From: Tabi Timur-B04825 <B04825@freescale.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: McClintock Matthew-B29882 <B29882@freescale.com>,
Wood Scott-B07421 <B07421@freescale.com>,
Gala Kumar-B11780 <B11780@freescale.com>,
"paulus@samba.org" <paulus@samba.org>,
"linuxppc-dev@ozlabs.org" <linuxppc-dev@ozlabs.org>
Subject: Re: [PATCH] powerpc/85xx: disable timebase synchronization under the hypervisor
Date: Fri, 24 Jun 2011 02:38:58 +0000 [thread overview]
Message-ID: <4E03F8C1.60706@freescale.com> (raw)
In-Reply-To: <59f786bfaced051a14e2bb75d3d1ce77@kernel.crashing.org>
Segher Boessenkool wrote:
>
> 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] =3D 0b10), an Embedded Hypervisor Privilege exception
> occurs."
>
> (v2.06 III-E 5.4.1, the big SPR table, also shows the TB regs (for writin=
g,
> i.e. 284 and 285) to be hypervisor privileged. Consistency, hurray :-) )
To me, all this means that a guest cannot write to the actual timebase=20
register. I'm not interpreting this to mean that a hypervisor can't=20
virtualize the timebase and allow a guest to read/write a virtual timebase=
=20
register, so that it thinks it's writing to the real hardware timebase regi=
ster.
--=20
Timur Tabi
Linux kernel developer at Freescale=
next prev parent reply other threads:[~2011-06-24 2:39 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
2011-06-24 2:38 ` Tabi Timur-B04825 [this message]
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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