Re: [PATCH 5/7 v3] KVM: PPC: exit to user space on "ehpriv" instruction

["tiejun.chen" <tiejun.chen@windriver.com>]

On 04/08/2013 06:32 PM, Bharat Bhushan wrote:
> From: Bharat Bhushan <bharat.bhushan@freescale.com>
>
> "ehpriv" instruction is used for setting software breakpoints
> by user space. This patch adds support to exit to user space
> with "run->debug" have relevant information.
>
> Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
> ---
>   arch/powerpc/kvm/e500_emulate.c |   10 ++++++++++
>   1 files changed, 10 insertions(+), 0 deletions(-)
>
> diff --git a/arch/powerpc/kvm/e500_emulate.c b/arch/powerpc/kvm/e500_emulate.c
> index e78f353..cefdd38 100644
> --- a/arch/powerpc/kvm/e500_emulate.c
> +++ b/arch/powerpc/kvm/e500_emulate.c
> @@ -26,6 +26,7 @@
>   #define XOP_TLBRE   946
>   #define XOP_TLBWE   978
>   #define XOP_TLBILX  18
> +#define XOP_EHPRIV  270
>
>   #ifdef CONFIG_KVM_E500MC
>   static int dbell2prio(ulong param)
> @@ -130,6 +131,15 @@ int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
>   			emulated = kvmppc_e500_emul_tlbivax(vcpu, ea);
>   			break;
>
> +		case XOP_EHPRIV:
> +			run->exit_reason = KVM_EXIT_DEBUG;

IIRC, the ehpriv instruction should generate a Hypervisor Privilege Exception to 
trap into the Hypervisor proactive. And we can use this ability to design 
something conveniently. And so, that is not only for the debug mechanism like 
you did.

So here if 'run->exit_reason' is fixed to KVM_EXIT_DEBUG, how to distinguish 
other scenarios? So as I understand, we should use 'ehpriv oc' exactly then 
resolve 'oc' further to go different cases, right?

Tiejun

> +			run->debug.arch.address = vcpu->arch.pc;
> +			run->debug.arch.status = 0;
> +			kvmppc_account_exit(vcpu, DEBUG_EXITS);
> +			emulated = EMULATE_EXIT_USER;
> +			*advance = 0;
> +			break;
> +
>   		default:
>   			emulated = EMULATE_FAIL;
>   		}
>