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

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

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index b7c4149cb91ca103e0e60438cabc78fcd09ae8d1..aa3720c0b8fee4d9b9e76e64923e7bf08c127ed8 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -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