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KVM: PPC: e500mc: add load inst fixup

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There's always a chance we're unable to read a guest instruction. The guest
could have its TLB mapped execute-, but not readable, something odd happens
and our TLB gets flushed. So it's a good idea to be prepared for that case
and have a fallback that allows us to fix things up in that case.

Add fixup code that keeps guest code from potentially crashing our host kernel.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Alexander Graf 2012-02-15 23:24:28 +00:00 • committed by Avi Kivity
commit 1d628af78a
1 changed files with 29 additions and 1 deletions
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30
arch/powerpc/kvm/bookehv_interrupts.S
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@ -28,6 +28,7 @@
#include <asm/asm-compat.h>
#include <asm/asm-offsets.h>
#include <asm/bitsperlong.h>
#include <asm/thread_info.h>
#include "../kernel/head_booke.h" /* for THREAD_NORMSAVE() */
@ -171,9 +172,36 @@
PPC_STL r30, VCPU_GPR(r30)(r4)
PPC_STL r31, VCPU_GPR(r31)(r4)
mtspr SPRN_EPLC, r8
/* disable preemption, so we are sure we hit the fixup handler */
#ifdef CONFIG_PPC64
clrrdi r8,r1,THREAD_SHIFT
#else
rlwinm r8,r1,0,0,31-THREAD_SHIFT /* current thread_info */
#endif
li r7, 1
stw r7, TI_PREEMPT(r8)
isync
lwepx r9, 0, r5
/*
* In case the read goes wrong, we catch it and write an invalid value
* in LAST_INST instead.
*/
1: lwepx r9, 0, r5
2:
.section .fixup, "ax"
3: li r9, KVM_INST_FETCH_FAILED
b 2b
.previous
.section __ex_table,"a"
PPC_LONG_ALIGN
PPC_LONG 1b,3b
.previous
mtspr SPRN_EPLC, r3
li r7, 0
stw r7, TI_PREEMPT(r8)
stw r9, VCPU_LAST_INST(r4)
.endif