RE: [Xen-devel] Xen 4.0.0-rc7 problem/hang with vt-d DMAR parsing

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> "Cui, Dexuan" <dexuan.cui@xxxxxxxxx> 24.03.10 02:52 >>>
>Pasi K?rkk?inen wrote:
>> Hmm.. wondering if the patch Jan just sent will help with that.
>> Sounds like it might help :)
>I guess Jan's patch helps here in a very interesting way:

I think reference was to a patch I sent yesterday, which I don't think
would help here (as the box would have to crash for it to help).

>I suspect your BIOS doesn't construct the DMAR properly, e.g., in 
>acpi_parse_dmar(),  entry_header->length is always 0, so xen'll hang in the 
>while loop and continue printing the "dmaru->address = 0" message when 
>iommu=verbose.

Surely entry_header->length == 0 (or really
entry_header->length < sizeof(struct acpi_table_XXX)) should be
considered invalid, and hence get checked for? Linux at least has
a check against zero here...

>Without verbose message outputing, the loop runs even faster and in 
>acpi_parse_one_drhd(),  xmalloc(struct acpi_drhd_unit) would NULL in a short 
>periof of time and hence VT-d is got disabled... :-)

Why would you expect xmalloc() to fail soon? This is only to be expected
on a 32-bit system (which I doubt this one is).

Jan


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