[MODERATED] Re: [PATCH 3/9] TAA 3

[Pawan Gupta <pawan.kumar.gupta@linux.intel.com>]

On Thu, Oct 24, 2019 at 06:39:35PM +0100, speck for Andrew Cooper wrote:
> On 23/10/2019 10:01, speck for Pawan Gupta wrote:
> > +	if (tsx_ctrl_state == TSX_CTRL_DISABLE) {
> > +		tsx_disable();
> > +
> > +		/*
> > +		 * tsx_disable() will change the state of the
> > +		 * RTM CPUID bit.  Clear it here since it is now
> > +		 * expected to be not set.
> > +		 */
> > +		setup_clear_cpu_cap(X86_FEATURE_RTM);
> 
> This same argument applies to HLE, and it would be weird for
> pre-TSX_CTRL CPUs with tsx=off to report HLE but not RTM in /proc/cpuid

I guess you mean post-TSX_CTRL CPUs. I think this was done intentionally
to reduce an extra cloud pool scenario. I will confirm if this is the
case.

> Furthermore, while grepping through the tree, I found
> 
> events/intel/lbr.c-267-static inline bool
> lbr_from_signext_quirk_needed(void)
> events/intel/lbr.c-268-{
> events/intel/lbr.c-269- int lbr_format = x86_pmu.intel_cap.lbr_format;
> events/intel/lbr.c:270: bool tsx_support = boot_cpu_has(X86_FEATURE_HLE) ||
> events/intel/lbr.c-271-                    boot_cpu_has(X86_FEATURE_RTM);
> events/intel/lbr.c-272-
> events/intel/lbr.c-273- return !tsx_support && (lbr_desc[lbr_format] &
> LBR_TSX);
> 
> which is going to need an adjustment to avoid applying the quirks on
> non-broken hardware.

This may need an adjustment. I will get back on this one too.

Thanks,
Pawan