Re: [patch v6 12/12] btrace, x86: disable on some processors

H.J. Lu
2012-12-17T17:37:16Z

On Mon, Dec 17, 2012 at 8:01 AM, <markus.t.metzger@intel.com> wrote:
> From: Markus Metzger <markus.t.metzger@intel.com>
>
> LBR, BTM, or BTS records may have incorrect branch "from" information afer an
> EIST transition, T-states, C1E, or Adaptive Thermal Throttling (AAJ122).
>
> This results in sporadic test fails. Disable btrace on those processors.
>
> 2012-12-17 Markus Metzger <markus.t.metzger@intel.com>
>
> * common/linux-btrace.c (linux_supports_btrace): Add cpuid check.
>
>
> ---
> gdb/common/linux-btrace.c | 43 +++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 43 insertions(+), 0 deletions(-)
>
> diff --git a/gdb/common/linux-btrace.c b/gdb/common/linux-btrace.c
> index 1231ccc..b5a41a5 100644
> --- a/gdb/common/linux-btrace.c
> +++ b/gdb/common/linux-btrace.c
> @@ -247,7 +247,50 @@ perf_event_read_bts (struct btrace_target_info* tinfo, const uint8_t *begin,
> int
> linux_supports_btrace (void)
> {
> +#if defined(__i386__) || defined(__x86_64__)
> + {
> + unsigned int cpuid, model, family;
> +
> + __asm__ __volatile__ ("movl $1, %%eax;"
> + "cpuid;"
> + : "=a" (cpuid)
> + :: "%ebx", "%ecx", "%edx");
> +
> + family = (cpuid >> 8) & 0xf;
> + model = (cpuid >> 4) & 0xf;
>
> + switch (family)
> + {
> + case 6:
> + model += (cpuid >> 12) & 0xf0;

Do you need to verify that it is an Intel processor before
checking extended family/model?

> + switch (model)
> + {
> + case 26: /* Nehalem */
> + case 30:
> + case 46:

I believe model 31 is also Nehalem. BTW, most Intel documents
use hex number, not decimal for model numbers.

> + case 37: /* Westmere */
> + case 44:
> + case 47:
> + case 42: /* Sandy Bridge */
> + case 45:
> + case 58: /* Ivy Bridge */
> +
> + /* AAJ122: LBR, BTM, or BTS records may have incorrect branch
> + "from" information afer an EIST transition, T-states, C1E, or
> + Adaptive Thermal Throttling. */
> + return 0;
> + }
> + }
> + }
> +
> return 1;
> +
> +#else /* defined(__i386__) || defined(__x86_64__) */
> +
> + return 0;
> +
> +#endif /* defined(__i386__) || defined(__x86_64__) */
> }
>
> /* See linux-btrace.h. */
> --
> 1.7.6.5
>

--
H.J.