From: Timur Tabi <timur@freescale•com>
To: Scott Wood <scottwood@freescale•com>
Cc: Wood Scott-B07421 <B07421@freescale•com>,
"linuxppc-dev@ozlabs•org" <linuxppc-dev@ozlabs•org>,
"paulus@samba•org" <paulus@samba•org>,
McClintock Matthew-B29882 <B29882@freescale•com>,
Gala Kumar-B11780 <B11780@freescale•com>
Subject: Re: [PATCH] powerpc/85xx: disable timebase synchronization under the hypervisor
Date: Thu, 23 Jun 2011 12:33:40 -0500 [thread overview]
Message-ID: <4E0378F4.5010501@freescale.com> (raw)
In-Reply-To: <20110623122210.06ee9f55@schlenkerla.am.freescale.net>
Scott Wood wrote:
> From Power ISA 2.06B, book III-E, section 9.2.1:
>
> Virtualized Implementation Note:
>
> In virtualized implementations, TBU and TBL are
> read-only.
But does that mean that a guest should never be allowed to modify a virtualized
timebase register, even if the hypervisor can support it?
>> > So a generic HV mode bit is not going to help me, unless there's also a bit
>> > that's specific to our hypervisor. And even then, we would need some way to
>> > differentiate among different versions of our hypervisor, in case some future
>> > version adds timebase support.
> That's very unlikely to happen.
I know. I was just being architecturally pedantic.
> Ideally we would avoid doing this sync even when not running under a
> hypervisor, as long as firmware has done the sync, and kexec hasn't messed
> it up. Besides being a waste of boot time, the firmware's sync is
> probably tighter since it can use a platform-specific mechanism to start all
> the timebases at once.
I agree with that, but for now, I need to work around that kexec "limitation".
--
Timur Tabi
Linux kernel developer at Freescale
next prev parent reply other threads:[~2011-06-23 17:33 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-14 23:04 [PATCH] powerpc/85xx: disable timebase synchronization under the hypervisor Timur Tabi
2011-06-14 23:14 ` Scott Wood
2011-06-14 23:15 ` Timur Tabi
2011-06-14 23:25 ` Scott Wood
2011-06-15 1:58 ` Benjamin Herrenschmidt
2011-06-15 2:10 ` Tabi Timur-B04825
2011-06-15 2:33 ` Benjamin Herrenschmidt
2011-06-22 11:44 ` Kumar Gala
2011-06-22 14:55 ` Timur Tabi
2011-06-23 17:22 ` Scott Wood
2011-06-23 17:33 ` Timur Tabi [this message]
2011-06-23 17:48 ` Scott Wood
2011-06-24 2:36 ` Segher Boessenkool
2011-06-24 2:38 ` Tabi Timur-B04825
2011-06-24 3:50 ` Segher Boessenkool
2011-06-24 15:16 ` Scott Wood
2011-06-24 23:36 ` Benjamin Herrenschmidt
2011-06-27 13:35 ` Kumar Gala
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4E0378F4.5010501@freescale.com \
--to=timur@freescale$(echo .)com \
--cc=B07421@freescale$(echo .)com \
--cc=B11780@freescale$(echo .)com \
--cc=B29882@freescale$(echo .)com \
--cc=linuxppc-dev@ozlabs$(echo .)org \
--cc=paulus@samba$(echo .)org \
--cc=scottwood@freescale$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox