Re: [Xen-devel] an assertion triggered when running Xen on a HSW desktop

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.01.19 at 10:44, <Paul.Durrant@xxxxxxxxxx> wrote:
>>  -----Original Message-----
> [snip]
>> >> (XEN) Xen call trace:
>> >> (XEN)    [<ffff82d08025ccbc>] iommu_map+0xba/0x176
>> >> (XEN)    [<ffff82d0804182d8>] iommu_hwdom_init+0xef/0x220
>> >> (XEN)    [<ffff82d08043716c>] dom0_construct_pvh+0x189/0x129e
>> >> (XEN)    [<ffff82d08043e53c>] construct_dom0+0xd4/0xb14
>> >> (XEN)    [<ffff82d08042d8ef>] __start_xen+0x2710/0x2830
>> >> (XEN)    [<ffff82d0802000f3>] __high_start+0x53/0x55
>> >> (XEN)
>> >> (XEN)
>> >> (XEN) ****************************************
>> >> (XEN) Panic on CPU 0:
>> >> (XEN) Assertion 'IS_ALIGNED(dfn_x(dfn), (1ul << page_order))' failed at
>> iommu.c:323
>> >> (XEN) ****************************************
>> >
>> >Oh, this was added by Paul quite recently. You seem to be using a
>> >rather old commit (a5b0eb3636), is there any reason for using such an
>> >old baseline?
>> 
>> I was using the master branch. Your patch below did fix this issue.
> 
> Given this failure and the fact that valid orders differ between different 
> architectures, I propose we change the argument to the iommu_map/unmap 
> wrapper functions from an order to a count, thus making it clear that there 
> is no alignment restriction.

But the whole idea is for there to be an alignment restriction, such
that it is easy to determine whether large page mappings can be
used to satisfy the request. What's the exact case where a caller
absolutely has to pass in a mis-aligned (dfn,size) tuple?

Jan



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