Re: [Xen-devel] crash in efi_runtime_call

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 17/04/15 14:40, Konrad Rzeszutek Wilk wrote:
> 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?

I was planning to make one efi= command line option along the
psr/ept/iommu line, rather than having a large number of top-level
options (and folding our one efi-rs option into it).

But otherwise, that sounds like a plan.

~Andrew


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