linux-kernel - [PATCH] kvm-pr: manage illegal instructions

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Date:	Tue, 15 Mar 2016 21:18:37 +0100
From:	Laurent Vivier <lvivier@...hat.com>
To:	kvm-ppc@...r.kernel.org, kvm@...r.kernel.org
Cc:	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Alexander Graf <agraf@...e.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	Laurent Vivier <lvivier@...hat.com>
Subject: [PATCH] kvm-pr: manage illegal instructions

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@...hat.com>
---
 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);
+			emulated = EMULATE_AGAIN;
 		}
 		break;
 	case 19:
-- 
2.5.0