Actually perhaps it
is easy to fix. The copying of chunks out of the larger microcode buffer seems
to just be a convenience. Perhaps just returning offset pointers into the original
buffer from the get_next_ucode_from_buffer() function would get rid of the
vmalloc() call. Just a thought as I looked at it further.
Thanks
Ross
From:
xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Ross
Philipson
Sent: Monday, September 15, 2008 5:35 PM
To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] Crash in update microcode changes - change set
18475
The changes for CPU
microcode loading that were done recently (change set 18475 in unstable
staging) seem to be causing a crash. I am using an Intel system and I get an
assertion in Xen during the DOM0 boot. This is what I believe is going on.
In
xen/arch/x86/microcode.c the routine do_microcode_update() is dispatching the
update work to each CPU with on_each_cpu() which in turn uses an IPI to
dispatch the callback vector on each CPU. The microcode update routine passed
in is called in the IPI context on the target CPU (including irq_enter() before
calling the ucode function). Within the ucode function the calls eventually get
down to the Intel specific calls in microcode_intel.c. Specifically:
do_microcode_update_one()
microcode_update_cpu()
cpu_request_microcode()
get_next_ucode_from_buffer()
Within the last
call, vmalloc() is called and eventually _xmalloc() asserts on
ASSERT(!in_irq()). I checked and the earlier code, though it dispatched work to
different CPUs with IPIs, did not try to dynamically allocate memory. I am not
sure how to fix this easily without redoing how the whole new microcode
framework works. Also I didn’t look closely at AMD but it may have the same
issue. I can take a crack at fixing it but maybe someone will see a simple
solution.
Thanks
Ross
Ross Philipson
Senior Software Engineer
Citrix Systems, Inc
14 Crosby Drive
Bedford, MA 01730
781-301-7949
ross.philipson@xxxxxxxxxx
