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KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context() 

Commit 863771a28e ("powerpc/32s: Convert switch_mmu_context() to C")
moved the switch_mmu_context() to C. While in principle a good idea, it
meant that the function now uses the stack. The stack is not accessible
from real mode though.

So to keep calling the function, let's turn on MSR_DR while we call it.
That way, all pointer references to the stack are handled virtually.

In addition, make sure to save/restore r12 on the stack, as it may get
clobbered by the C function.

Fixes: 863771a28e ("powerpc/32s: Convert switch_mmu_context() to C")
Cc: stable@vger.kernel.org # v5.14+
Reported-by: Matt Evans <matt@ozlabs.org>
Signed-off-by: Alexander Graf <graf@amazon.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220510123717.24508-1-graf@amazon.com
This commit is contained in:
Alexander Graf 2022-05-10 14:37:17 +02:00 committed by Michael Ellerman
parent 348c713441
commit ee8348496c
1 changed files with 21 additions and 5 deletions
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26
arch/powerpc/kvm/book3s_32_sr.S
View File

@ -122,11 +122,27 @@
/* 0x0 - 0xb */
/* 'current->mm' needs to be in r4 */
tophys(r4, r2)
lwz r4, MM(r4)
tophys(r4, r4)
/* This only clobbers r0, r3, r4 and r5 */
/* switch_mmu_context() needs paging, let's enable it */
mfmsr r9
ori r11, r9, MSR_DR
mtmsr r11
sync
/* switch_mmu_context() clobbers r12, rescue it */
SAVE_GPR(12, r1)
/* Calling switch_mmu_context(<inv>, current->mm, <inv>); */
lwz r4, MM(r2)
bl switch_mmu_context
/* restore r12 */
REST_GPR(12, r1)
/* Disable paging again */
mfmsr r9
li r6, MSR_DR
andc r9, r9, r6
mtmsr r9
sync
.endm