linux-kernel - Re: [PATCH] x86/tsc: Use rdtsc_ordered() when RDTSCP or LFENCE

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Message-ID: <979c3fc3-33d3-49fa-af80-52ec09325a08@kernel.org>
Date: Sun, 25 Aug 2024 07:37:45 -0500
From: Mario Limonciello <superm1@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>, Bjorn Helgaas
 <bhelgaas@...gle.com>, Mathias Nyman <mathias.nyman@...el.com>,
 Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc: "open list : PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>,
 "open list : USB XHCI DRIVER" <linux-usb@...r.kernel.org>,
 Daniel Drake <drake@...lessos.org>, Gary Li <Gary.Li@....com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH] x86/tsc: Use rdtsc_ordered() when RDTSCP or LFENCE_RDTSC
 are supported



On 8/25/24 07:22, Thomas Gleixner wrote:
> On Thu, Aug 22 2024 at 23:25, Mario Limonciello wrote:
> 
> Why is this hidden in a reply to the middle of a PCI patch series?
> 
> Sigh.

As I mentioned in my reply I didn't mean for this to go out at this 
time.  Sorry for the noise!

It's still under testing that it REALLY helps things.
It was in my working directory and I totally missed it when I sent this 
PCI series.

> 
>> From: Mario Limonciello <mario.limonciello@....com>
>>
>> On AMD processors the TSC has been reported drifting on and off for
>> various platforms.  This has been root caused to becaused by out of order
>> TSC and HPET counter values.  When the SoC supports RDTSCP or LFENCE_RDTSC
>> use ordered tsc reads instead.
> 
> This really wants a fixes tag.

Yes; assuming it really helps I will send it properly with tags and to 
the right lists.