linux-kernel - Re: [PATCH v2 1/1] of: fdt: Scan /memreserve/ last

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Date:   Mon, 10 Apr 2023 10:58:10 -0400
From:   Lucas Tanure <tanure@...ux.com>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Frank Rowand <frowand.list@...il.com>,
        Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, jbrunet@...libre.com,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        martin.blumenstingl@...glemail.com, narmstrong@...libre.com,
        stefan@...er.ch
Subject: Re: [PATCH v2 1/1] of: fdt: Scan /memreserve/ last

On Mon, Apr 10, 2023 at 8:52 AM Rob Herring <robh+dt@...nel.org> wrote:
>
> On Mon, Apr 10, 2023 at 7:00 AM Lucas Tanure <tanure@...ux.com> wrote:
> >
> > Change the order of scanning /memreserve/ and /reserved-memory node.
> > /reserved-memory node should go first, as it has a more updated
> > description of the memory regions and it can apply flags, like nomap.
> > Also, /memreserve/ should avoid reserving regions described in
> > /reserved-memory node.
>
> Like I said on v1, I think doing this has a high chance of causing
> regressions on other platforms. It should probably not go to stable
> for some time after a kernel release.
>
> > Signed-off-by: Lucas Tanure <tanure@...ux.com>
> > ---
> >  drivers/of/fdt.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > index d1a68b6d03b3..26e608d8025d 100644
> > --- a/drivers/of/fdt.c
> > +++ b/drivers/of/fdt.c
> > @@ -635,16 +635,21 @@ void __init early_init_fdt_scan_reserved_mem(void)
> >         if (!initial_boot_params)
> >                 return;
> >
> > +       fdt_scan_reserved_mem();
> > +       fdt_reserve_elfcorehdr();
> > +
> >         /* Process header /memreserve/ fields */
> >         for (n = 0; ; n++) {
> >                 fdt_get_mem_rsv(initial_boot_params, n, &base, &size);
> >                 if (!size)
> >                         break;
> > +               if (memblock_overlaps_region(&memblock.memory, base, size) &&
> > +                   memblock_is_region_reserved(base, size))
>
> Just to make sure, a partial overlap will still get reserved?
A partial overlap will get reserved if not already reserved by the
/reserved-memory node.
>
> > +                       break;
>
> Shouldn't we continue to the next entry rather than stopping.
Yes, my mistake; I will send v3.
>
> > +
> >                 memblock_reserve(base, size);
> >         }
> >
> > -       fdt_scan_reserved_mem();
> > -       fdt_reserve_elfcorehdr();
> >         fdt_init_reserved_mem();
> >  }
> >
> > --
> > 2.40.0
> >