Re: [Xen-devel] Current state of Xen microcode (Was: Re: uploading 3.16~rc5-1~exp1)

[Ben Hutchings <ben@xxxxxxxxxxxxxxx>]

On Tue, 2014-07-15 at 11:35 -0400, Konrad Rzeszutek Wilk wrote:
> On Tue, Jul 15, 2014 at 04:06:00PM +0100, Ian Campbell wrote:
> > On Tue, 2014-07-15 at 10:59 -0400, Konrad Rzeszutek Wilk wrote:
> > > On Tue, Jul 15, 2014 at 09:53:32AM +0100, Ian Campbell wrote:
> > > > Adding xen-devel and some of the Linux maints,
> > > > 
> > > > On Mon, 2014-07-14 at 23:22 +0200, maximilian attems wrote:
> > > > > I will upload tomorrow Tuesday around 22h00 UT to experimental.
> > > > > 
> > > > > There are two TODOS concerning the not yet forwarded Debian patches:
> > > > > - cgroups
> > > > > - xen microcode
> > > > > 
> > > > > 
> > > > > I consider both not a blocker, but would be happy if Xen guys could
> > > > > have a look for what is needed.
> > > > 
> > > > The xen microcode patches which maks is referring to are these:
> > > > http://anonscm.debian.org/viewvc/kernel/dists/trunk/linux/debian/patches/features/all/xen/
> > > > which are a forward port of Jeremy's old microcode_xen.ko driver.
> > > 
> > > They are also at my branch
> > > http://git.kernel.org/cgit/linux/kernel/git/konrad/xen.git/log/?h=stable/misc
> > > 
> > > Hm, I should rebase them at some point.
> > > > 
> > > > I've not been keeping up on Xen x86 microcode stuff these days but I
> > > > think we don't need this any more with modern Xen since we can parse the
> > > > microcode blob off the front of the initrd, is that right?
> > > 
> > > Right. And best of it, the support for that is in dracut so
> > > it automatically can happen (thought you still need to add
> > > 'ucode=scan' in the /etc/default/grub.cfg in the GRUB_CMDLINE_XEN
> > > parameter) and also in /etc/dracut.conf add 'early_microcode=yes'.
> > 
> > Hrm, I thought it was transparent. Debian doesn't use dracut, it uses
> > initramfs-tools. So perhaps there is some work to be done here.
> > 
> > I understand ucode=scan, but what does the dracut option do?
> 
> Packages the blobs and sticks them to the initramfs.
> 
> I think 'initframfs-tools' will need some code there.
[...]

initramfs-tools can already prepend microcode in the way Linux expects.
I assume Xen supports the same format (it's a little weird for it to be
parsing the dom0 initrd, but OK...).  But we're presumably missing the
GRUB integration to get 'ucode=scan' added automatically.

Ben.

-- 
Ben Hutchings
Hoare's Law of Large Problems:
        Inside every large problem is a small problem struggling to get out.

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