Re: [Xen-devel] [PATCH v2 2/2] x86/Intel: virtualize support for cpuid faulting

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 14/10/16 20:28, Kyle Huey wrote:
>> :) I am now curious as to which bit I missed.
> I made these changes.
>
> - Kyle
>
> ---
>  tests/cpuid-faulting/main.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/tests/cpuid-faulting/main.c b/tests/cpuid-faulting/main.c
> index 3e782a2..221567d 100644
> --- a/tests/cpuid-faulting/main.c
> +++ b/tests/cpuid-faulting/main.c
> @@ -37,36 +37,39 @@ bool ex_record_fault_ebx(struct cpu_regs *regs,
>  }
>  
>  unsigned int stub_rdmsr(uint32_t idx, uint64_t *val)
>  {
>      unsigned int fault = 0;
>      uint32_t lo, hi;
>  
>      *val = 0;
> -    asm volatile("1: rdmsr; 2:"
> +    asm volatile("1: rdmsr;"
> +                 "xor %%ebx, %%ebx; 2:"
>                   _ASM_EXTABLE_HANDLER(1b, 2b, ex_record_fault_ebx)
>                   : "=a" (lo), "=d" (hi), "=&b" (fault)

Ah - this should be +b rather than =&b, which avoids modifying the assembly.

>                   : "c" (idx));
>  
>      if ( !fault )
>          *val = (((uint64_t)hi) << 32) | lo;
>  
>      return fault;
>  }
>  
>  unsigned int stub_wrmsr(uint32_t idx, uint64_t val)
>  {
>      unsigned int fault = 0;
>  
> -    asm volatile("1: rdmsr; 2:"
> +    asm volatile("1: wrmsr;"

Oops.

~Andrew

> "xor %%ebx, %%ebx; 2:"
>                   _ASM_EXTABLE_HANDLER(1b, 2b, ex_record_fault_ebx)
>                   : "=&b" (fault)
>                   : "c" (idx), "a" ((uint32_t)val),
> -                   "d" ((uint32_t)(val >> 32)));
> +                   "d" ((uint32_t)(val >> 32))
> +                 : "memory");
>  
>      return fault;
>  }
>  
>  unsigned long stub_cpuid(void)
>  {
>      unsigned int fault = 0;
>  
>
> base-commit: 0342fd279b05d0c2e31c8418fcffcdc9e48eb42f


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