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

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Date:	Tue, 22 Mar 2016 11:11:18 +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
Subject: Re: [PATCH] kvm-pr: manage illegal instructions

Hi,

as Paolo has merged the test into kvm-unit-tests, this patch (and
original bug) can be now tested with it.

    git://git.kernel.org/pub/scm/virt/kvm/kvm-unit-tests.git

at least:

    be9b007 powerpc: add test to check invalid instruction trap

Run this with KVM-PR and check your dmesg:

qemu-system-ppc64 -machine pseries,accel=kvm \
                  -bios powerpc/boot_rom.bin \
                  -display none -serial stdio \
                  -kernel powerpc/emulator.elf -smp 1

Laurent

On 15/03/2016 21:18, 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@...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:
>