[RFC PATCH 09/31] lmb: allow for resizing lmb regions
Ilias Apalodimas
ilias.apalodimas at linaro.org
Mon Jun 10 14:03:30 CEST 2024
Hi Sughosh
On Fri, 7 Jun 2024 at 21:54, 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.
Can you think of a memory region that needs to be protected from resizing?
I think we should design this a bit differently. For example, think
of someone loading a file in a memory region and then a subsystem
trying to resize its reserved memory overwriting that region. Instead
of this flag why don't we add
- A flag that indicates whether this region can be re-used (IOW
overwrites it), but only if the 'subsytem id' defined below matches
- a u32 that indicates the subsystem ID that initiated the transaction
-- e.g EFI, load command, U-Boot core .. etc
Resizing can be enabled unconditionally in that case as long as there
is enough space. The only requirement would be that the request comes
from the same subsystem that reserved the memory in the beginning
Thanks
/Ilias
>
> Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> ---
> include/lmb.h | 1 +
> lib/lmb.c | 120 ++++++++++++++++++++++++++++++++++++++++++++------
> 2 files changed, 107 insertions(+), 14 deletions(-)
>
> diff --git a/include/lmb.h b/include/lmb.h
> index 03bce2a50c..1d4cd255d2 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,
> };
>
> /**
> diff --git a/lib/lmb.c b/lib/lmb.c
> index de5a2cf23b..0a4f3d5bcd 100644
> --- a/lib/lmb.c
> +++ b/lib/lmb.c
> @@ -260,12 +260,88 @@ void lmb_add_memory(struct bd_info *bd)
> }
> }
>
> +static bool lmb_region_flags_match(struct lmb_region *rgn, unsigned long r1,
> + 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.
> + * 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)
> {
> unsigned long coalesced = 0;
> - long adjacent, i;
> + long ret, i;
>
> if (rgn->cnt == 0) {
> rgn->region[0].base = base;
> @@ -290,23 +366,32 @@ 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;
> + if (flags == LMB_NONE) {
> + ret = lmb_resize_regions(rgn, i, base, size,
> + flags);
> + if (ret < 0)
> + return -1;
> +
> + coalesced++;
> + break;
> + } else {
> + return -1;
> + }
> }
> }
>
> @@ -448,7 +533,7 @@ static phys_addr_t lmb_align_down(phys_addr_t addr, phys_size_t size)
> }
>
> static phys_addr_t __lmb_alloc_base(phys_size_t size, ulong align,
> - phys_addr_t max_addr)
> + phys_addr_t max_addr, enum lmb_flags flags)
> {
> long i, rgn;
> phys_addr_t base = 0;
> @@ -498,7 +583,7 @@ phys_addr_t lmb_alloc_base(phys_size_t size, ulong align, phys_addr_t max_addr)
> {
> phys_addr_t alloc;
>
> - alloc = __lmb_alloc_base(size, align, max_addr);
> + alloc = __lmb_alloc_base(size, align, max_addr, LMB_NONE);
>
> if (alloc == 0)
> printf("ERROR: Failed to allocate 0x%lx bytes below 0x%lx.\n",
> @@ -507,11 +592,8 @@ phys_addr_t lmb_alloc_base(phys_size_t size, ulong align, phys_addr_t max_addr)
> return alloc;
> }
>
> -/*
> - * Try to allocate a specific address range: must be in defined memory but not
> - * reserved
> - */
> -phys_addr_t lmb_alloc_addr(phys_addr_t base, phys_size_t size)
> +static phys_addr_t __lmb_alloc_addr(phys_addr_t base, phys_size_t size,
> + enum lmb_flags flags)
> {
> long rgn;
>
> @@ -526,13 +608,23 @@ phys_addr_t lmb_alloc_addr(phys_addr_t base, phys_size_t size)
> lmb.memory.region[rgn].size,
> base + size - 1, 1)) {
> /* ok, reserve the memory */
> - if (lmb_reserve(base, size) >= 0)
> + if (lmb_reserve_flags(base, size, flags) >= 0)
> return base;
> }
> }
> +
> return 0;
> }
>
> +/*
> + * Try to allocate a specific address range: must be in defined memory but not
> + * reserved
> + */
> +phys_addr_t lmb_alloc_addr(phys_addr_t base, phys_size_t size)
> +{
> + return __lmb_alloc_addr(base, size, LMB_NONE);
> +}
> +
> /* Return number of bytes from a given address that are free */
> phys_size_t lmb_get_free_size(phys_addr_t addr)
> {
> --
> 2.34.1
>
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