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@xxxxxxx> --- v1 -> v2: - fix whitespace - use explicit preempt counts --- arch/powerpc/kvm/bookehv_interrupts.S | 30 +++++++++++++++++++++++++++++- 1 files changed, 29 insertions(+), 1 deletions(-) diff --git a/arch/powerpc/kvm/bookehv_interrupts.S b/arch/powerpc/kvm/bookehv_interrupts.S index 63023ae..f7dc3f6 100644 --- a/arch/powerpc/kvm/bookehv_interrupts.S +++ b/arch/powerpc/kvm/bookehv_interrupts.S @@ -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 -- 1.6.0.2 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
