[POWERPC] Fix PMU + soft interrupt disable bug (44387e9f) · Commits · 戴 / test

Since the PMU is an NMI now, it can come at any time we are only soft disabled. We must hard disable around the two places we allow the kernel stack SLB and r1 to go out of sync. Otherwise the PMU exception can force a kernel stack SLB into another slot, which can lead to it getting evicted, which can lead to a nasty unrecoverable SLB miss in the exception entry code. Signed-off-by:

Anton Blanchard <anton@samba.org> Acked-by:

Benjamin Herrenschmidt <benh@kernel.crashing.org> Acked-by:

Olof Johansson <olof@lixom.net> Signed-off-by:

Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/process.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -353,6 +353,12 @@ struct task_struct __switch_to(struct task_struct prev,
		account_process_vtime(current);
		calculate_steal_time();

		/*
		* We can't take a PMU exception inside _switch() since there is a
		* window where the kernel stack SLB and the kernel stack are out
		* of sync. Hard disable here.
		*/
		hard_irq_disable();
		last = _switch(old_thread, new_thread);

		local_irq_restore(flags);

arch/powerpc/mm/slb.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -124,6 +124,12 @@ void slb_flush_and_rebolt(void)
		ksp_vsid_data = get_slb_shadow()->save_area[2].vsid;
		}

		/*
		* We can't take a PMU exception in the following code, so hard
		* disable interrupts.
		*/
		hard_irq_disable();

		/* We need to do this all in asm, so we're sure we don't touch
		* the stack between the slbia and rebolting it. */
		asm volatile("isync\n"

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