Re: [PATCH] kvm-pr: manage illegal instructions

From: Alexander Graf
Date: Wed May 11 2016 - 06:35:52 EST


On 03/15/2016 09:18 PM, Laurent Vivier wrote:
While writing some instruction tests for kvm-unit-tests for powerpc,
I've found that illegal instructions are not managed correctly with kvm-pr,
while it is fine with kvm-hv.

When an illegal instruction (like ".long 0") is processed by kvm-pr,
the kernel logs are filled with:

Couldn't emulate instruction 0x00000000 (op 0 xop 0)
kvmppc_handle_exit_pr: emulation at 700 failed (00000000)

While the exception handler receives an interrupt for each instruction
executed after the illegal instruction.

Signed-off-by: Laurent Vivier <lvivier@xxxxxxxxxx>
---
arch/powerpc/kvm/book3s_emulate.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
index 2afdb9c..4ee969d 100644
--- a/arch/powerpc/kvm/book3s_emulate.c
+++ b/arch/powerpc/kvm/book3s_emulate.c
@@ -99,7 +99,6 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
switch (get_op(inst)) {
case 0:
- emulated = EMULATE_FAIL;
if ((kvmppc_get_msr(vcpu) & MSR_LE) &&
(inst == swab32(inst_sc))) {
/*
@@ -112,6 +111,9 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
kvmppc_set_gpr(vcpu, 3, EV_UNIMPLEMENTED);
kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
emulated = EMULATE_DONE;
+ } else {
+ kvmppc_core_queue_program(vcpu, SRR1_PROGILL);

But isn't that exactly what the semantic of EMULATE_FAIL is? Fixing it up in book3s_emulate.c is definitely the wrong spot.

So what is the problem you're trying to solve? Is the SRR0 at the wrong spot or are the log messages the problem?


Alex