On Wed, Oct 12, 2016 at 12:13:08PM +0200, Grzegorz Andrejczuk wrote:
> If processor is Intel Xeon Phi we enable user-level mwait feature.
> Enabling this feature suppreses invalid-opcode error, when MONITOR/MWAIT
> is called from ring 3.
>
> Change-Id: I1c7defb99296b022790a068a6c725b3e860cd68c
> Signed-off-by: Grzegorz Andrejczuk <grzegorz.andrejc...@intel.com>
> ---
> arch/x86/kernel/cpu/intel.c | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> index fcd484d..7f0f01a 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -61,6 +61,14 @@ void check_mpx_erratum(struct cpuinfo_x86 *c)
> }
> }
>
> +static int phir3mwait = 1;
> +static int __init phir3mwait_disable(char *value)
> +{
> + phir3mwait = 0;
> + return 1;
> +}
> +__setup("intel-phir3mwait=disable", phir3mwait_disable);
That's a lot of typing on the cmdline. "r3mwait=disable" looks just as
fine to me, for example.
> static void early_init_intel(struct cpuinfo_x86 *c)
> {
> u64 misc_enable;
> @@ -211,6 +219,24 @@ static void early_init_intel(struct cpuinfo_x86 *c)
> }
>
> check_mpx_erratum(c);
> +
> + /*
> + * Setting ring 3 MONITOR/MWAIT for all threads
> + * when CPU is Xeon Phi Family x200
> + * This can be disabled with phir3mwait=disable cmdline switch.
> + * We preserve the reserved values and set only 2nd bit.
> + * Ref:
> + *
> https://software.intel.com/en-us/blogs/2016/10/06/intel-xeon-phi-product-family-x200-knl-user-mode-ring-3-monitor-and-mwait
> + */
> + if (c->x86 == 6 &&
> + c->x86_model == INTEL_FAM6_XEON_PHI_KNL &&
> + phir3mwait) {
> + u64 prev;
> +
> + rdmsrl(MSR_PHI_MISC_THD_FEATURE_ENABLE, prev);
> + wrmsrl(MSR_PHI_MISC_THD_FEATURE_ENABLE,
> + prev | MSR_PHI_MISC_THD_FEATURE_ENABLE_R3MWAIT);
Wanna test the MSR_PHI_MISC_THD_FEATURE_ENABLE_R3MWAIT bit before doing
the MSR write?
Btw, you might want to shorten those define names - they're huuge.
--
Regards/Gruss,
Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284
(AG Nürnberg)
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