[PATCH 0/3] efi: Simply DT handoff from stub to kernel

[PATCH 0/3] efi: Simply DT handoff from stub to kernel

[Ard Biesheuvel]

Currently, 4 separate DT properties are used as an internal ABI to hand
over the EFI memory map from the EFI stub to the kernel proper.

This information is redundant, as the same information is already made
available via a EFI configuration table.

So replace those 4 DT properties with a single one that carries the
address of this config table, and make it optional, so that it can be
omitted in cases where the kernel is able to locate the table directly
via its GUID.

Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: loongarch@lists.linux.dev

Ard Biesheuvel (3):
  efi: Turn boot memmap handling into shared code
  efi: Pass EFI boot memmap struct address to core kernel
  efi: Make the 'linux,uefi-boot-memmap' DT property optional

 Documentation/arch/arm/uefi.rst    | 10 +--
 arch/loongarch/kernel/efi.c        | 10 +--
 drivers/firmware/efi/efi.c         |  4 +
 drivers/firmware/efi/fdtparams.c   | 77 ++++++++++++++++++--
 drivers/firmware/efi/libstub/fdt.c | 40 +---------
 include/linux/efi.h                |  3 +
 6 files changed, 84 insertions(+), 60 deletions(-)

-- 
2.47.3

[PATCH 1/3] efi: Turn boot memmap handling into shared code

[Ard Biesheuvel]

Move the handling of the boot memmap config table from loongarch
specific code to code that is shared between all architectures that
select EFI_GENERIC_STUB (all EFI archs except x86).

This will be used in a subsequent patch to replace the clunky FDT based
passing of the memmap parameters.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/loongarch/kernel/efi.c | 10 ++++------
 drivers/firmware/efi/efi.c  |  4 ++++
 include/linux/efi.h         |  3 +++
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/arch/loongarch/kernel/efi.c b/arch/loongarch/kernel/efi.c
index 69dd83f8082f..089378856bab 100644
--- a/arch/loongarch/kernel/efi.c
+++ b/arch/loongarch/kernel/efi.c
@@ -28,12 +28,10 @@
 static unsigned long efi_nr_tables;
 static unsigned long efi_config_table;
 
-static unsigned long __initdata boot_memmap = EFI_INVALID_TABLE_ADDR;
 static unsigned long __initdata fdt_pointer = EFI_INVALID_TABLE_ADDR;
 
 static efi_system_table_t *efi_systab;
 static efi_config_table_type_t arch_tables[] __initdata = {
-	{LINUX_EFI_BOOT_MEMMAP_GUID,	&boot_memmap,	"MEMMAP" },
 	{DEVICE_TREE_GUID,		&fdt_pointer,	"FDTPTR" },
 	{},
 };
@@ -132,14 +130,14 @@ void __init efi_init(void)
 	if (IS_ENABLED(CONFIG_EFI_EARLYCON) || IS_ENABLED(CONFIG_SYSFB))
 		init_primary_display();
 
-	if (boot_memmap == EFI_INVALID_TABLE_ADDR)
+	if (efi.boot_memmap == EFI_INVALID_TABLE_ADDR)
 		return;
 
-	tbl = early_memremap_ro(boot_memmap, sizeof(*tbl));
+	tbl = early_memremap_ro(efi.boot_memmap, sizeof(*tbl));
 	if (tbl) {
 		struct efi_memory_map_data data;
 
-		data.phys_map		= boot_memmap + sizeof(*tbl);
+		data.phys_map		= efi.boot_memmap + sizeof(*tbl);
 		data.size		= tbl->map_size;
 		data.desc_size		= tbl->desc_size;
 		data.desc_version	= tbl->desc_ver;
@@ -156,7 +154,7 @@ void __init efi_init(void)
 		 * Also, set the EFI_PRESERVE_BS_REGIONS flag to indicate that
 		 * critical boot services code/data regions like this are preserved.
 		 */
-		memblock_reserve((phys_addr_t)boot_memmap, sizeof(*tbl) + data.size);
+		memblock_reserve((phys_addr_t)efi.boot_memmap, sizeof(*tbl) + data.size);
 		set_bit(EFI_PRESERVE_BS_REGIONS, &efi.flags);
 
 		early_memunmap(tbl, sizeof(*tbl));
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 0327a39d31fa..d33760d6a527 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -55,6 +55,9 @@ struct efi __read_mostly efi = {
 #ifdef CONFIG_UNACCEPTED_MEMORY
 	.unaccepted		= EFI_INVALID_TABLE_ADDR,
 #endif
+#ifdef CONFIG_EFI_GENERIC_STUB
+	.boot_memmap		= EFI_INVALID_TABLE_ADDR,
+#endif
 };
 EXPORT_SYMBOL(efi);
 
@@ -647,6 +650,7 @@ static const efi_config_table_type_t common_tables[] __initconst = {
 	{LINUX_EFI_UNACCEPTED_MEM_TABLE_GUID,	&efi.unaccepted,	"Unaccepted"	},
 #endif
 #ifdef CONFIG_EFI_GENERIC_STUB
+	{LINUX_EFI_BOOT_MEMMAP_GUID,		&efi.boot_memmap,	"MEMMAP"	},
 	{LINUX_EFI_PRIMARY_DISPLAY_TABLE_GUID,	&primary_display_table			},
 #endif
 	{},
diff --git a/include/linux/efi.h b/include/linux/efi.h
index aa15ff88539b..bc1cd005ca0f 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -650,6 +650,9 @@ extern struct efi {
 	unsigned long			mokvar_table;		/* MOK variable config table */
 	unsigned long			coco_secret;		/* Confidential computing secret table */
 	unsigned long			unaccepted;		/* Unaccepted memory table */
+#ifdef CONFIG_EFI_GENERIC_STUB
+	unsigned long			boot_memmap;		/* The EFI memory map captured by the stub */
+#endif
 
 	efi_get_time_t			*get_time;
 	efi_set_time_t			*set_time;
-- 
2.47.3

[PATCH 2/3] efi: Pass EFI boot memmap struct address to core kernel

[Ard Biesheuvel]

The EFI stub already passes a struct efi_boot_memmap populated with the
information of the EFI memory map as a configuration table, and so
passing the physical address, size, descriptor size and descriptor
version via 4 different DT properties is kind of redundant.

Instead, pass the physical address of this struct in memory so that the
kernel can just retrieve the values directly.

Unfortunately, the scheme with four separate properties is boot ABI for
Xen, and so this needs to remain supported. But for the EFI stub itself,
this is just an internal ABI that can be modified.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 Documentation/arch/arm/uefi.rst    | 10 +----
 drivers/firmware/efi/fdtparams.c   | 39 ++++++++++++++++---
 drivers/firmware/efi/libstub/fdt.c | 40 ++------------------
 3 files changed, 37 insertions(+), 52 deletions(-)

diff --git a/Documentation/arch/arm/uefi.rst b/Documentation/arch/arm/uefi.rst
index 2b7ad9bd7cd2..c19cf3720f27 100644
--- a/Documentation/arch/arm/uefi.rst
+++ b/Documentation/arch/arm/uefi.rst
@@ -54,17 +54,9 @@ Name                        Type     Description
 ==========================  ======   ===========================================
 linux,uefi-system-table     64-bit   Physical address of the UEFI System Table.
 
-linux,uefi-mmap-start       64-bit   Physical address of the UEFI memory map,
+linux,uefi-boot-memmap      64-bit   Physical address of a struct efi_boot_memmap
                                      populated by the UEFI GetMemoryMap() call.
 
-linux,uefi-mmap-size        32-bit   Size in bytes of the UEFI memory map
-                                     pointed to in previous entry.
-
-linux,uefi-mmap-desc-size   32-bit   Size in bytes of each entry in the UEFI
-                                     memory map.
-
-linux,uefi-mmap-desc-ver    32-bit   Version of the mmap descriptor format.
-
 kaslr-seed                  64-bit   Entropy used to randomize the kernel image
                                      base address location.
 
diff --git a/drivers/firmware/efi/fdtparams.c b/drivers/firmware/efi/fdtparams.c
index b815d2a754ee..a54a76a6aaeb 100644
--- a/drivers/firmware/efi/fdtparams.c
+++ b/drivers/firmware/efi/fdtparams.c
@@ -10,22 +10,30 @@
 
 #include <linux/unaligned.h>
 
+#include <asm/early_ioremap.h>
+
 enum {
 	SYSTAB,
+	MEMMAP,
+#ifdef CONFIG_XEN
 	MMBASE,
 	MMSIZE,
 	DCSIZE,
 	DCVERS,
+#endif
 
 	PARAMCOUNT
 };
 
 static __initconst const char name[][22] = {
 	[SYSTAB] = "System Table         ",
+	[MEMMAP] = "Boot Memory Map      ",
+#ifdef CONFIG_XEN
 	[MMBASE] = "MemMap Address       ",
 	[MMSIZE] = "MemMap Size          ",
 	[DCSIZE] = "MemMap Desc. Size    ",
 	[DCVERS] = "MemMap Desc. Version ",
+#endif
 };
 
 static __initconst const struct {
@@ -49,10 +57,7 @@ static __initconst const struct {
 		.path = "/chosen",
 		.params = {	//  <-----------26----------->
 			[SYSTAB] = "linux,uefi-system-table",
-			[MMBASE] = "linux,uefi-mmap-start",
-			[MMSIZE] = "linux,uefi-mmap-size",
-			[DCSIZE] = "linux,uefi-mmap-desc-size",
-			[DCVERS] = "linux,uefi-mmap-desc-ver",
+			[MEMMAP] = "linux,uefi-boot-memmap",
 		}
 	}
 };
@@ -84,17 +89,20 @@ static int __init efi_get_fdt_prop(const void *fdt, int node, const char *pname,
 u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
 {
 	const void *fdt = initial_boot_params;
-	unsigned long systab;
+	unsigned long systab, memmap;
 	int i, j, node;
 	struct {
 		void	*var;
 		int	size;
 	} target[] = {
 		[SYSTAB] = { &systab,		sizeof(systab) },
+		[MEMMAP] = { &memmap,		sizeof(memmap) },
+#ifdef CONFIG_XEN
 		[MMBASE] = { &mm->phys_map,	sizeof(mm->phys_map) },
 		[MMSIZE] = { &mm->size,		sizeof(mm->size) },
 		[DCSIZE] = { &mm->desc_size,	sizeof(mm->desc_size) },
 		[DCVERS] = { &mm->desc_version,	sizeof(mm->desc_version) },
+#endif
 	};
 
 	BUILD_BUG_ON(ARRAY_SIZE(target) != ARRAY_SIZE(name));
@@ -115,6 +123,9 @@ u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
 		for (j = 0; j < ARRAY_SIZE(target); j++) {
 			const char *pname = dt_params[i].params[j];
 
+			if (pname[0] == '\0')
+				continue;
+
 			if (!efi_get_fdt_prop(fdt, node, pname, name[j],
 					      target[j].var, target[j].size))
 				continue;
@@ -123,8 +134,24 @@ u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
 			pr_err("Can't find property '%s' in DT!\n", pname);
 			return 0;
 		}
-		if (dt_params[i].paravirt)
+		if (IS_ENABLED(CONFIG_XEN) && dt_params[i].paravirt) {
 			set_bit(EFI_PARAVIRT, &efi.flags);
+		} else {
+			struct efi_boot_memmap *bm;
+
+			bm = early_memremap_ro(memmap, sizeof(*bm));
+			if (!bm) {
+				pr_err("Cannot remap EFI boot memory map\n");
+				return 0;
+			}
+
+			mm->phys_map		= memmap + sizeof(*bm);
+			mm->size		= bm->map_size;
+			mm->desc_size		= bm->desc_size;
+			mm->desc_version	= bm->desc_ver;
+
+			early_memunmap(bm, sizeof(*bm));
+		}
 		return systab;
 	}
 notfound:
diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
index 23b3543d3041..417b1344bdd8 100644
--- a/drivers/firmware/efi/libstub/fdt.c
+++ b/drivers/firmware/efi/libstub/fdt.c
@@ -32,7 +32,6 @@ static efi_status_t update_fdt(void *orig_fdt, unsigned long orig_fdt_size,
 {
 	int node, num_rsv;
 	int status;
-	fdt32_t fdt_val32;
 	fdt64_t fdt_val64;
 
 	/* Do some checks on provided FDT, if it exists: */
@@ -102,21 +101,7 @@ static efi_status_t update_fdt(void *orig_fdt, unsigned long orig_fdt_size,
 
 	fdt_val64 = cpu_to_fdt64(U64_MAX); /* placeholder */
 
-	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-start", fdt_val64);
-	if (status)
-		goto fdt_set_fail;
-
-	fdt_val32 = cpu_to_fdt32(U32_MAX); /* placeholder */
-
-	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-size", fdt_val32);
-	if (status)
-		goto fdt_set_fail;
-
-	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-desc-size", fdt_val32);
-	if (status)
-		goto fdt_set_fail;
-
-	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-desc-ver", fdt_val32);
+	status = fdt_setprop_var(fdt, node, "linux,uefi-boot-memmap", fdt_val64);
 	if (status)
 		goto fdt_set_fail;
 
@@ -148,33 +133,14 @@ static efi_status_t update_fdt_memmap(void *fdt, struct efi_boot_memmap *map)
 {
 	int node = fdt_path_offset(fdt, "/chosen");
 	fdt64_t fdt_val64;
-	fdt32_t fdt_val32;
 	int err;
 
 	if (node < 0)
 		return EFI_LOAD_ERROR;
 
-	fdt_val64 = cpu_to_fdt64((unsigned long)map->map);
-
-	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-start", fdt_val64);
-	if (err)
-		return EFI_LOAD_ERROR;
-
-	fdt_val32 = cpu_to_fdt32(map->map_size);
-
-	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-size", fdt_val32);
-	if (err)
-		return EFI_LOAD_ERROR;
-
-	fdt_val32 = cpu_to_fdt32(map->desc_size);
-
-	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-desc-size", fdt_val32);
-	if (err)
-		return EFI_LOAD_ERROR;
-
-	fdt_val32 = cpu_to_fdt32(map->desc_ver);
+	fdt_val64 = cpu_to_fdt64((unsigned long)map);
 
-	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-desc-ver", fdt_val32);
+	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-boot-memmap", fdt_val64);
 	if (err)
 		return EFI_LOAD_ERROR;
 
-- 
2.47.3

[PATCH 3/3] efi: Make the 'linux,uefi-boot-memmap' DT property optional

[Ard Biesheuvel]

The 'linux,uefi-boot-memmap DT property' is redundant in principle,
given that it carries a physical address that is also passed via a EFI
config table entry.

However, if SetVirtualAddressMap() has been called, the address of the
config table array has been translated to virtual, and so the memory map
is needed to translate it back to physical before it can be located.

This means that passing the linux,uefi-boot-memmap DT property is only
needed if SetVirtualAddressMap() has been called, which is a terrible
idea anyway, and if it has not been called, the config table array can
simply be parsed to look for LINUX_EFI_BOOT_MEMMAP_TABLE_GUID, and the
address taken from there.

So permit this, and make the boot memmap property optional.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 drivers/firmware/efi/fdtparams.c | 42 ++++++++++++++++++--
 1 file changed, 38 insertions(+), 4 deletions(-)

diff --git a/drivers/firmware/efi/fdtparams.c b/drivers/firmware/efi/fdtparams.c
index a54a76a6aaeb..89ffccf35fd7 100644
--- a/drivers/firmware/efi/fdtparams.c
+++ b/drivers/firmware/efi/fdtparams.c
@@ -89,14 +89,15 @@ static int __init efi_get_fdt_prop(const void *fdt, int node, const char *pname,
 u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
 {
 	const void *fdt = initial_boot_params;
-	unsigned long systab, memmap;
+	unsigned long systab, memmap = 0;
 	int i, j, node;
 	struct {
 		void	*var;
 		int	size;
+		int	optional;
 	} target[] = {
 		[SYSTAB] = { &systab,		sizeof(systab) },
-		[MEMMAP] = { &memmap,		sizeof(memmap) },
+		[MEMMAP] = { &memmap,		sizeof(memmap), 1 },
 #ifdef CONFIG_XEN
 		[MMBASE] = { &mm->phys_map,	sizeof(mm->phys_map) },
 		[MMSIZE] = { &mm->size,		sizeof(mm->size) },
@@ -131,14 +132,47 @@ u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
 				continue;
 			if (!j)
 				goto notfound;
-			pr_err("Can't find property '%s' in DT!\n", pname);
-			return 0;
+			if (!target[j].optional) {
+				pr_err("Can't find property '%s' in DT!\n", pname);
+				return 0;
+			}
 		}
 		if (IS_ENABLED(CONFIG_XEN) && dt_params[i].paravirt) {
 			set_bit(EFI_PARAVIRT, &efi.flags);
 		} else {
 			struct efi_boot_memmap *bm;
 
+			if (!memmap) {
+				unsigned long tables, nr_tables;
+				efi_system_table_t *st;
+				efi_config_table_t *tbl;
+
+				st = early_memremap_ro(systab, sizeof(*st));
+				if (!st) {
+					pr_err("Cannot remap EFI system table\n");
+					return 0;
+				}
+
+				tables		= st->tables;
+				nr_tables	= st->nr_tables;
+
+				early_memunmap(st, sizeof(*st));
+
+				tbl = early_memremap_ro(tables, sizeof(*tbl) * nr_tables);
+				if (!tbl) {
+					pr_err("Cannot remap EFI config table array\n");
+					return 0;
+				}
+
+				for (int i = 0; i < nr_tables; i++) {
+					if (!efi_guidcmp(tbl[i].guid, LINUX_EFI_BOOT_MEMMAP_GUID)) {
+						memmap = (unsigned long)tbl[i].table;
+						break;
+					}
+				}
+				early_memunmap(tbl, sizeof(*tbl) * nr_tables);
+			}
+
 			bm = early_memremap_ro(memmap, sizeof(*bm));
 			if (!bm) {
 				pr_err("Cannot remap EFI boot memory map\n");
-- 
2.47.3

Re: [PATCH 1/3] efi: Turn boot memmap handling into shared code

[Richard Lyu]

On 2026/08/13 09:45, Ard Biesheuvel wrote:
>Move the handling of the boot memmap config table from loongarch
>specific code to code that is shared between all architectures that
>select EFI_GENERIC_STUB (all EFI archs except x86).
>
>This will be used in a subsequent patch to replace the clunky FDT based
>passing of the memmap parameters.
>
>Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>---
> arch/loongarch/kernel/efi.c | 10 ++++------
> drivers/firmware/efi/efi.c  |  4 ++++
> include/linux/efi.h         |  3 +++
> 3 files changed, 11 insertions(+), 6 deletions(-)
>
>diff --git a/arch/loongarch/kernel/efi.c b/arch/loongarch/kernel/efi.c
>index 69dd83f8082f..089378856bab 100644
>--- a/arch/loongarch/kernel/efi.c
>+++ b/arch/loongarch/kernel/efi.c
>@@ -28,12 +28,10 @@
> static unsigned long efi_nr_tables;
> static unsigned long efi_config_table;
>
>-static unsigned long __initdata boot_memmap = EFI_INVALID_TABLE_ADDR;
> static unsigned long __initdata fdt_pointer = EFI_INVALID_TABLE_ADDR;
>
> static efi_system_table_t *efi_systab;
> static efi_config_table_type_t arch_tables[] __initdata = {
>-	{LINUX_EFI_BOOT_MEMMAP_GUID,	&boot_memmap,	"MEMMAP" },
> 	{DEVICE_TREE_GUID,		&fdt_pointer,	"FDTPTR" },
> 	{},
> };
>@@ -132,14 +130,14 @@ void __init efi_init(void)
> 	if (IS_ENABLED(CONFIG_EFI_EARLYCON) || IS_ENABLED(CONFIG_SYSFB))
> 		init_primary_display();
>
>-	if (boot_memmap == EFI_INVALID_TABLE_ADDR)
>+	if (efi.boot_memmap == EFI_INVALID_TABLE_ADDR)
> 		return;
>
>-	tbl = early_memremap_ro(boot_memmap, sizeof(*tbl));
>+	tbl = early_memremap_ro(efi.boot_memmap, sizeof(*tbl));
> 	if (tbl) {
> 		struct efi_memory_map_data data;
>
>-		data.phys_map		= boot_memmap + sizeof(*tbl);
>+		data.phys_map		= efi.boot_memmap + sizeof(*tbl);
> 		data.size		= tbl->map_size;
> 		data.desc_size		= tbl->desc_size;
> 		data.desc_version	= tbl->desc_ver;
>@@ -156,7 +154,7 @@ void __init efi_init(void)
> 		 * Also, set the EFI_PRESERVE_BS_REGIONS flag to indicate that
> 		 * critical boot services code/data regions like this are preserved.
> 		 */
>-		memblock_reserve((phys_addr_t)boot_memmap, sizeof(*tbl) + data.size);
>+		memblock_reserve((phys_addr_t)efi.boot_memmap, sizeof(*tbl) + data.size);
> 		set_bit(EFI_PRESERVE_BS_REGIONS, &efi.flags);
>
> 		early_memunmap(tbl, sizeof(*tbl));
>diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
>index 0327a39d31fa..d33760d6a527 100644
>--- a/drivers/firmware/efi/efi.c
>+++ b/drivers/firmware/efi/efi.c
>@@ -55,6 +55,9 @@ struct efi __read_mostly efi = {
> #ifdef CONFIG_UNACCEPTED_MEMORY
> 	.unaccepted		= EFI_INVALID_TABLE_ADDR,
> #endif
>+#ifdef CONFIG_EFI_GENERIC_STUB
>+	.boot_memmap		= EFI_INVALID_TABLE_ADDR,
>+#endif
> };
> EXPORT_SYMBOL(efi);
>
>@@ -647,6 +650,7 @@ static const efi_config_table_type_t common_tables[] __initconst = {
> 	{LINUX_EFI_UNACCEPTED_MEM_TABLE_GUID,	&efi.unaccepted,	"Unaccepted"	},
> #endif
> #ifdef CONFIG_EFI_GENERIC_STUB
>+	{LINUX_EFI_BOOT_MEMMAP_GUID,		&efi.boot_memmap,	"MEMMAP"	},
> 	{LINUX_EFI_PRIMARY_DISPLAY_TABLE_GUID,	&primary_display_table			},
> #endif
> 	{},
>diff --git a/include/linux/efi.h b/include/linux/efi.h
>index aa15ff88539b..bc1cd005ca0f 100644
>--- a/include/linux/efi.h
>+++ b/include/linux/efi.h
>@@ -650,6 +650,9 @@ extern struct efi {
> 	unsigned long			mokvar_table;		/* MOK variable config table */
> 	unsigned long			coco_secret;		/* Confidential computing secret table */
> 	unsigned long			unaccepted;		/* Unaccepted memory table */
>+#ifdef CONFIG_EFI_GENERIC_STUB
>+	unsigned long			boot_memmap;		/* The EFI memory map captured by the stub */
>+#endif
>
> 	efi_get_time_t			*get_time;
> 	efi_set_time_t			*set_time;
>-- 
>2.47.3
>
>

Reviewed-by: Richard Lyu <richard.lyu@suse.com>

Re: [PATCH 2/3] efi: Pass EFI boot memmap struct address to core kernel

[Richard Lyu]

On 2026/08/13 09:45, Ard Biesheuvel wrote:
>The EFI stub already passes a struct efi_boot_memmap populated with the
>information of the EFI memory map as a configuration table, and so
>passing the physical address, size, descriptor size and descriptor
>version via 4 different DT properties is kind of redundant.
>
>Instead, pass the physical address of this struct in memory so that the
>kernel can just retrieve the values directly.
>
>Unfortunately, the scheme with four separate properties is boot ABI for
>Xen, and so this needs to remain supported. But for the EFI stub itself,
>this is just an internal ABI that can be modified.
>
>Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>---
> Documentation/arch/arm/uefi.rst    | 10 +----
> drivers/firmware/efi/fdtparams.c   | 39 ++++++++++++++++---
> drivers/firmware/efi/libstub/fdt.c | 40 ++------------------
> 3 files changed, 37 insertions(+), 52 deletions(-)
>
>diff --git a/Documentation/arch/arm/uefi.rst b/Documentation/arch/arm/uefi.rst
>index 2b7ad9bd7cd2..c19cf3720f27 100644
>--- a/Documentation/arch/arm/uefi.rst
>+++ b/Documentation/arch/arm/uefi.rst
>@@ -54,17 +54,9 @@ Name                        Type     Description
> ==========================  ======   ===========================================
> linux,uefi-system-table     64-bit   Physical address of the UEFI System Table.
>
>-linux,uefi-mmap-start       64-bit   Physical address of the UEFI memory map,
>+linux,uefi-boot-memmap      64-bit   Physical address of a struct efi_boot_memmap
>                                      populated by the UEFI GetMemoryMap() call.
>
>-linux,uefi-mmap-size        32-bit   Size in bytes of the UEFI memory map
>-                                     pointed to in previous entry.
>-
>-linux,uefi-mmap-desc-size   32-bit   Size in bytes of each entry in the UEFI
>-                                     memory map.
>-
>-linux,uefi-mmap-desc-ver    32-bit   Version of the mmap descriptor format.
>-
> kaslr-seed                  64-bit   Entropy used to randomize the kernel image
>                                      base address location.
>
>diff --git a/drivers/firmware/efi/fdtparams.c b/drivers/firmware/efi/fdtparams.c
>index b815d2a754ee..a54a76a6aaeb 100644
>--- a/drivers/firmware/efi/fdtparams.c
>+++ b/drivers/firmware/efi/fdtparams.c
>@@ -10,22 +10,30 @@
>
> #include <linux/unaligned.h>
>
>+#include <asm/early_ioremap.h>
>+
> enum {
> 	SYSTAB,
>+	MEMMAP,
>+#ifdef CONFIG_XEN
> 	MMBASE,
> 	MMSIZE,
> 	DCSIZE,
> 	DCVERS,
>+#endif
>
> 	PARAMCOUNT
> };
>
> static __initconst const char name[][22] = {
> 	[SYSTAB] = "System Table         ",
>+	[MEMMAP] = "Boot Memory Map      ",
>+#ifdef CONFIG_XEN
> 	[MMBASE] = "MemMap Address       ",
> 	[MMSIZE] = "MemMap Size          ",
> 	[DCSIZE] = "MemMap Desc. Size    ",
> 	[DCVERS] = "MemMap Desc. Version ",
>+#endif
> };
>
> static __initconst const struct {
>@@ -49,10 +57,7 @@ static __initconst const struct {
> 		.path = "/chosen",
> 		.params = {	//  <-----------26----------->
> 			[SYSTAB] = "linux,uefi-system-table",
>-			[MMBASE] = "linux,uefi-mmap-start",
>-			[MMSIZE] = "linux,uefi-mmap-size",
>-			[DCSIZE] = "linux,uefi-mmap-desc-size",
>-			[DCVERS] = "linux,uefi-mmap-desc-ver",
>+			[MEMMAP] = "linux,uefi-boot-memmap",
> 		}
> 	}
> };
>@@ -84,17 +89,20 @@ static int __init efi_get_fdt_prop(const void *fdt, int node, const char *pname,
> u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
> {
> 	const void *fdt = initial_boot_params;
>-	unsigned long systab;
>+	unsigned long systab, memmap;
> 	int i, j, node;
> 	struct {
> 		void	*var;
> 		int	size;
> 	} target[] = {
> 		[SYSTAB] = { &systab,		sizeof(systab) },
>+		[MEMMAP] = { &memmap,		sizeof(memmap) },
>+#ifdef CONFIG_XEN
> 		[MMBASE] = { &mm->phys_map,	sizeof(mm->phys_map) },
> 		[MMSIZE] = { &mm->size,		sizeof(mm->size) },
> 		[DCSIZE] = { &mm->desc_size,	sizeof(mm->desc_size) },
> 		[DCVERS] = { &mm->desc_version,	sizeof(mm->desc_version) },
>+#endif
> 	};
>
> 	BUILD_BUG_ON(ARRAY_SIZE(target) != ARRAY_SIZE(name));
>@@ -115,6 +123,9 @@ u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
> 		for (j = 0; j < ARRAY_SIZE(target); j++) {
> 			const char *pname = dt_params[i].params[j];
>
>+			if (pname[0] == '\0')
>+				continue;
>+
> 			if (!efi_get_fdt_prop(fdt, node, pname, name[j],
> 					      target[j].var, target[j].size))
> 				continue;
>@@ -123,8 +134,24 @@ u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
> 			pr_err("Can't find property '%s' in DT!\n", pname);
> 			return 0;
> 		}
>-		if (dt_params[i].paravirt)
>+		if (IS_ENABLED(CONFIG_XEN) && dt_params[i].paravirt) {
> 			set_bit(EFI_PARAVIRT, &efi.flags);
>+		} else {
>+			struct efi_boot_memmap *bm;
>+
>+			bm = early_memremap_ro(memmap, sizeof(*bm));
>+			if (!bm) {
>+				pr_err("Cannot remap EFI boot memory map\n");
>+				return 0;
>+			}
>+
>+			mm->phys_map		= memmap + sizeof(*bm);
>+			mm->size		= bm->map_size;
>+			mm->desc_size		= bm->desc_size;
>+			mm->desc_version	= bm->desc_ver;
>+
>+			early_memunmap(bm, sizeof(*bm));
>+		}
> 		return systab;
> 	}
> notfound:
>diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
>index 23b3543d3041..417b1344bdd8 100644
>--- a/drivers/firmware/efi/libstub/fdt.c
>+++ b/drivers/firmware/efi/libstub/fdt.c
>@@ -32,7 +32,6 @@ static efi_status_t update_fdt(void *orig_fdt, unsigned long orig_fdt_size,
> {
> 	int node, num_rsv;
> 	int status;
>-	fdt32_t fdt_val32;
> 	fdt64_t fdt_val64;
>
> 	/* Do some checks on provided FDT, if it exists: */
>@@ -102,21 +101,7 @@ static efi_status_t update_fdt(void *orig_fdt, unsigned long orig_fdt_size,
>
> 	fdt_val64 = cpu_to_fdt64(U64_MAX); /* placeholder */
>
>-	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-start", fdt_val64);
>-	if (status)
>-		goto fdt_set_fail;
>-
>-	fdt_val32 = cpu_to_fdt32(U32_MAX); /* placeholder */
>-
>-	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-size", fdt_val32);
>-	if (status)
>-		goto fdt_set_fail;
>-
>-	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-desc-size", fdt_val32);
>-	if (status)
>-		goto fdt_set_fail;
>-
>-	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-desc-ver", fdt_val32);
>+	status = fdt_setprop_var(fdt, node, "linux,uefi-boot-memmap", fdt_val64);
> 	if (status)
> 		goto fdt_set_fail;
>
>@@ -148,33 +133,14 @@ static efi_status_t update_fdt_memmap(void *fdt, struct efi_boot_memmap *map)
> {
> 	int node = fdt_path_offset(fdt, "/chosen");
> 	fdt64_t fdt_val64;
>-	fdt32_t fdt_val32;
> 	int err;
>
> 	if (node < 0)
> 		return EFI_LOAD_ERROR;
>
>-	fdt_val64 = cpu_to_fdt64((unsigned long)map->map);
>-
>-	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-start", fdt_val64);
>-	if (err)
>-		return EFI_LOAD_ERROR;
>-
>-	fdt_val32 = cpu_to_fdt32(map->map_size);
>-
>-	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-size", fdt_val32);
>-	if (err)
>-		return EFI_LOAD_ERROR;
>-
>-	fdt_val32 = cpu_to_fdt32(map->desc_size);
>-
>-	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-desc-size", fdt_val32);
>-	if (err)
>-		return EFI_LOAD_ERROR;
>-
>-	fdt_val32 = cpu_to_fdt32(map->desc_ver);
>+	fdt_val64 = cpu_to_fdt64((unsigned long)map);
>
>-	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-desc-ver", fdt_val32);
>+	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-boot-memmap", fdt_val64);
> 	if (err)
> 		return EFI_LOAD_ERROR;
>
>-- 
>2.47.3
>
>

Reviewed-by: Richard Lyu <richard.lyu@suse.com>

Re: [PATCH 3/3] efi: Make the 'linux,uefi-boot-memmap' DT property optional

[Richard Lyu]

On 2026/08/13 09:45, Ard Biesheuvel wrote:
>The 'linux,uefi-boot-memmap DT property' is redundant in principle,
>given that it carries a physical address that is also passed via a EFI
>config table entry.
>
>However, if SetVirtualAddressMap() has been called, the address of the
>config table array has been translated to virtual, and so the memory map
>is needed to translate it back to physical before it can be located.
>
>This means that passing the linux,uefi-boot-memmap DT property is only
>needed if SetVirtualAddressMap() has been called, which is a terrible
>idea anyway, and if it has not been called, the config table array can
>simply be parsed to look for LINUX_EFI_BOOT_MEMMAP_TABLE_GUID, and the
>address taken from there.
>
>So permit this, and make the boot memmap property optional.
>
>Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>---
> drivers/firmware/efi/fdtparams.c | 42 ++++++++++++++++++--
> 1 file changed, 38 insertions(+), 4 deletions(-)
>
>diff --git a/drivers/firmware/efi/fdtparams.c b/drivers/firmware/efi/fdtparams.c
>index a54a76a6aaeb..89ffccf35fd7 100644
>--- a/drivers/firmware/efi/fdtparams.c
>+++ b/drivers/firmware/efi/fdtparams.c
>@@ -89,14 +89,15 @@ static int __init efi_get_fdt_prop(const void *fdt, int node, const char *pname,
> u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
> {
> 	const void *fdt = initial_boot_params;
>-	unsigned long systab, memmap;
>+	unsigned long systab, memmap = 0;
> 	int i, j, node;
> 	struct {
> 		void	*var;
> 		int	size;
>+		int	optional;
> 	} target[] = {
> 		[SYSTAB] = { &systab,		sizeof(systab) },
>-		[MEMMAP] = { &memmap,		sizeof(memmap) },
>+		[MEMMAP] = { &memmap,		sizeof(memmap), 1 },
> #ifdef CONFIG_XEN
> 		[MMBASE] = { &mm->phys_map,	sizeof(mm->phys_map) },
> 		[MMSIZE] = { &mm->size,		sizeof(mm->size) },
>@@ -131,14 +132,47 @@ u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
> 				continue;
> 			if (!j)
> 				goto notfound;
>-			pr_err("Can't find property '%s' in DT!\n", pname);
>-			return 0;
>+			if (!target[j].optional) {
>+				pr_err("Can't find property '%s' in DT!\n", pname);
>+				return 0;
>+			}
> 		}
> 		if (IS_ENABLED(CONFIG_XEN) && dt_params[i].paravirt) {
> 			set_bit(EFI_PARAVIRT, &efi.flags);
> 		} else {
> 			struct efi_boot_memmap *bm;
>
>+			if (!memmap) {
>+				unsigned long tables, nr_tables;
>+				efi_system_table_t *st;
>+				efi_config_table_t *tbl;
>+
>+				st = early_memremap_ro(systab, sizeof(*st));
>+				if (!st) {
>+					pr_err("Cannot remap EFI system table\n");
>+					return 0;
>+				}
>+
>+				tables		= st->tables;
>+				nr_tables	= st->nr_tables;
>+
>+				early_memunmap(st, sizeof(*st));
>+
>+				tbl = early_memremap_ro(tables, sizeof(*tbl) * nr_tables);
>+				if (!tbl) {
>+					pr_err("Cannot remap EFI config table array\n");
>+					return 0;
>+				}
>+
>+				for (int i = 0; i < nr_tables; i++) {
>+					if (!efi_guidcmp(tbl[i].guid, LINUX_EFI_BOOT_MEMMAP_GUID)) {
>+						memmap = (unsigned long)tbl[i].table;
>+						break;
>+					}
>+				}
>+				early_memunmap(tbl, sizeof(*tbl) * nr_tables);
>+			}
>+
> 			bm = early_memremap_ro(memmap, sizeof(*bm));
> 			if (!bm) {
> 				pr_err("Cannot remap EFI boot memory map\n");
>-- 
>2.47.3
>
>

Reviewed-by: Richard Lyu <richard.lyu@suse.com>