From: "Jan Beulich" <JBeulich@novell.com>
To: Keir Fraser <keir.xen@gmail.com>
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
"winston.l.wang" <winston.l.wang@intel.com>
Subject: Re: [PATCH] x86: don't write_tsc() non-zero values on CPUs updating only the lower 32 bits
Date: Thu, 14 Apr 2011 08:42:07 +0100 [thread overview]
Message-ID: <4DA6C16F020000780003B899@vpn.id2.novell.com> (raw)
In-Reply-To: <C9CC6014.164FF%keir.xen@gmail.com>
>>> On 14.04.11 at 09:25, Keir Fraser <keir.xen@gmail.com> wrote:
> On 14/04/2011 08:18, "Jan Beulich" <JBeulich@novell.com> wrote:
>
>> This means suppressing the uses in time_calibration_tsc_rendezvous(),
>> cstate_restore_tsc(), and synchronize_tsc_slave(), and fixes a boot
>> hang of Linux Dom0 when loading processor.ko on such systems that
>> have support for C states above C1.
>
> Should your new test be gated on !X86_FEATURE_TSC_RELIABLE? We already
Which test? The write-TSC-probe itself?
> *never* write the TSC when boot_cpu_has(TSC_RELIABLE) -- Dan Magenheimer
> made that change on the assumption that TSCs were globally synced by
> firmware in this case, and us writing one or more TSCs could only ever make
> things worse.
That's not true - we only avoid the writing for TSC sync during boot.
Post-boot bringup of CPUs will write the TSC no matter what, and
cstate_restore_tsc() also has no such gating afaics.
Jan
next prev parent reply other threads:[~2011-04-14 7:42 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-14 7:18 [PATCH] x86: don't write_tsc() non-zero values on CPUs updating only the lower 32 bits Jan Beulich
2011-04-14 7:25 ` Keir Fraser
2011-04-14 7:42 ` Jan Beulich [this message]
2011-04-14 7:50 ` Keir Fraser
2011-04-14 8:06 ` Jan Beulich
2011-04-14 9:18 ` Keir Fraser
2011-04-14 22:41 ` Dan Magenheimer
2011-04-15 6:40 ` Keir Fraser
2011-04-15 14:34 ` Dan Magenheimer
2011-04-15 17:28 ` Keir Fraser
2011-04-14 7:28 ` Jan Beulich
2011-04-14 16:05 ` Keir Fraser
2011-04-14 16:28 ` Jan Beulich
2011-04-14 16:48 ` Keir Fraser
2011-04-14 18:33 ` Wang, Winston L
2011-04-14 21:06 ` Keir Fraser
2011-04-14 21:37 ` Wang, Winston L
2011-04-15 7:06 ` Jan Beulich
2011-04-15 7:08 ` Jan Beulich
2011-04-15 7:37 ` Keir Fraser
2011-04-15 14:49 ` Wang, Winston L
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