interrupts enable MSR[EE] if possible")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220926054305.2671436-4-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2022-09-26 15:43:01 +10:00 committed by Michael Ellerman
parent 799f7063c7
commit e485f6c751
2 changed files with 31 additions and 13 deletions
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10
arch/powerpc/kernel/interrupt.c
View File

@ -431,16 +431,6 @@ again:
if (unlikely(stack_store))
__hard_EE_RI_disable();
/*
* Returning to a kernel context with local irqs disabled.
* Here, if EE was enabled in the interrupted context, enable
* it on return as well. A problem exists here where a soft
* masked interrupt may have cleared MSR[EE] and set HARD_DIS
* here, and it will still exist on return to the caller. This
* will be resolved by the masked interrupt firing again.
*/
if (regs->msr & MSR_EE)
local_paca->irq_happened &= ~PACA_IRQ_HARD_DIS;
#endif /* CONFIG_PPC64 */
}

34
arch/powerpc/kernel/interrupt_64.S
View File

@ -526,15 +526,43 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_kernel)
ld r11,SOFTE(r1)
cmpwi r11,IRQS_ENABLED
stb r11,PACAIRQSOFTMASK(r13)
bne 1f
beq .Linterrupt_return_\srr\()_soft_enabled
/*
* 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.
*/
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 1f // No HARD_MASK pending
/* Must clear MSR_EE from _MSR */
#ifdef CONFIG_PPC_BOOK3S
li r10,0
/* Clear valid before changing _MSR */
.ifc \srr,srr
stb r10,PACASRR_VALID(r13)
.else
stb r10,PACAHSRR_VALID(r13)
.endif
#endif
xori r12,r12,MSR_EE
std r12,_MSR(r1)
b .Lfast_kernel_interrupt_return_\srr\()
.Linterrupt_return_\srr\()_soft_enabled:
#ifdef CONFIG_PPC_BOOK3S
lbz r11,PACAIRQHAPPENED(r13)
andi. r11,r11,(~PACA_IRQ_HARD_DIS)@l
bne- interrupt_return_\srr\()_kernel_restart
#endif
li r11,0
stb r11,PACAIRQHAPPENED(r13) # clear out possible HARD_DIS
1:
li r11,0
stb r11,PACAIRQHAPPENED(r13) // clear the possible HARD_DIS
.Lfast_kernel_interrupt_return_\srr\():
cmpdi cr1,r3,0