ACK: [PATCH Xenial SRU] KVM: PPC: Book3S PR: Fix illegal opcode emulation

[Colin Ian King]

On 09/01/17 20:07, Tim Gardner wrote:
> From: Thomas Huth <thuth at redhat.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1634129
> 
> If kvmppc_handle_exit_pr() calls kvmppc_emulate_instruction() to emulate
> one instruction (in the BOOK3S_INTERRUPT_H_EMUL_ASSIST case), it calls
> kvmppc_core_queue_program() afterwards if kvmppc_emulate_instruction()
> returned EMULATE_FAIL, so the guest gets an program interrupt for the
> illegal opcode.
> However, the kvmppc_emulate_instruction() also tried to inject a
> program exception for this already, so the program interrupt gets
> injected twice and the return address in srr0 gets destroyed.
> All other callers of kvmppc_emulate_instruction() are also injecting
> a program interrupt, and since the callers have the right knowledge
> about the srr1 flags that should be used, it is the function
> kvmppc_emulate_instruction() that should _not_ inject program
> interrupts, so remove the kvmppc_core_queue_program() here.
> 
> This fixes the issue discovered by Laurent Vivier with kvm-unit-tests
> where the logs are filled with these messages when the test tries
> to execute an illegal instruction:
> 
>      Couldn't emulate instruction 0x00000000 (op 0 xop 0)
>      kvmppc_handle_exit_pr: emulation at 700 failed (00000000)
> 
> Signed-off-by: Thomas Huth <thuth at redhat.com>
> Reviewed-by: Alexander Graf <agraf at suse.de>
> Tested-by: Laurent Vivier <lvivier at redhat.com>
> Signed-off-by: Paul Mackerras <paulus at ozlabs.org>
> (cherry picked from commit 708e75a3ee750dce1072134e630d66c4e6eaf63c)
> Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
> ---
>  arch/powerpc/kvm/emulate.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
> index 5cc2e7a..b379146 100644
> --- a/arch/powerpc/kvm/emulate.c
> +++ b/arch/powerpc/kvm/emulate.c
> @@ -302,7 +302,6 @@ int kvmppc_emulate_instruction(struct kvm_run *run, struct kvm_vcpu *vcpu)
>  			advance = 0;
>  			printk(KERN_ERR "Couldn't emulate instruction 0x%08x "
>  			       "(op %d xop %d)\n", inst, get_op(inst), get_xop(inst));
> -			kvmppc_core_queue_program(vcpu, 0);
>  		}
>  	}
>  
> 
Seems to do what it says in the description, so..

Acked-by: Colin Ian King <colin.king at canonical.com>