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powerpc/64s/exception: machine check pseries should skip the late handler for kernel MCEs

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The powernv machine check handler copes with taking a MCE from one of
three contexts, guest, kernel, and user. In each case the early
handler runs first on a special stack, then:

- The guest case branches to the KVM interrupt handler (via standard
  interrupt macros).
- The user case will run the "late" handler which is like a normal
  interrupt that runs in virtual mode and uses the regular kernel
  stack.
- The kernel case queues the event and schedules it for processing
  with irq work.

The last case is important, it must not enable virtual memory because
the MMU state may not be set up to deal with that (e.g., SLB might be
clear), it must not use the regular kernel stack for similar reasons
(e.g., might be in OPAL with OPAL stack in r1), and the kernel does
not expect anything to touch its stack if interrupts are disabled.

The pseries handler does not do this queueing, but instead it always
runs the late handler for host MCEs, which has some of the same
problems.

Now that pseries is using machine_check_events, change it to do the
same as powernv and queue events for kernel MCEs.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190802105709.27696-11-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2019-08-02 20:56:35 +10:00 committed by Michael Ellerman
parent 9ca766f989
commit 272f636445
1 changed files with 2 additions and 20 deletions
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22
arch/powerpc/kernel/exceptions-64s.S
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@ -1163,7 +1163,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)
cmpdi r3,0 /* see if we handled MCE successfully */
beq 1b /* if !handled then panic */
BEGIN_FTR_SECTION
/*
* Return from MC interrupt.
* Queue up the MCE event so that we can log it later, while
@ -1172,18 +1172,7 @@ BEGIN_FTR_SECTION
bl machine_check_queue_event
MACHINE_CHECK_HANDLER_WINDUP
RFI_TO_KERNEL
FTR_SECTION_ELSE
/*
* pSeries: Return from MC interrupt. Before that stay on emergency
* stack and call machine_check_exception to log the MCE event.
*/
LOAD_HANDLER(r10,mce_return)
mtspr SPRN_SRR0,r10
ld r10,PACAKMSR(r13)
mtspr SPRN_SRR1,r10
RFI_TO_KERNEL
b .
ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE)
9:
/* Deliver the machine check to host kernel in V mode. */
BEGIN_FTR_SECTION
@ -1212,13 +1201,6 @@ EXC_COMMON_BEGIN(unrecover_mce)
bl unrecoverable_exception
b 1b
EXC_COMMON_BEGIN(mce_return)
/* Invoke machine_check_exception to print MCE event and return. */
addi r3,r1,STACK_FRAME_OVERHEAD
bl machine_check_exception
MACHINE_CHECK_HANDLER_WINDUP
RFI_TO_KERNEL
b .
EXC_REAL_BEGIN(data_access, 0x300, 0x80)
EXCEPTION_PROLOG_0 PACA_EXGEN