Re: [Xen-devel] crash in efi_runtime_call

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Apr 17, 2015 at 01:54:28PM +0100, Andrew Cooper wrote:
> On 17/04/15 13:39, Jan Beulich wrote:
> >>>> On 17.04.15 at 13:59, <andrew.cooper3@xxxxxxxxxx> wrote:
> >> On 17/04/15 12:17, Olaf Hering wrote:
> >>> Since booting xen fails on my ProBook unless I specify "maxcpus=1" I
> >>> tried the EFI firmware today. To my surprise it boots and finds all
> >>> cpus. But once some efi driver in dom0 is loaded xen crashes. The same
> >>> happens with xen-4.4 as included in SLE12.
> >>>
> >>> ...
> >>> (XEN) Xen call trace:
> >>> (XEN)    [<00000000aec1e8e1>] 00000000aec1e8e1
> >>> (XEN)    [<ffff82d080222600>] efi_runtime_call+0x7f0/0x890
> >>> (XEN)    [<ffff82d0801641a9>] do_platform_op+0x679/0x1670
> >>> (XEN)    [<ffff82d08021dfb9>] syscall_enter+0xa9/0xae
> >>> ....
> >>>
> >>> Can I do anything about it, or is this a firmware bug? I will move the
> >>> offending efi driver away and try again.
> >>>
> >>> Olaf
> >> This is a firmware bug.
> > +1 (and I'm surprised how common this is)
> 
> The bug is present in the reference implementation code, which means it
> is present in a lot of real firmware.  We have kit from 3 different
> vendors which are affected, including latest available firmware.
> 
> >
> >>> (XEN)  0000100000000-000023fffffff type=7 attr=000000000000000
> >>> (XEN)  00000fec10000-00000fec10fff type=11 attr=8000000000000001
> >>> (XEN)  00000fff40000-00000fff46fff type=11 attr=8000000000000000
> >>> (XEN) Unknown cachability for MFNs 0xfff40-0xfff46
> >> This unknown cacheability causes Xen not to make pagetables for the region.
> >>
> >> There is a patch or two floating around the list, but currently no
> >> resolution on the argument it created.
> >>
> >> https://github.com/xenserver/xen-4.5.pg/blob/master/master/unknown-cacheabilit
> >>  
> >> y.patch
> >> is the XenServer fix.
> > Now that's surely wrong
> 
> Right or wrong, this is (apparently; I have not checked) what Linux does.
> 
> >  - if anything, unknown should be treated as
> > UC (and quite likely specifically in a case like the one Olaf reports here,
> > as the offending memory range pretty likely is other than normal RAM).
> > What I'd accept as a patch would be the addition of a command line
> > option enforcing the mapping of such unknown cacheability areas with
> > a certain caching type (default then being UC).
> 
> If I can find some copious free time, I will see about making this happen.

I actually did cobble a patch like this, but it is based on Daniel's Multibootv2
so it won't apply cleany. See attached patchset with various 'work-arounds'.

Jan if you are OK with them (well the 'idea' behind them) I can refresh
it against staging and post them?

Attachment: 0001-EFI-early-Implement-noexit-to-not-ExitBootServices.patch
Description: Text document

Attachment: 0002-EFI-early-Implement-map-to-map-EfiBootServicesData-a.patch
Description: Text document

Attachment: 0003-efi-Implement-efi-attr-uc-1-Xen-command-line-to-map-.patch
Description: Text document

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