lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Sat, 18 Feb 2017 10:02:07 +0100
From:   Pavel Machek <>
To:     Chen Yu <>
        Len Brown <>,
        "Rafael J. Wysocki" <>,
        Zhang Rui <>,
        Ingo Molnar <>,
Subject: Re: [PATCH][RFC v4] ACPI throttling: Disable the MSR T-state if
 enabled after resumed

On Fri 2017-02-17 16:27:30, Chen Yu wrote:
> Previously a bug was reported that on certain Broadwell
> platform, after resumed from S3, the CPU is running at
> an anomalously low speed, due to the BIOS has enabled the
> MSR throttling across S3. The solution to this was to introduce
> a quirk framework to save/restore tstate MSR register around
> suspend/resume, in Commit 7a9c2dd08ead ("x86/pm:
> Introduce quirk framework to save/restore extra MSR
> registers around suspend/resume").
> However there are still three problems left:
> 1. More and more reports show that other platforms also
>    encountered the same issue, so the quirk list might
>    be endless.
> 2. Each CPUs should take the save/restore operation into
>    consideration, rather than the boot CPU alone.
> 3. Normally ACPI T-state re-evaluation is done on resume,
>    however there is no _TSS on the bogus platform, thus
>    above re-evaluation code does not run on that machine.
> Solution:
> This patch is based on the fact that, we generally should not
> expect the system to come back from resume with throttling
> enabled, but leverage the OS components to deal with it,
> such as thermal event. So we simply clear the MSR T-state
> and print the warning if it is found to be enabled after
> resumed back. Besides, we can remove the quirk in previous patch
> later.

What if the machine _is_ hot? 

> +static int acpi_throttling_init_ops(void)
> +{
> +	/*
> +	 * Reevaluate on boot CPU. Since it is not always CPU0,
> +	 * we can not invoke throttling_msr_reevaluate(0) directly.
> +	 */

Boot cpu is not cpu#0? How can that be?

Should we introduce generic framework to "fix" all the cpus? Actually,
should this be done right on cpu hotplug?

(cesky, pictures)

Download attachment "signature.asc" of type "application/pgp-signature" (182 bytes)

Powered by blists - more mailing lists