From: Keir Fraser <keir.xen@gmail.com>
To: Jan Beulich <JBeulich@novell.com>
Cc: "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: Fri, 15 Apr 2011 08:37:23 +0100 [thread overview]
Message-ID: <C9CDB443.1661B%keir.xen@gmail.com> (raw)
In-Reply-To: <4DA80B1A020000780003C875@vpn.id2.novell.com>
On 15/04/2011 08:08, "Jan Beulich" <JBeulich@novell.com> wrote:
>> But the write is actually tsc + 4*(s32)(tmp-tsc), and tmp has 1U<<32 ORed
>> into it (because it was read after your second write to the TSC. Perhaps we
>> should just write back the full original tsc and call that good enough?
>
> Again, note the (s32) cast.
Oh yes. Still the 4x is weird, and on this path (!TSC_RELIABLE, TSC is fully
writable) we will sync all AP TSCs as they come up anyway. So writing back
the original TSC value is good enough, as far as this matters at all (which
it probably doesn't).
-- Keir
next prev parent reply other threads:[~2011-04-15 7:37 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
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 [this message]
2011-04-15 14:49 ` Wang, Winston L
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