From: Anthony Liguori <aliguori@us.ibm.com>
To: Hollis Blanchard <hollisb@us.ibm.com>
Cc: kvm-ppc-devel@lists.sourceforge.net,
Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>,
Rusty Russell <rusty@ozlabs.au.ibm.com>,
kvm-devel <kvm-devel@lists.sourceforge.net>
Subject: Re: [kvm-ppc-devel] booting from virtio-blk
Date: Tue, 01 Apr 2008 17:09:33 +0000 [thread overview]
Message-ID: <47F26C4D.1090406@us.ibm.com> (raw)
In-Reply-To: <1207066432.6214.29.camel@basalt>
Hollis Blanchard wrote:
>
> Thanks Anthony, you've saved me a lot of debug time! Rusty, doing 64-bit
> PCI config space accesses with ioread8() definitely violates the
> principle of least surprises, and would have taken me a long time to
> track down. :(
>
It's the unfortunate side-effect of using PCI config space without
passing it's semantics through to the virtio devices. Right now, you do
a config_get which is basically a memcpy. If we didn't do accesses with
ioread8(), you could potentially have a caller than did a config_get()
of size 4 that didn't intend on having endian conversion applied.
The other option would have been to provide config_get() and
config_get8/16/32/64() the later performing endian conversion.
Regards,
Anthony Liguori
> Attached is a boot log of a PowerPC guest booting from virtio-blk root.
>
> "ramdisk_image" is the standard ~4MB image provided with DENX Embedded
> Linux Development Kit. Booting is also *way* faster than NFS root (a few
> seconds to get to a shell :) .
>
>
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next prev parent reply other threads:[~2008-04-01 17:09 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-01 12:01 [kvm-ppc-devel] [PATCH] kvm(ppc)-userspace: initialize virtio-block ehrhardt
2008-04-01 12:08 ` [kvm-ppc-devel] [PATCH] kvm(ppc)-userspace: initialize Christian Ehrhardt
2008-04-01 14:33 ` [kvm-ppc-devel] [PATCH] kvm(ppc)-userspace: Hollis Blanchard
2008-04-01 14:46 ` [kvm-ppc-devel] [PATCH] kvm(ppc)-userspace: initialize Anthony Liguori
2008-04-01 16:13 ` [kvm-ppc-devel] booting from virtio-blk Hollis Blanchard
2008-04-01 17:05 ` Anthony Liguori
2008-04-01 17:09 ` Anthony Liguori [this message]
2008-04-01 20:36 ` Benjamin Herrenschmidt
2008-04-01 21:03 ` Anthony Liguori
2008-04-01 21:14 ` Benjamin Herrenschmidt
2008-04-01 21:18 ` Hollis Blanchard
2008-04-01 21:24 ` Benjamin Herrenschmidt
2008-04-02 14:52 ` [kvm-ppc-devel] [PATCH] kvm(ppc)-userspace: initialize Anthony Liguori
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