Re: [Xen-devel] EFI GetNextVariableName crashes when running under Xen, but not under Linux. efi-rs=0 works. No memmap issues

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.01.15 at 18:20, <konrad.wilk@xxxxxxxxxx> wrote:
> On Wed, Jan 28, 2015 at 04:56:02PM +0000, Jan Beulich wrote:
>> >>> On 28.01.15 at 17:17, <daniel.kiper@xxxxxxxxxx> wrote:
>> > On Wed, Jan 28, 2015 at 11:03:19AM -0500, Konrad Rzeszutek Wilk wrote:
>> >> I am not really sure of what the work-around should be in Xen except
>> >> making SetVirtualAddressMap work..
>> > 
>> > Hmmm... Crazy idea. IIRC, we use RS in 1:1 mapping. If we need to call
>> > SetVirtualAddressMap() then force it to create 1:1 mapping. Is it
>> > possible? Could you try it? I think you should play with code just
>> > before SetVirtualAddressMap().
>> 
>> Of course this is possible. The reason we don't call the function is
>> kexec: How would the secondary kernel be able to make runtime
>> calls if we already established some mapping? Remember that
>> SetVirtualAddressMap() may not be called more than once...
> 
> Linux does seem to have the code to deal with this, via bootparams.
> See git  1fec0533693cd74f2d1a46edd29449cfee429df0
> Author: Dave Young <dyoung@xxxxxxxxxx>
> Date:   Fri Dec 20 18:02:19 2013 +0800
> 
>     x86/efi: Pass necessary EFI data for kexec via setup_data
> 
> 456a29ddada79198c5965300e04103c40c481f62
> Author: Dave Young <dyoung@xxxxxxxxxx>
> Date:   Fri Dec 20 18:02:20 2013 +0800
> 
>     x86: Add xloadflags bit for EFI runtime support on kexec

Compare the dates of these with that of the Xen commit(s) enabling
EFI support. Plus - this protocol is absolutely Linux-centric afaict,
whereas Xen's kexec interface/support should be as generic as
possible.

> ..that could be employed. The problem I had was that I tried to employ
> SetVirtualAddressMap in the Xen code - but it did not work at all.
> 
> Jan, do you want me to send you an serial log with a Xen code with
> SetVirtualAddressMap executed  -on a non-Lenovo machine to eliminate
> the firmware issues?

Not sure what that would be good for: The commented out code is
there just for documentation purposes. It was never expected that
you could simply enable it and expect it to work (albeit I _very_
vaguely recall it having worked very early on during development of
the EFI support code).

Considering how broken the EFI appears to be on that laptop, why
don't you simply turn it off (just like is required on many other
systems with too early versions of it - reportedly in some cases
turning it on renders systems un-bootable, with it being very difficult
to turn it back off; I'm supposedly even in possession of such a
system, but guess what - I don't want to try it out).

Jan


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