From: Segher Boessenkool <segher@kernel.crashing.org>
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>,
Timur Tabi <timur@freescale.com>
Subject: Re: [PATCH] powerpc/85xx: disable timebase synchronization under the hypervisor
Date: Fri, 24 Jun 2011 04:36:00 +0200 [thread overview]
Message-ID: <59f786bfaced051a14e2bb75d3d1ce77@kernel.crashing.org> (raw)
In-Reply-To: <20110623124802.7aeb6b66@schlenkerla.am.freescale.net>
>> But does that mean that a guest should never be allowed to modify a
>> virtualized
>> timebase register, even if the hypervisor can support it?
>
> The book3e mtspr writeup doesn't appear to specify the behavior when
> writing to a read-only SPR, so perhaps you could argue that something
> other
> than a no-op is implementation-specific behavior.
v2.06 III-E 9.2.1:
"Writing the Time Base is hypervisor privileged."
v2.06 III-E 2.1:
"If a hypervisor-privileged register is accessed in the guest supervisor
state (MSR[GS PR] = 0b10), an Embedded Hypervisor Privilege exception
occurs."
(v2.06 III-E 5.4.1, the big SPR table, also shows the TB regs (for
writing,
i.e. 284 and 285) to be hypervisor privileged. Consistency, hurray :-)
)
Segher
next prev parent reply other threads:[~2011-06-24 2:34 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
2011-06-23 17:48 ` Scott Wood
2011-06-24 2:36 ` Segher Boessenkool [this message]
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
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