Re: 2.6.25-rc1 xen pvops regression

Jeremy Fitzhardinge
2008-02-20T22:00:47Z

Ian Campbell wrote:
> On Tue, 2008-02-19 at 23:43 -0800, H. Peter Anvin wrote:
>
>> Ian Campbell wrote:
>>
>>> On Mon, 2008-02-18 at 02:40 -0800, Joel Becker wrote:
>>>
>>>> On Sun, Feb 17, 2008 at 06:49:21PM +0000, Ian Campbell wrote:
>>>>
>>>>> x86/xen: Do not scan for DMI unless the DMI region is reserved by e820.
>>>>>
>>>> This fixed it. I'm now booting successfully. Thank you!
>>>>
>>> Excellent. Jeremy, are you happy for this to go in?
>>>

I had no problem with it, but Peter's objection seems substantial enough.

> As far as the actual change goes I was assuming that any machine that
> has DMI/SMBIOS would easily be new enough to have an E820 which could be
> expected to reserve this region. Looks like I was mistaken about how
> long E820 had been around and/or how reliably it is used to reserve the
> tables.
>
> Anyway, will have to think of another solution.
>

Well, the way we've handled this kind of thing elsewhere is to just
reserve that pseudophys address space in earlish Xen init code and fill
it with not-DMI things (zero, I guess). It's a bit of a waste of
memory, but maybe we can recover it once DMI has given up and gone
away. This also makes it easy to insert faked-up DMI info if that turns
out to be useful.

J