Re: [PATCH v2 for-4.8] x86/emul: Move CPUID Faulting fault generation into the emulator

[Wei Liu <wei.liu2@citrix.com>]

On Wed, Oct 26, 2016 at 01:58:02PM +0100, Andrew Cooper wrote:
> In hindsight, this is a better position for it, as it avoids opencoding
> hvmemul_inject_hw_exception() in hvmemul_cpuid(), and reduces the requirements
> on other ops->cpuid() hooks wanting to implement cpuid faulting in the future.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Reviewed-by: Wei Liu <wei.liu2@citrix.com>

Subject to Jan's review / ack:

Release-acked-by: Wei Liu <wei.liu2@citrix.com>

> ---
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> 
> v2:
>  * Expand the cpuid() hook comment in x86_emulate.h
>  * Adjust how the exception is generated
> ---
>  xen/arch/x86/hvm/emulate.c             | 11 -----------
>  xen/arch/x86/x86_emulate/x86_emulate.c |  5 ++++-
>  xen/arch/x86/x86_emulate/x86_emulate.h |  7 ++++++-
>  3 files changed, 10 insertions(+), 13 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
> index 70c8d44..5b408f8 100644
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -1556,18 +1556,7 @@ static int hvmemul_cpuid(
>       */
>      if ( ctxt->opcode == X86EMUL_OPC(0x0f, 0xa2) &&
>           hvm_check_cpuid_faulting(current) )
> -    {
> -        struct hvm_emulate_ctxt *hvmemul_ctxt =
> -            container_of(ctxt, struct hvm_emulate_ctxt, ctxt);
> -
> -        hvmemul_ctxt->exn_pending = 1;
> -        hvmemul_ctxt->trap.vector = TRAP_gp_fault;
> -        hvmemul_ctxt->trap.type = X86_EVENTTYPE_HW_EXCEPTION;
> -        hvmemul_ctxt->trap.error_code = 0;
> -        hvmemul_ctxt->trap.insn_len = 0;
> -
>          return X86EMUL_EXCEPTION;
> -    }
>  
>      hvm_funcs.cpuid_intercept(eax, ebx, ecx, edx);
>      return X86EMUL_OKAY;
> diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
> index a1821d5..2b087e5 100644
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -5011,7 +5011,10 @@ x86_emulate(
>          unsigned int eax = _regs.eax, ebx = _regs.ebx;
>          unsigned int ecx = _regs.ecx, edx = _regs.edx;
>          fail_if(ops->cpuid == NULL);
> -        if ( (rc = ops->cpuid(&eax, &ebx, &ecx, &edx, ctxt)) != 0 )
> +        rc = ops->cpuid(&eax, &ebx, &ecx, &edx, ctxt);
> +        generate_exception_if(rc == X86EMUL_EXCEPTION,
> +                              EXC_GP, 0); /* CPUID Faulting? */
> +        if ( rc != X86EMUL_OKAY )
>              goto done;
>          _regs.eax = eax; _regs.ebx = ebx;
>          _regs.ecx = ecx; _regs.edx = edx;
> diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h b/xen/arch/x86/x86_emulate/x86_emulate.h
> index 641711e..fc8d234 100644
> --- a/xen/arch/x86/x86_emulate/x86_emulate.h
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.h
> @@ -352,7 +352,12 @@ struct x86_emulate_ops
>      int (*wbinvd)(
>          struct x86_emulate_ctxt *ctxt);
>  
> -    /* cpuid: Emulate CPUID via given set of EAX-EDX inputs/outputs. */
> +    /*
> +     * cpuid: Emulate CPUID via given set of EAX-EDX inputs/outputs.
> +     *
> +     * May return X86EMUL_EXCEPTION, which causes the emulator to inject
> +     * #GP[0].  Used to implement CPUID faulting.
> +     */
>      int (*cpuid)(
>          unsigned int *eax,
>          unsigned int *ebx,
> -- 
> 2.1.4
> 

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