> -----Original Message-----
> From: Julien Grall <jul...@xen.org>
> Sent: Tuesday, August 17, 2021 1:44 AM
> To: Penny Zheng <penny.zh...@arm.com>; xen-devel@lists.xenproject.org;
> sstabell...@kernel.org
> Cc: Bertrand Marquis <bertrand.marq...@arm.com>; Wei Chen
> <wei.c...@arm.com>; nd <n...@arm.com>
> Subject: Re: [PATCH V4 08/10] xen/arm: introduce acquire_staticmem_pages
> and acquire_domstatic_pages
>
>
>
> On 16/08/2021 07:43, Penny Zheng wrote:
> > Hi Julien,
>
> Hi,
>
> >>> +{
> >>> + bool need_tlbflush = false;
> >>> + uint32_t tlbflush_timestamp = 0;
> >>> + unsigned long i;
> >>> + struct page_info *pg;
> >>> +
> >>> + /* For now, it only supports pre-configured static memory. */
> >>
> >> This comment doesn't seem to match the check below.
> >>
> >>> + if ( !mfn_valid(smfn) || !nr_mfns )
> >>
> >> This check only guarantees that there will be a page for the first MFN.
> >> Shouldn't we also check for the other MFNs?
> >>
> >
> > Hmm, Do you think that it should be all checked, the whole range, [smfn,
> smfn + nr_mfns).
> > Since it is in linear growth, maybe adding another check of "!mfn_valid(smfn
> + nr_mfns - 1)"
> > is enough?
>
> The only requirement for Xen is to provide a valid struct page for each RAM
> page. So checking the first and end page may not be sufficient if there is a
> hole
> in the middle.
>
> My point here is either:
> - we trust the callers so we remove the mfn_valid() check
> - we don't trust the callers so we check the MFN is valid for every page
>
> My preference is the latter, the more if we plan to us the helper after boot
> in
> the future. An possible compromise is to add a comment that this function
> needs to be reworked if used outside of boot.
>
Ok. I'll do the whole range check and add the comments.
> Cheers,
>
>
> --
> Julien Grall
