From: Blue Swirl <blauwirbel@gmail.com>
To: Alexander Graf <agraf@suse.de>
Cc: QEMU Developers <qemu-devel@nongnu.org>,
Aurelien Jarno <aurelien@aurel32.net>
Subject: [Qemu-devel] Re: [PATCH] PPC: tell the guest about the time base frequency
Date: Fri, 8 Jan 2010 18:04:02 +0000 [thread overview]
Message-ID: <f43fc5581001081004s2f4ebf06vd09284e9a0559471@mail.gmail.com> (raw)
In-Reply-To: <1262972592-7317-1-git-send-email-agraf@suse.de>
On Fri, Jan 8, 2010 at 5:43 PM, Alexander Graf <agraf@suse.de> wrote:
> Our guest systems need to know by how much the timebase increases every second,
> so there usually is a "timebase-frequency" property in the cpu leaf of the
> device tree.
>
> This property is missing in OpenBIOS, as is the "clock-frequency" property that
> tells the guest how fast the CPU is. FWIW that one is only used for
> /proc/cpuinfo though.
>
> With qemu, Linux's fallback timebase speed and qemu's internal timebase speed
> match up. With KVM, that is no longer true. The guest is running at the same
> timebase speed as the host.
>
> This leads to massive timing problems. On my test machine, a "sleep 2" takes
> about 14 seconds with KVM enabled.
>
> This patch exports the timebase and clock frequencies to OpenBIOS, so it can
> then put them into the device tree. I'll push the OpenBIOS change with the
> NewWorld patch set, once that's either been reviewed or applied.
IIRC copying the host CPU frequency to guest was rejected earlier for x86.
next prev parent reply other threads:[~2010-01-08 18:04 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-08 17:43 [Qemu-devel] [PATCH] PPC: tell the guest about the time base frequency Alexander Graf
2010-01-08 18:04 ` Blue Swirl [this message]
2010-01-08 18:07 ` [Qemu-devel] " Alexander Graf
2010-01-08 18:22 ` Blue Swirl
2010-01-08 18:27 ` Alexander Graf
2010-01-08 18:29 ` Blue Swirl
2010-01-08 18:37 ` Alexander Graf
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