Re: [Xen-devel] [PATCH v3 3/3] xen: rework paging_log_dirty_op to work with hvm guests

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

Hello,

I think I've fixed the rest of the comments, this one however is not
easy to deal with.

El 14/04/15 a les 14.14, Jan Beulich ha escrit:
>>>> On 10.04.15 at 19:29, <roger.pau@xxxxxxxxxx> wrote:
>> +                    BUG_ON(((pages >> 3) % PAGE_SIZE) + bytes > PAGE_SIZE);
> 
> I don't seem to be able to spot the original for this one. If there
> was none, please make this an ASSERT() instead.

Yes, there's no previous BUG_ON because this was not a problem in the
past, since we could write to any position on dirty_bitmap, but that's
not the case any more. Since we only have one page mapped at a time we
need to make sure that what we are about to write doesn't cross a page
boundary.

I understand this is not an ideal solution, but AFAICT there's no easy
way to deal with writes that expand over a page boundary.

Roger.

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