Re: [Xen-devel] [PATCH] x86/HVM: correct hvmemul_map_linear_addr() for multi-page case

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.09.18 at 13:51, <Paul.Durrant@xxxxxxxxxx> wrote:
>>  -----Original Message-----
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: 12 September 2018 10:10
>> To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
>> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Paul Durrant
>> <Paul.Durrant@xxxxxxxxxx>
>> Subject: [PATCH] x86/HVM: correct hvmemul_map_linear_addr() for multi-
>> page case
>> 
>> The function does two translations in one go for a single guest access.
>> Any failure of the first translation step (guest linear -> guest
>> physical), resulting in #PF, ought to take precedence over any failure
>> of the second step (guest physical -> host physical). Bail out of the
>> loop early solely when translation produces HVMTRANS_bad_linear_to_gfn,
>> and record the most relevant of perhaps multiple different errors
>> otherwise. (The choice of ZERO_BLOCK_PTR as sentinel is arbitrary.)
> 
> Could we have comment perhaps saying what the order of relevance of the 
> errors are? The logic in update_map_err() below is a little hard to follow.

Yeah, I was thinking about this meanwhile, and I'm also no longer
certain I've chosen the most sensible "ordering".

Jan



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