Re: [Xen-devel] [PATCH v5 01/16] x86/mm: skip incrementing mfn if it is not a valid mfn

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 15/03/18 07:52, Jan Beulich wrote:
>>>> On 14.03.18 at 19:31, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 14/03/18 18:19, julien.grall@xxxxxxx wrote:
>>> From: Wei Liu <wei.liu2@xxxxxxxxxx>
>>>
>>> The function is called to fill in page table entries in
>>> populate_pt_range. Skip incrementing mfn if it is invalid.
>>>
>>> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
>> Remind me what the purpose of this patch is?
> This is in preparation to switch callers to pass INVALID_MFN
> instead of zero for non-present mappings. The incrementing
> from zero was wrong here already (but couldn't be as easily
> avoided, to not cause problems with possible legitimate uses of
> MFN 0), but incrementing (and wrapping) from INVALID_MFN is
> (imo) even worse, which is why I had asked the conversion to
> INVALID_MFN to not be done without this change.

Yes.  My reply was a (clearly too) thinly veiled hint that a sentence to
this effect should be in the commit message.

The code itself is fine.

~Andrew

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