[MODERATED] Re: [PATCH v7 00/10] TAAv7 0

On Mon, Oct 21, 2019 at 02:32:31PM -0700, speck for Andy Lutomirski wrote:
> On 10/21/19 1:22 PM, speck for Pawan Gupta wrote:
> > From: Pawan Gupta <[email protected]>
> > Subject: [PATCH v7 00/10] TAAv7
> > 
> > Changes since v6:
> > - Add Michal's patch to allow tsx=on|off|auto via CONFIG
> > - Rebase to v5.4-rc4
> > - Changelog, comments and documentation update.
> > 
> > Changes since v5:
> > - Remove unsafe X86_FEATURE_RTM toggles.
> 
> I'm wondering if maybe these patches shouldn't touch the cpu
> capabilities at all.  After all, even with TSX toggled off, TSX is still
> present -- XBEGIN doesn't give #UD. By making this change, we avoid
> needing to even consider what happens when a cpu capability bit changes
> after boot.

This would affect some of the PMU related boot_cpu_has() checks.
https://elixir.bootlin.com/linux/latest/source/arch/x86/events/intel/core.c#L3415

> 
> I think it would be nice to expose whether TSX is enabled somewhere in
> sysfs, but I'm not convinced that "features" is the place for it.

Part 10/10 in this series adds support to expose whether TSX is enabled
(only present when TSX_CTRL MSR is supported):

	$ cat /sys/devices/system/cpu/hw_tx_mem

Thanks,
Pawan