Re: [PATCH] misc/xenmicrocode: Upload /lib/firmware/<some blob> to the hypervisor

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Thu, Jan 29, 2015 at 06:34:23PM +0000, Andrew Cooper wrote:
> <snip>
> Getting this conversation back on topic.
> 
> The current state of play in Xen is this:
> 
> * Boot time microcode loading exists (by scanning uncompressed cpio
> multiboot modules) and should be safe to use.

Please note that it does require passing in 'ucode=scan' on the Xen
command line and does not do it automatically. It would be nice
if that was automatic..
> 
> * The facility for runtime microcode loading exists (via privileged
> hypercall), but is unsafe to use at present, especially if virtual
> machines are running.  There are several steps which can be taken to
> make it safer to use.
> 
> 
> There is a plausible usecase for runtime microcode loading for people
> who wish to take that risk, and as such, xenmicrocode is useful utility
> to have, but it should probably not be available by default until we
> believe the hypervisor side of the interface avoids the known potholes.

Aren't these issues the same if we had an runtime microcode
implementation (I am referring to the xen-microcode driver that
Jeremy wrote once and some distros have in their kernel). The loading
of microcode is done the same was as baremetal via 'rescan' interface.
> 
> ~Andrew
> 
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