[{"id":3672510,"web_url":"http://patchwork.ozlabs.org/comment/3672510/","msgid":"","list_archive_url":null,"date":"2026-04-02T00:36:28","subject":"Re: [PATCH 1/6] lmb: add LMB_FDT for fdt reserved regions","submitter":{"id":88727,"url":"http://patchwork.ozlabs.org/api/people/88727/","name":"Randolph Sapp","email":"rs@ti.com"},"content":"On Wed Apr 1, 2026 at 7:14 PM CDT, rs wrote:\n> From: Randolph Sapp \n>\n> Add an LMB_FDT bit for fdt reserved regions, so we can reclaim them when\n> parsing a new device tree and properly warn people when a reservation\n> overlaps with an existing allocation.\n>\n> If we don't at least warn the user of these reservation failures,\n> there's a chance that this region could be freed and reallocated for\n> something important later.\n>\n> This useful warning mechanism was broken in:\n> 5a6aa7d5913 (\"boot: fdt: Handle already reserved memory in boot_fdt_reserve_region()\")\n>\n> Signed-off-by: Randolph Sapp \n> ---\n> boot/image-fdt.c | 5 ++++-\n> include/lmb.h | 7 +++++++\n> lib/lmb.c | 23 +++++++++++++++++++++++\n> 3 files changed, 34 insertions(+), 1 deletion(-)\n>\n> diff --git a/boot/image-fdt.c b/boot/image-fdt.c\n> index a3a4fb8b558..0f5857f24d2 100644\n> --- a/boot/image-fdt.c\n> +++ b/boot/image-fdt.c\n> @@ -73,6 +73,7 @@ static void boot_fdt_reserve_region(u64 addr, u64 size, u32 flags)\n> {\n> \tlong ret;\n> \tphys_addr_t rsv_addr;\n> +\tflags |= LMB_FDT;\n> \n> \trsv_addr = (phys_addr_t)addr;\n> \tret = lmb_alloc_mem(LMB_MEM_ALLOC_ADDR, 0, &rsv_addr, size, flags);\n> @@ -80,7 +81,7 @@ static void boot_fdt_reserve_region(u64 addr, u64 size, u32 flags)\n> \t\tdebug(\" reserving fdt memory region: addr=%llx size=%llx flags=%x\\n\",\n> \t\t (unsigned long long)addr,\n> \t\t (unsigned long long)size, flags);\n> -\t} else if (ret != -EEXIST && ret != -EINVAL) {\n> +\t} else if (ret != -EINVAL) {\n> \t\tputs(\"ERROR: reserving fdt memory region failed \");\n> \t\tprintf(\"(addr=%llx size=%llx flags=%x)\\n\",\n> \t\t (unsigned long long)addr,\n> @@ -108,6 +109,8 @@ void boot_fdt_add_mem_rsv_regions(void *fdt_blob)\n> \tif (fdt_check_header(fdt_blob) != 0)\n> \t\treturn;\n> \n> +\tlmb_free_fdt_regions();\n> +\n> \t/* process memreserve sections */\n> \ttotal = fdt_num_mem_rsv(fdt_blob);\n> \tfor (i = 0; i < total; i++) {\n> diff --git a/include/lmb.h b/include/lmb.h\n> index 5d5f037ccb9..1b59a63f61d 100644\n> --- a/include/lmb.h\n> +++ b/include/lmb.h\n> @@ -25,11 +25,13 @@\n> * %LMB_NOMAP: Don't add to MMU configuration\n> * %LMB_NOOVERWRITE: The memory region cannot be overwritten/re-reserved\n> * %LMB_NONOTIFY: Do not notify other modules of changes to this memory region\n> + * %LMB_FDT: A FDT reserved region that can be reclaimed if the FDT changes\n> */\n> #define LMB_NONE 0\n> #define LMB_NOMAP BIT(1)\n> #define LMB_NOOVERWRITE BIT(2)\n> #define LMB_NONOTIFY BIT(3)\n> +#define LMB_FDT BIT(4)\n> \n> /**\n> * enum lmb_mem_type - type of memory allocation request\n> @@ -215,6 +217,11 @@ phys_addr_t io_lmb_alloc(struct lmb *io_lmb, phys_size_t size, ulong align);\n> */\n> long io_lmb_free(struct lmb *io_lmb, phys_addr_t base, phys_size_t size);\n> \n> +/**\n> + * lmb_free_fdt_regions() - Reclaim all LMB_FDT tagged reserved regions\n> + */\n> +void lmb_free_fdt_regions(void);\n> +\n> #endif /* __KERNEL__ */\n> \n> #endif /* _LINUX_LMB_H */\n> diff --git a/lib/lmb.c b/lib/lmb.c\n> index e2d9fe86c14..542bb11dcf5 100644\n> --- a/lib/lmb.c\n> +++ b/lib/lmb.c\n> @@ -669,6 +669,29 @@ long lmb_free(phys_addr_t base, phys_size_t size, u32 flags)\n> \treturn lmb_map_update_notify(base, size, LMB_MAP_OP_FREE, flags);\n> }\n> \n> +void lmb_free_fdt_regions(void)\n> +{\n> +\tstruct alist *lmb_rgn_lst = &lmb.used_mem;\n> +\tstruct lmb_region *rgn = lmb_rgn_lst->data;\n> +\tlong ret;\n> +\n> +\tfor (int i = 0; i < lmb_rgn_lst->count; i++) {\n> +\t\tphys_addr_t base = rgn[i].base;\n> +\t\tphys_size_t size = rgn[i].size;\n> +\t\tu32 flags = rgn[i].flags;\n> +\n> +\t\tif (flags & LMB_FDT) {\n> +\t\t\tret = lmb_free(base, size, flags);\n> +\t\t\tif (ret < 0) {\n> +\t\t\t\tprintf(\"Unable to free FDT memory at 0x%08lx\",\n> +\t\t\t\t (ulong)base);\n> +\t\t\t\tcontinue;\n> +\t\t\t}\n> +\t\t\ti--;\n> +\t\t}\n> +\t}\n> +}\n> +\n> static int _lmb_alloc_base(phys_size_t size, ulong align,\n> \t\t\t phys_addr_t *addr, u32 flags)\n> {\n\nUgh. Looking at that loop in lmb_free_fdt_regions more I really should have\nwritten it differently to avoid the additional increments and decrements. I'll\nfix that in v2.","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=ti.com header.i=@ti.com header.a=rsa-sha256\n header.s=selector1 header.b=sq8CE0fD;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.denx.de\n (client-ip=85.214.62.61; helo=phobos.denx.de;\n envelope-from=u-boot-bounces@lists.denx.de; receiver=patchwork.ozlabs.org)","phobos.denx.de;\n dmarc=pass (p=quarantine dis=none) header.from=ti.com","phobos.denx.de;\n spf=pass smtp.mailfrom=u-boot-bounces@lists.denx.de","phobos.denx.de;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=ti.com header.i=@ti.com header.b=\"sq8CE0fD\";\n\tdkim-atps=neutral","phobos.denx.de;\n dmarc=pass (p=quarantine dis=none) header.from=ti.com","phobos.denx.de; spf=pass smtp.mailfrom=rs@ti.com"],"Received":["from phobos.denx.de (phobos.denx.de [85.214.62.61])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fmNG30sw3z1yFv\n\tfor ; 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