Re: [Xen-devel] [PATCH OSSTEST] Arrange to upgrade microcode on x86 test hosts.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.06.15 at 12:52, <ian.campbell@xxxxxxxxxx> wrote:
> Both Xen and Linux support extracting a microcode update from an
> initramfs early during boot. This requires prepending a suitable
> uncompressed cpio archive containing the necessary files to the
> initrd.
> 
> Xen also supports loading the microcode cpio from any multiboot
> module, but for in order to allow the possibility of loading on native
> boots (e.g. for build jobs) we prefer the prepend method.
> 
> This patch provides mg-cpu-microcode-update which creates a suitable
> microcode cpio in the images directory and arranges for it to be added
> to the host during installation (so it is done before the kernel is
> installed and initramfs generated etc, saving faff). It also adds
> "ucode=scan" to the Xen command line when necessary.
> 
> The version of initramfs-tools in Wheezy does not yet support
> prepending things to the initrm, so we use a custom compression
> command which sneakily does it for us. This could be done better from
> Jessie onwards.
> 
> Note that Linux only supports this from v3.8 onwards, so this doesn't
> work for Wheezy (which uses v3.2). From Jessie onwards we should
> benefit from microcode updates even for native (build) jobs.
> 
> Tested on both Intel and AMD where it appeared to have the desired
> effect under Xen. Under native I only tried Wheezy which doesn't
> support early microcode.
> 
> Note that I've not bothered to implement late microcode updates, which
> would work on v3.2 too, since that would need a different set of files
> etc and it doesn't seem especially pressing.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Cc: Jan Beulich <JBeulich@xxxxxxxx>

Thanks for doing this so quickly, Ian!

Jan


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