[RFC PATCH v2 12/48] lmb: allow for resizing lmb regions

Sughosh Ganu sughosh.ganu at linaro.org
Mon Jul 15 11:27:20 CEST 2024


hi Simon,

On Sat, 13 Jul 2024 at 20:45, Simon Glass <sjg at chromium.org> wrote:
>
> Hi Sughosh,
>
> On Thu, 4 Jul 2024 at 08:36, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
> >
> > Allow for resizing of LMB regions if the region attributes match. The
> > current code returns a failure status on detecting an overlapping
> > address. This worked up until now since the LMB calls were not
> > persistent and global -- the LMB memory map was specific and private
> > to a given caller of the LMB API's.
> >
> > With the change in the LMB code to make the LMB reservations
> > persistent, there needs to be a check on whether the memory region can
> > be resized, and then do it if so. To distinguish between memory that
> > cannot be resized, add a new flag, LMB_NOOVERWRITE. Reserving a region
> > of memory with this attribute would indicate that the region cannot be
> > resized.
> >
> > Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> > ---
> > Changes since V1:
> > * Do the check for the region flags in lmb_resize_regions() and
> >   lmb_merge_overlap_regions() to decide on merging the overlapping
> >   regions.
> >
> >  include/lmb.h |   1 +
> >  lib/lmb.c     | 116 ++++++++++++++++++++++++++++++++++++++++++++------
> >  2 files changed, 103 insertions(+), 14 deletions(-)
> >
> > diff --git a/include/lmb.h b/include/lmb.h
> > index 069c6af2a3..99fcf5781f 100644
> > --- a/include/lmb.h
> > +++ b/include/lmb.h
> > @@ -20,6 +20,7 @@
> >  enum lmb_flags {
> >         LMB_NONE                = 0x0,
> >         LMB_NOMAP               = 0x4,
> > +       LMB_NOOVERWRITE         = 0x8,
>
> How about LMB_PERSIST ?

Isn't LMB_NOOVERWRITE more suitable here ? I mean this is indicating
that the said region of memory is not to be re-used/re-requested.

>
> These could be adjusted to use BIT()

I am changing these to use the BIT macro in a subsequent commit.

>
> >  };
> >
> >  /**
> > diff --git a/lib/lmb.c b/lib/lmb.c
> > index 0d01e58a46..80945e3cae 100644
> > --- a/lib/lmb.c
> > +++ b/lib/lmb.c
> > @@ -230,12 +230,88 @@ void lmb_init_and_reserve_range(phys_addr_t base, phys_size_t size,
> >         lmb_reserve_common(fdt_blob);
> >  }
> >
> > +static bool lmb_region_flags_match(struct lmb_region *rgn, unsigned long r1,
>
> At some point the index should change to an int (or uint), rather than
> unsigned long. I had a series that did that, but it died.
>
> > +                                  enum lmb_flags flags)
> > +{
> > +       return rgn->region[r1].flags == flags;
> > +}
> > +
> > +static long lmb_merge_overlap_regions(struct lmb_region *rgn, unsigned long i,
> > +                                     phys_addr_t base, phys_size_t size,
> > +                                     enum lmb_flags flags)
> > +{
> > +       phys_size_t rgnsize;
> > +       unsigned long rgn_cnt, idx;
> > +       phys_addr_t rgnbase, rgnend;
> > +       phys_addr_t mergebase, mergeend;
> > +
> > +       rgn_cnt = 0;
> > +       idx = i;
> > +       /*
> > +        * First thing to do is to identify how many regions does
> > +        * the requested region overlap.
>
> how many regions the requested region overlaps

Okay

>
> > +        * If the flags match, combine all these overlapping
> > +        * regions into a single region, and remove the merged
> > +        * regions.
> > +        */
> > +       while (idx < rgn->cnt - 1) {
> > +               rgnbase = rgn->region[idx].base;
> > +               rgnsize = rgn->region[idx].size;
> > +
> > +               if (lmb_addrs_overlap(base, size, rgnbase,
> > +                                     rgnsize)) {
> > +                       if (!lmb_region_flags_match(rgn, idx, flags))
> > +                               return -1;
> > +                       rgn_cnt++;
> > +                       idx++;
> > +               }
> > +       }
> > +
> > +       /* The merged region's base and size */
> > +       rgnbase = rgn->region[i].base;
> > +       mergebase = min(base, rgnbase);
> > +       rgnend = rgn->region[idx].base + rgn->region[idx].size;
> > +       mergeend = max(rgnend, (base + size));
> > +
> > +       rgn->region[i].base = mergebase;
> > +       rgn->region[i].size = mergeend - mergebase;
> > +
> > +       /* Now remove the merged regions */
> > +       while (--rgn_cnt)
> > +               lmb_remove_region(rgn, i + 1);
> > +
> > +       return 0;
> > +}
> > +
> > +static long lmb_resize_regions(struct lmb_region *rgn, unsigned long i,
> > +                              phys_addr_t base, phys_size_t size,
> > +                              enum lmb_flags flags)
> > +{
> > +       long ret = 0;
> > +       phys_addr_t rgnend;
> > +
> > +       if (i == rgn->cnt - 1 ||
> > +               base + size < rgn->region[i + 1].base) {
> > +               if (!lmb_region_flags_match(rgn, i, flags))
> > +                       return -1;
> > +
> > +               rgnend = rgn->region[i].base + rgn->region[i].size;
> > +               rgn->region[i].base = min(base, rgn->region[i].base);
> > +               rgnend = max(base + size, rgnend);
> > +               rgn->region[i].size = rgnend - rgn->region[i].base;
> > +       } else {
> > +               ret = lmb_merge_overlap_regions(rgn, i, base, size, flags);
> > +       }
> > +
> > +       return ret;
> > +}
> > +
> >  /* This routine called with relocation disabled. */
> >  static long lmb_add_region_flags(struct lmb_region *rgn, phys_addr_t base,
> >                                  phys_size_t size, enum lmb_flags flags)
>
> This could really use a function comment

Okay

-sughosh

>
> >  {
> >         unsigned long coalesced = 0;
> > -       long adjacent, i;
> > +       long ret, i;
> >
> >         if (rgn->cnt == 0) {
> >                 rgn->region[0].base = base;
> > @@ -260,23 +336,28 @@ static long lmb_add_region_flags(struct lmb_region *rgn, phys_addr_t base,
> >                                 return -1; /* regions with new flags */
> >                 }
> >
> > -               adjacent = lmb_addrs_adjacent(base, size, rgnbase, rgnsize);
> > -               if (adjacent > 0) {
> > +               ret = lmb_addrs_adjacent(base, size, rgnbase, rgnsize);
> > +               if (ret > 0) {
> >                         if (flags != rgnflags)
> >                                 break;
> >                         rgn->region[i].base -= size;
> >                         rgn->region[i].size += size;
> >                         coalesced++;
> >                         break;
> > -               } else if (adjacent < 0) {
> > +               } else if (ret < 0) {
> >                         if (flags != rgnflags)
> >                                 break;
> >                         rgn->region[i].size += size;
> >                         coalesced++;
> >                         break;
> >                 } else if (lmb_addrs_overlap(base, size, rgnbase, rgnsize)) {
> > -                       /* regions overlap */
> > -                       return -1;
> > +                       ret = lmb_resize_regions(rgn, i, base, size,
> > +                                                flags);
> > +                       if (ret < 0)
> > +                               return -1;
> > +
> > +                       coalesced++;
> > +                       break;
> >                 }
> >         }
> >
> > @@ -418,7 +499,7 @@ static phys_addr_t lmb_align_down(phys_addr_t addr, phys_size_t size)
> >  }
> >
>
> Regards,
> Simon


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