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

[ Upstream commit e485f6c751e0a969327336c635ca602feea117f0 ]

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: 4423eb5ae32e ("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
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 784ea3289c84018a0e05d8616dbf4d97b9eec9ac..0b656b897f997e8e709ba0997fd22a6f3b11b1a5 100644 (file)
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -592,16 +592,6 @@ 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 */
        }
 

diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index ce25b28cf418ef6154fd46fad165c21c62c90b7b..d76376ce7291eb83d5fbd0c3badd9d8b38c41a00 100644 (file)
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -559,15 +559,43 @@ _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