[PATCH v3 0/3] LoongArch: add KHO support and selftests

[PATCH v3 0/3] LoongArch: add KHO support and selftests

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

This series adds Kexec Handover (KHO) support for LoongArch and extends
the KHO selftest infrastructure to run on LoongArch under QEMU.

KHO passes metadata (the KHO state FDT and scratch area addresses) to the
second kernel via the FDT /chosen node, using the linux,kho-fdt and
linux,kho-scratch properties that drivers/of/kexec.c:kho_add_chosen()
writes and drivers/of/fdt.c:early_init_dt_check_kho() reads.

KHO support (patches 1-2):

Patch 1 adds KHO support for FDT-based systems (initial_boot_params !=
NULL, e.g. QEMU virt without OVMF).  kho_load_fdt() copies the running
kernel's FDT, appends linux,kho-fdt and linux,kho-scratch to /chosen,
and loads the result as a kexec segment.  machine_kexec() updates the
DEVICE_TREE_GUID entry in the EFI config table to point to this segment
so the second kernel's fdt_setup() can find and parse it.

Patch 2 adds KHO support for ACPI-only systems (initial_boot_params ==
NULL, e.g. LoongArch servers with UEFI or QEMU with OVMF).  Because no
system FDT is available, kho_load_fdt() builds a minimal FDT from
scratch containing only /chosen with the two KHO properties.  Since
DEVICE_TREE_GUID is absent from the EFI config table on ACPI-only
systems, a new extended config table is built with the entry appended
and loaded as a kexec segment; machine_kexec() switches st->tables to
point to it before jumping.  The second kernel's fdt_setup() calls
efi_fdt_pointer() to detect the KHO FDT and passes it to
early_init_dt_check_kho().

Selftest support (patch 3):

Patch 3 adds loongarch.conf and extends vmtest.sh to recognise loongarch64
as a build target.  The LoongArch virt machine is FDT-only (no ACPI), so
'earlycon' must appear on the kernel cmdline or the console UART is never
discovered.  PS/2 input devices are disabled since QEMU's LoongArch virt
machine has no i8042 controller; the fallback port probe hits a page fault
and panics before reaching userspace.  QEMU provides no EFI runtime
services on LoongArch, so machine_restart() falls through to an infinite
idle loop after kexec; QEMU_TIMEOUT=120 in loongarch.conf lets timeout(1)
terminate QEMU once the time limit is reached.

Changes in v3:
- Merge selftest patches 3 and 4 from v2 into a single patch
- Replace QEMU_NEEDS_KILL/background kill loop with QEMU_TIMEOUT/timeout(1);
  the timeout value is set per-arch in the conf file.

George Guo (3):
  LoongArch: kexec: add KHO support for FDT-based systems
  LoongArch: kexec: add KHO support for ACPI-only systems
  selftests/kho: add LoongArch vmtest support

 arch/loongarch/Kconfig                     |   3 +
 arch/loongarch/include/asm/kexec.h         |   7 +
 arch/loongarch/kernel/machine_kexec.c      |  38 +++
 arch/loongarch/kernel/machine_kexec_file.c | 256 +++++++++++++++++++++
 arch/loongarch/kernel/setup.c              |  21 +-
 tools/testing/selftests/kho/loongarch.conf |  13 ++
 tools/testing/selftests/kho/vmtest.sh      |  23 +-
 7 files changed, 353 insertions(+), 8 deletions(-)
 create mode 100644 tools/testing/selftests/kho/loongarch.conf

--
2.25.1

[PATCH v3 1/3] LoongArch: kexec: add KHO support for FDT-based

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

Enable Kexec Handover (KHO) on LoongArch64 for FDT-based systems.

- Kconfig: select ARCH_SUPPORTS_KEXEC_HANDOVER for CONFIG_64BIT
- kexec.h: add fdt/fdt_mem fields to kimage_arch to hold the KHO FDT
  kexec segment virtual and physical addresses
- machine_kexec_file.c: add kho_load_fdt() which copies the running
  kernel's FDT (initial_boot_params), appends linux,kho-fdt and
  linux,kho-scratch properties to /chosen, and loads the result as a
  kexec segment; called from load_other_segments().  Returns -EINVAL
  when initial_boot_params is NULL (ACPI-only boot) since that path
  requires separate handling.
- machine_kexec.c: before jumping to the new kernel, update the
  DEVICE_TREE_GUID entry in the EFI config table to point to the KHO
  FDT segment so the second kernel finds it via efi_fdt_pointer() and
  early_init_dt_check_kho() calls kho_populate()

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 arch/loongarch/Kconfig                     |   3 +
 arch/loongarch/include/asm/kexec.h         |   4 +
 arch/loongarch/kernel/machine_kexec.c      |  27 +++++
 arch/loongarch/kernel/machine_kexec_file.c | 118 +++++++++++++++++++++
 4 files changed, 152 insertions(+)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 606597da46b8..d494418545f5 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -684,6 +684,9 @@ config ARCH_SUPPORTS_KEXEC
 config ARCH_SUPPORTS_KEXEC_FILE
 	def_bool 64BIT
 
+config ARCH_SUPPORTS_KEXEC_HANDOVER
+	def_bool 64BIT
+
 config ARCH_SELECTS_KEXEC_FILE
 	def_bool 64BIT
 	depends on KEXEC_FILE
diff --git a/arch/loongarch/include/asm/kexec.h b/arch/loongarch/include/asm/kexec.h
index 209fa43222e1..adf54bfcdd49 100644
--- a/arch/loongarch/include/asm/kexec.h
+++ b/arch/loongarch/include/asm/kexec.h
@@ -39,6 +39,10 @@ struct kimage_arch {
 	unsigned long efi_boot;
 	unsigned long cmdline_ptr;
 	unsigned long systable_ptr;
+#ifdef CONFIG_KEXEC_HANDOVER
+	void *fdt;		/* virtual address of KHO FDT segment buffer */
+	unsigned long fdt_mem;	/* physical address of KHO FDT segment */
+#endif
 };
 
 #ifdef CONFIG_KEXEC_FILE
diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
index ad27fef098f1..98529c71d001 100644
--- a/arch/loongarch/kernel/machine_kexec.c
+++ b/arch/loongarch/kernel/machine_kexec.c
@@ -6,6 +6,7 @@
  */
 #include <linux/compiler.h>
 #include <linux/cpu.h>
+#include <linux/efi.h>
 #include <linux/kexec.h>
 #include <linux/crash_dump.h>
 #include <linux/delay.h>
@@ -289,6 +290,32 @@ void machine_kexec(struct kimage *image)
 	pr_notice("We will call new kernel at 0x%lx\n", start_addr);
 	pr_notice("Bye ...\n");
 
+#ifdef CONFIG_KEXEC_HANDOVER
+	/*
+	 * Point the EFI FDTPTR config table entry at the modified FDT so the
+	 * second kernel picks up the linux,kho-fdt and linux,kho-scratch
+	 * properties via early_init_dt_check_kho().
+	 */
+	if (internal->fdt_mem) {
+		/*
+		 * FDT-based system: DEVICE_TREE_GUID already exists in the EFI
+		 * config table; just update its pointer to our KHO FDT.
+		 */
+		efi_system_table_t *st =
+			(efi_system_table_t *)TO_CACHE(systable_ptr);
+		efi_config_table_t *ct =
+			(efi_config_table_t *)TO_CACHE((unsigned long)st->tables);
+		unsigned long i;
+
+		for (i = 0; i < st->nr_tables; i++) {
+			if (!efi_guidcmp(ct[i].guid, DEVICE_TREE_GUID)) {
+				ct[i].table = (void *)internal->fdt_mem;
+				break;
+			}
+		}
+	}
+#endif
+
 	/* Make reboot code buffer available to the boot CPU. */
 	flush_cache_all();
 
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index 5584b798ba46..bf1e8c1c7e70 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -13,7 +13,9 @@
 #include <linux/ioport.h>
 #include <linux/kernel.h>
 #include <linux/kexec.h>
+#include <linux/libfdt.h>
 #include <linux/memblock.h>
+#include <linux/of_fdt.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/types.h>
@@ -32,6 +34,11 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 	image->elf_headers = NULL;
 	image->elf_headers_sz = 0;
 
+#ifdef CONFIG_KEXEC_HANDOVER
+	kvfree(image->arch.fdt);
+	image->arch.fdt = NULL;
+#endif
+
 	return kexec_image_post_load_cleanup_default(image);
 }
 
@@ -55,6 +62,111 @@ static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmpl
 	*cmdline_tmplen += initrd_strlen;
 }
 
+#ifdef CONFIG_KEXEC_HANDOVER
+/*
+ * Add KHO metadata to an FDT /chosen node and load the FDT as a kexec
+ * segment.  The second kernel reads linux,kho-fdt and linux,kho-scratch
+ * from /chosen via early_init_dt_check_kho() and calls kho_populate().
+ *
+ */
+static int kho_load_fdt(struct kimage *image)
+{
+	void *fdt;
+	int ret, chosen_node;
+	size_t fdt_size;
+	struct kexec_buf kbuf = {
+		.image		= image,
+		.buf_min	= 0,
+		.buf_max	= ULONG_MAX,
+		.top_down	= true,
+	};
+
+	if (!image->kho.fdt || !image->kho.scratch)
+		return 0;
+
+	if (initial_boot_params) {
+		/*
+		 * FDT boot: copy the running kernel's FDT and append KHO
+		 * properties to /chosen.
+		 */
+
+		/*
+		 * Only two KHO properties are added to /chosen (linux,kho-fdt
+		 * and linux,kho-scratch), so SZ_1K of extra space is
+		 * sufficient.
+		 */
+		fdt_size = fdt_totalsize(initial_boot_params) + SZ_1K;
+		fdt = kvmalloc(fdt_size, GFP_KERNEL);
+		if (!fdt)
+			return -ENOMEM;
+
+		ret = fdt_open_into(initial_boot_params, fdt, fdt_size);
+		if (ret < 0) {
+			pr_err("Failed to open FDT: %d\n", ret);
+			goto out_free;
+		}
+
+		chosen_node = fdt_path_offset(fdt, "/chosen");
+		if (chosen_node == -FDT_ERR_NOTFOUND) {
+			pr_debug("No /chosen node in FDT, creating one\n");
+			chosen_node = fdt_add_subnode(fdt,
+						      fdt_path_offset(fdt, "/"),
+						      "chosen");
+		}
+		if (chosen_node < 0) {
+			ret = chosen_node;
+			goto out_free;
+		}
+
+		/* Remove stale KHO properties left by a previous kexec load */
+		fdt_delprop(fdt, chosen_node, "linux,kho-fdt");
+		fdt_delprop(fdt, chosen_node, "linux,kho-scratch");
+
+		ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
+					       "linux,kho-fdt",
+					       image->kho.fdt, PAGE_SIZE);
+		if (ret)
+			goto out_free;
+
+		ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
+					       "linux,kho-scratch",
+					       image->kho.scratch->mem,
+					       image->kho.scratch->bufsz);
+		if (ret)
+			goto out_free;
+
+		/*
+		 * Shrink totalsize to the actual data size so the kexec segment
+		 * allocated by kexec_add_buffer() covers only the packed FDT data.
+		 * The slack added above for property insertion is part of the
+		 * kvmalloc'd buffer, which is freed by kimage_file_post_load_cleanup()
+		 * once the kexec image has been loaded.
+		 */
+		fdt_pack(fdt);
+
+		kbuf.buffer	= fdt;
+		kbuf.bufsz	= fdt_totalsize(fdt);
+		kbuf.memsz	= kbuf.bufsz;
+		kbuf.buf_align	= PAGE_SIZE;
+		kbuf.mem	= KEXEC_BUF_MEM_UNKNOWN;
+
+		ret = kexec_add_buffer(&kbuf);
+		if (ret)
+			goto out_free;
+
+		image->arch.fdt     = fdt;
+		image->arch.fdt_mem = kbuf.mem;
+		return 0;
+	} else {
+		return -EINVAL;
+	}
+
+out_free:
+	kvfree(fdt);
+	return ret;
+}
+#endif
+
 #ifdef CONFIG_CRASH_DUMP
 
 static int prepare_elf_headers(void **addr, unsigned long *sz)
@@ -230,6 +342,12 @@ int load_other_segments(struct kimage *image,
 	cmdline = modified_cmdline;
 	image->arch.cmdline_ptr = (unsigned long)cmdline;
 
+#ifdef CONFIG_KEXEC_HANDOVER
+	ret = kho_load_fdt(image);
+	if (ret)
+		goto out_err;
+#endif
+
 	return 0;
 
 out_err:
-- 
2.25.1

[PATCH v3 1/3] LoongArch: kexec: add KHO support for FDT-based

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

Enable Kexec Handover (KHO) on LoongArch64 for FDT-based systems.

- Kconfig: select ARCH_SUPPORTS_KEXEC_HANDOVER for CONFIG_64BIT
- kexec.h: add fdt/fdt_mem fields to kimage_arch to hold the KHO FDT
  kexec segment virtual and physical addresses
- machine_kexec_file.c: add kho_load_fdt() which copies the running
  kernel's FDT (initial_boot_params), appends linux,kho-fdt and
  linux,kho-scratch properties to /chosen, and loads the result as a
  kexec segment; called from load_other_segments().  Returns -EINVAL
  when initial_boot_params is NULL (ACPI-only boot) since that path
  requires separate handling.
- machine_kexec.c: before jumping to the new kernel, update the
  DEVICE_TREE_GUID entry in the EFI config table to point to the KHO
  FDT segment so the second kernel finds it via efi_fdt_pointer() and
  early_init_dt_check_kho() calls kho_populate()

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 arch/loongarch/Kconfig                     |   3 +
 arch/loongarch/include/asm/kexec.h         |   4 +
 arch/loongarch/kernel/machine_kexec.c      |  27 +++++
 arch/loongarch/kernel/machine_kexec_file.c | 118 +++++++++++++++++++++
 4 files changed, 152 insertions(+)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 606597da46b8..d494418545f5 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -684,6 +684,9 @@ config ARCH_SUPPORTS_KEXEC
 config ARCH_SUPPORTS_KEXEC_FILE
 	def_bool 64BIT
 
+config ARCH_SUPPORTS_KEXEC_HANDOVER
+	def_bool 64BIT
+
 config ARCH_SELECTS_KEXEC_FILE
 	def_bool 64BIT
 	depends on KEXEC_FILE
diff --git a/arch/loongarch/include/asm/kexec.h b/arch/loongarch/include/asm/kexec.h
index 209fa43222e1..adf54bfcdd49 100644
--- a/arch/loongarch/include/asm/kexec.h
+++ b/arch/loongarch/include/asm/kexec.h
@@ -39,6 +39,10 @@ struct kimage_arch {
 	unsigned long efi_boot;
 	unsigned long cmdline_ptr;
 	unsigned long systable_ptr;
+#ifdef CONFIG_KEXEC_HANDOVER
+	void *fdt;		/* virtual address of KHO FDT segment buffer */
+	unsigned long fdt_mem;	/* physical address of KHO FDT segment */
+#endif
 };
 
 #ifdef CONFIG_KEXEC_FILE
diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
index ad27fef098f1..98529c71d001 100644
--- a/arch/loongarch/kernel/machine_kexec.c
+++ b/arch/loongarch/kernel/machine_kexec.c
@@ -6,6 +6,7 @@
  */
 #include <linux/compiler.h>
 #include <linux/cpu.h>
+#include <linux/efi.h>
 #include <linux/kexec.h>
 #include <linux/crash_dump.h>
 #include <linux/delay.h>
@@ -289,6 +290,32 @@ void machine_kexec(struct kimage *image)
 	pr_notice("We will call new kernel at 0x%lx\n", start_addr);
 	pr_notice("Bye ...\n");
 
+#ifdef CONFIG_KEXEC_HANDOVER
+	/*
+	 * Point the EFI FDTPTR config table entry at the modified FDT so the
+	 * second kernel picks up the linux,kho-fdt and linux,kho-scratch
+	 * properties via early_init_dt_check_kho().
+	 */
+	if (internal->fdt_mem) {
+		/*
+		 * FDT-based system: DEVICE_TREE_GUID already exists in the EFI
+		 * config table; just update its pointer to our KHO FDT.
+		 */
+		efi_system_table_t *st =
+			(efi_system_table_t *)TO_CACHE(systable_ptr);
+		efi_config_table_t *ct =
+			(efi_config_table_t *)TO_CACHE((unsigned long)st->tables);
+		unsigned long i;
+
+		for (i = 0; i < st->nr_tables; i++) {
+			if (!efi_guidcmp(ct[i].guid, DEVICE_TREE_GUID)) {
+				ct[i].table = (void *)internal->fdt_mem;
+				break;
+			}
+		}
+	}
+#endif
+
 	/* Make reboot code buffer available to the boot CPU. */
 	flush_cache_all();
 
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index 5584b798ba46..bf1e8c1c7e70 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -13,7 +13,9 @@
 #include <linux/ioport.h>
 #include <linux/kernel.h>
 #include <linux/kexec.h>
+#include <linux/libfdt.h>
 #include <linux/memblock.h>
+#include <linux/of_fdt.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/types.h>
@@ -32,6 +34,11 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 	image->elf_headers = NULL;
 	image->elf_headers_sz = 0;
 
+#ifdef CONFIG_KEXEC_HANDOVER
+	kvfree(image->arch.fdt);
+	image->arch.fdt = NULL;
+#endif
+
 	return kexec_image_post_load_cleanup_default(image);
 }
 
@@ -55,6 +62,111 @@ static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmpl
 	*cmdline_tmplen += initrd_strlen;
 }
 
+#ifdef CONFIG_KEXEC_HANDOVER
+/*
+ * Add KHO metadata to an FDT /chosen node and load the FDT as a kexec
+ * segment.  The second kernel reads linux,kho-fdt and linux,kho-scratch
+ * from /chosen via early_init_dt_check_kho() and calls kho_populate().
+ *
+ */
+static int kho_load_fdt(struct kimage *image)
+{
+	void *fdt;
+	int ret, chosen_node;
+	size_t fdt_size;
+	struct kexec_buf kbuf = {
+		.image		= image,
+		.buf_min	= 0,
+		.buf_max	= ULONG_MAX,
+		.top_down	= true,
+	};
+
+	if (!image->kho.fdt || !image->kho.scratch)
+		return 0;
+
+	if (initial_boot_params) {
+		/*
+		 * FDT boot: copy the running kernel's FDT and append KHO
+		 * properties to /chosen.
+		 */
+
+		/*
+		 * Only two KHO properties are added to /chosen (linux,kho-fdt
+		 * and linux,kho-scratch), so SZ_1K of extra space is
+		 * sufficient.
+		 */
+		fdt_size = fdt_totalsize(initial_boot_params) + SZ_1K;
+		fdt = kvmalloc(fdt_size, GFP_KERNEL);
+		if (!fdt)
+			return -ENOMEM;
+
+		ret = fdt_open_into(initial_boot_params, fdt, fdt_size);
+		if (ret < 0) {
+			pr_err("Failed to open FDT: %d\n", ret);
+			goto out_free;
+		}
+
+		chosen_node = fdt_path_offset(fdt, "/chosen");
+		if (chosen_node == -FDT_ERR_NOTFOUND) {
+			pr_debug("No /chosen node in FDT, creating one\n");
+			chosen_node = fdt_add_subnode(fdt,
+						      fdt_path_offset(fdt, "/"),
+						      "chosen");
+		}
+		if (chosen_node < 0) {
+			ret = chosen_node;
+			goto out_free;
+		}
+
+		/* Remove stale KHO properties left by a previous kexec load */
+		fdt_delprop(fdt, chosen_node, "linux,kho-fdt");
+		fdt_delprop(fdt, chosen_node, "linux,kho-scratch");
+
+		ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
+					       "linux,kho-fdt",
+					       image->kho.fdt, PAGE_SIZE);
+		if (ret)
+			goto out_free;
+
+		ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
+					       "linux,kho-scratch",
+					       image->kho.scratch->mem,
+					       image->kho.scratch->bufsz);
+		if (ret)
+			goto out_free;
+
+		/*
+		 * Shrink totalsize to the actual data size so the kexec segment
+		 * allocated by kexec_add_buffer() covers only the packed FDT data.
+		 * The slack added above for property insertion is part of the
+		 * kvmalloc'd buffer, which is freed by kimage_file_post_load_cleanup()
+		 * once the kexec image has been loaded.
+		 */
+		fdt_pack(fdt);
+
+		kbuf.buffer	= fdt;
+		kbuf.bufsz	= fdt_totalsize(fdt);
+		kbuf.memsz	= kbuf.bufsz;
+		kbuf.buf_align	= PAGE_SIZE;
+		kbuf.mem	= KEXEC_BUF_MEM_UNKNOWN;
+
+		ret = kexec_add_buffer(&kbuf);
+		if (ret)
+			goto out_free;
+
+		image->arch.fdt     = fdt;
+		image->arch.fdt_mem = kbuf.mem;
+		return 0;
+	} else {
+		return -EINVAL;
+	}
+
+out_free:
+	kvfree(fdt);
+	return ret;
+}
+#endif
+
 #ifdef CONFIG_CRASH_DUMP
 
 static int prepare_elf_headers(void **addr, unsigned long *sz)
@@ -230,6 +342,12 @@ int load_other_segments(struct kimage *image,
 	cmdline = modified_cmdline;
 	image->arch.cmdline_ptr = (unsigned long)cmdline;
 
+#ifdef CONFIG_KEXEC_HANDOVER
+	ret = kho_load_fdt(image);
+	if (ret)
+		goto out_err;
+#endif
+
 	return 0;
 
 out_err:
-- 
2.25.1

[PATCH v3 2/3] LoongArch: kexec: add KHO support for ACPI-only

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

On ACPI-only systems fdt_setup() returns early when it detects ACPI,
so initial_boot_params remains NULL and the FDT-based kho_load_fdt()
path cannot be used.

machine_kexec_file.c:
- kho_load_fdt(): add an else branch that builds a minimal FDT from
  scratch (SZ_1K) containing only a /chosen node with linux,kho-fdt
  and linux,kho-scratch properties, using the libfdt creation API.
- Since DEVICE_TREE_GUID is absent from the EFI config table on
  ACPI-only systems, build a new config table with DEVICE_TREE_GUID
  appended and load it as a kexec segment.  Store the result in
  kimage_arch so machine_kexec() can switch st->tables before jumping.
- arch_kimage_file_post_load_cleanup(): free the efi_tables kvmalloc
  buffer once the kexec image has been loaded.

machine_kexec.c:
- Before jumping, update the EFI system table pointer: for FDT-based
  systems update the existing DEVICE_TREE_GUID entry; for ACPI-only
  systems switch st->tables / st->nr_tables to the new extended table.

setup.c:
- fdt_setup(): when ACPI is detected, use efi_fdt_pointer() to detect
  whether this is a KHO kexec boot.  The first kernel switches the EFI
  config table to a new one that includes a DEVICE_TREE_GUID entry
  pointing to the minimal KHO FDT.  If found, call early_init_dt_scan()
  so early_init_dt_check_kho() can consume linux,kho-fdt and
  linux,kho-scratch, then reset initial_boot_params to NULL so the rest
  of the ACPI boot path is unaffected.

kexec.h:
- Add efi_tables, efi_tables_mem, efi_tables_cnt to kimage_arch.

Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 arch/loongarch/include/asm/kexec.h         |   3 +
 arch/loongarch/kernel/machine_kexec.c      |  11 ++
 arch/loongarch/kernel/machine_kexec_file.c | 162 +++++++++++++++++++--
 arch/loongarch/kernel/setup.c              |  21 ++-
 4 files changed, 184 insertions(+), 13 deletions(-)

diff --git a/arch/loongarch/include/asm/kexec.h b/arch/loongarch/include/asm/kexec.h
index adf54bfcdd49..e1abaf40b06a 100644
--- a/arch/loongarch/include/asm/kexec.h
+++ b/arch/loongarch/include/asm/kexec.h
@@ -42,6 +42,9 @@ struct kimage_arch {
 #ifdef CONFIG_KEXEC_HANDOVER
 	void *fdt;		/* virtual address of KHO FDT segment buffer */
 	unsigned long fdt_mem;	/* physical address of KHO FDT segment */
+	void *efi_tables;		/* new EFI config table buffer (virtual) */
+	unsigned long efi_tables_mem;	/* physical address of new EFI config table */
+	unsigned long efi_tables_cnt;	/* number of entries in new EFI config table */
 #endif
 };
 
diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
index 98529c71d001..cbb7f8368843 100644
--- a/arch/loongarch/kernel/machine_kexec.c
+++ b/arch/loongarch/kernel/machine_kexec.c
@@ -313,6 +313,17 @@ void machine_kexec(struct kimage *image)
 				break;
 			}
 		}
+	} else if (internal->efi_tables_mem) {
+		/*
+		 * ACPI-only system: DEVICE_TREE_GUID was not in the original
+		 * EFI config table.  Switch to the new table that was built in
+		 * kho_load_fdt() with DEVICE_TREE_GUID appended.
+		 */
+		efi_system_table_t *st =
+			(efi_system_table_t *)TO_CACHE(systable_ptr);
+
+		st->tables    = internal->efi_tables_mem;
+		st->nr_tables = internal->efi_tables_cnt;
 	}
 #endif
 
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index bf1e8c1c7e70..c1955d991061 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -10,6 +10,7 @@
 
 #define pr_fmt(fmt) "kexec_file: " fmt
 
+#include <linux/efi.h>
 #include <linux/ioport.h>
 #include <linux/kernel.h>
 #include <linux/kexec.h>
@@ -20,6 +21,7 @@
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/vmalloc.h>
+#include <asm/addrspace.h>
 #include <asm/bootinfo.h>
 
 const struct kexec_file_ops * const kexec_file_loaders[] = {
@@ -37,6 +39,8 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 #ifdef CONFIG_KEXEC_HANDOVER
 	kvfree(image->arch.fdt);
 	image->arch.fdt = NULL;
+	kvfree(image->arch.efi_tables);
+	image->arch.efi_tables = NULL;
 #endif
 
 	return kexec_image_post_load_cleanup_default(image);
@@ -68,6 +72,13 @@ static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmpl
  * segment.  The second kernel reads linux,kho-fdt and linux,kho-scratch
  * from /chosen via early_init_dt_check_kho() and calls kho_populate().
  *
+ * On FDT-based systems (initial_boot_params != NULL), the current FDT is
+ * copied and the KHO properties are appended to /chosen.
+ *
+ * On ACPI-only systems (initial_boot_params == NULL), a minimal FDT
+ * containing only /chosen is built from scratch.  machine_kexec() updates
+ * the EFI config table DEVICE_TREE_GUID entry to point to this segment so
+ * that the second kernel's fdt_setup() can find and parse it.
  */
 static int kho_load_fdt(struct kimage *image)
 {
@@ -143,24 +154,151 @@ static int kho_load_fdt(struct kimage *image)
 		 * once the kexec image has been loaded.
 		 */
 		fdt_pack(fdt);
+	} else {
+		/*
+		 * ACPI boot: build a minimal FDT containing only /chosen with
+		 * the two KHO properties.  No system FDT is available to copy.
+		 */
 
-		kbuf.buffer	= fdt;
-		kbuf.bufsz	= fdt_totalsize(fdt);
-		kbuf.memsz	= kbuf.bufsz;
-		kbuf.buf_align	= PAGE_SIZE;
-		kbuf.mem	= KEXEC_BUF_MEM_UNKNOWN;
+		__be64 prop[2];
 
-		ret = kexec_add_buffer(&kbuf);
-		if (ret)
+		fdt_size = SZ_1K;
+		fdt = kvmalloc(fdt_size, GFP_KERNEL);
+		if (!fdt)
+			return -ENOMEM;
+
+		ret = fdt_create(fdt, fdt_size);
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_finish_reservemap(fdt);
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_begin_node(fdt, "");	/* root */
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_property_u32(fdt, "#address-cells", 2);
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_property_u32(fdt, "#size-cells", 2);
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_begin_node(fdt, "chosen");
+		if (ret < 0)
 			goto out_free;
 
-		image->arch.fdt     = fdt;
-		image->arch.fdt_mem = kbuf.mem;
-		return 0;
-	} else {
-		return -EINVAL;
+		prop[0] = cpu_to_be64(image->kho.fdt);
+		prop[1] = cpu_to_be64(PAGE_SIZE);
+		ret = fdt_property(fdt, "linux,kho-fdt", prop, sizeof(prop));
+		if (ret < 0)
+			goto out_free;
+
+		prop[0] = cpu_to_be64(image->kho.scratch->mem);
+		prop[1] = cpu_to_be64(image->kho.scratch->bufsz);
+		ret = fdt_property(fdt, "linux,kho-scratch", prop, sizeof(prop));
+		if (ret < 0)
+			goto out_free;
+
+		ret = fdt_end_node(fdt);	/* chosen */
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_end_node(fdt);	/* root */
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_finish(fdt);
+		if (ret < 0)
+			goto out_free;
 	}
 
+	kbuf.buffer	= fdt;
+	kbuf.bufsz	= fdt_totalsize(fdt);
+	kbuf.memsz	= kbuf.bufsz;
+	kbuf.buf_align	= PAGE_SIZE;
+	kbuf.mem	= KEXEC_BUF_MEM_UNKNOWN;
+
+	ret = kexec_add_buffer(&kbuf);
+	if (ret)
+		goto out_free;
+
+	image->arch.fdt     = fdt;
+	image->arch.fdt_mem = kbuf.mem;
+
+	/*
+	 * On ACPI-only systems DEVICE_TREE_GUID is not in the EFI config
+	 * table, so the second kernel's efi_fdt_pointer() cannot locate the
+	 * KHO FDT.  Build a new EFI config table with DEVICE_TREE_GUID added
+	 * and load it as a kexec segment; machine_kexec() will update
+	 * st->tables / st->nr_tables to point to it before jumping.
+	 */
+
+	/*
+	 * fw_arg2 is the EFI system table physical address passed by the
+	 * firmware/bootloader.  Use it directly here because
+	 * image->arch.systable_ptr is set later in machine_kexec_prepare(),
+	 * which runs after load_other_segments() / kho_load_fdt().
+	 */
+	if (!initial_boot_params && fw_arg2) {
+		efi_system_table_t *st =
+			(efi_system_table_t *)TO_CACHE(fw_arg2);
+		efi_config_table_t *ct =
+			(efi_config_table_t *)TO_CACHE((unsigned long)st->tables);
+		unsigned long i;
+		bool found = false;
+
+		/*
+		 * Scan the original config table;
+		 * DEVICE_TREE_GUID is absent on ACPI-only systems.
+		 */
+		for (i = 0; i < st->nr_tables; i++) {
+			if (!efi_guidcmp(ct[i].guid, DEVICE_TREE_GUID)) {
+				found = true;
+				break;
+			}
+		}
+
+		if (!found) {
+			size_t old_sz = st->nr_tables * sizeof(efi_config_table_t);
+			size_t new_sz = old_sz + sizeof(efi_config_table_t);
+			efi_config_table_t *new_ct;
+			struct kexec_buf tbuf = {
+				.image		= image,
+				.buf_min	= 0,
+				.buf_max	= ULONG_MAX,
+				.top_down	= true,
+			};
+
+			/*
+			 * Allocate a new table with n+1 entries and append
+			 * the DEVICE_TREE_GUID entry.
+			 */
+			new_ct = kvmalloc(new_sz, GFP_KERNEL);
+			if (!new_ct)
+				return -ENOMEM;
+
+			memcpy(new_ct, ct, old_sz);
+			new_ct[st->nr_tables].guid  = DEVICE_TREE_GUID;
+			new_ct[st->nr_tables].table = (void *)image->arch.fdt_mem;
+
+			/* Register the new config table as a kexec segment. */
+			tbuf.buffer   = new_ct;
+			tbuf.bufsz    = new_sz;
+			tbuf.memsz    = new_sz;
+			tbuf.buf_align = sizeof(void *);
+			tbuf.mem      = KEXEC_BUF_MEM_UNKNOWN;
+
+			ret = kexec_add_buffer(&tbuf);
+			if (ret) {
+				kvfree(new_ct);
+				return ret;
+			}
+
+			image->arch.efi_tables     = new_ct;
+			image->arch.efi_tables_mem = tbuf.mem;
+			image->arch.efi_tables_cnt = st->nr_tables + 1;
+		}
+	}
+
+	return 0;
+
 out_free:
 	kvfree(fdt);
 	return ret;
diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 839b23edee87..c82067d1dc75 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -286,8 +286,27 @@ static void __init fdt_setup(void)
 	void *fdt_pointer;
 
 	/* ACPI-based systems do not require parsing fdt */
-	if (acpi_os_get_root_pointer())
+	if (acpi_os_get_root_pointer()) {
+#ifdef CONFIG_KEXEC_HANDOVER
+		/*
+		 * On a KHO kexec boot the first kernel builds a minimal FDT
+		 * containing only /chosen with linux,kho-fdt and
+		 * linux,kho-scratch, and switches the EFI config table to a
+		 * new one that includes a DEVICE_TREE_GUID entry pointing to
+		 * it.  Use efi_fdt_pointer() to detect this case.
+		 *
+		 * Call early_init_dt_scan() to let early_init_dt_check_kho()
+		 * consume the KHO data, then reset initial_boot_params so the
+		 * rest of the ACPI boot path is not confused by this FDT.
+		 */
+		fdt_pointer = efi_fdt_pointer();
+		if (fdt_pointer && !fdt_check_header(fdt_pointer)) {
+			early_init_dt_scan(fdt_pointer, __pa(fdt_pointer));
+			initial_boot_params = NULL;
+		}
+#endif
 		return;
+	}
 
 	/* Prefer to use built-in dtb, checking its legality first. */
 	if (IS_ENABLED(CONFIG_BUILTIN_DTB) && !fdt_check_header(__dtb_start))
-- 
2.25.1

[PATCH v3 2/3] LoongArch: kexec: add KHO support for ACPI-only

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

On ACPI-only systems fdt_setup() returns early when it detects ACPI,
so initial_boot_params remains NULL and the FDT-based kho_load_fdt()
path cannot be used.

machine_kexec_file.c:
- kho_load_fdt(): add an else branch that builds a minimal FDT from
  scratch (SZ_1K) containing only a /chosen node with linux,kho-fdt
  and linux,kho-scratch properties, using the libfdt creation API.
- Since DEVICE_TREE_GUID is absent from the EFI config table on
  ACPI-only systems, build a new config table with DEVICE_TREE_GUID
  appended and load it as a kexec segment.  Store the result in
  kimage_arch so machine_kexec() can switch st->tables before jumping.
- arch_kimage_file_post_load_cleanup(): free the efi_tables kvmalloc
  buffer once the kexec image has been loaded.

machine_kexec.c:
- Before jumping, update the EFI system table pointer: for FDT-based
  systems update the existing DEVICE_TREE_GUID entry; for ACPI-only
  systems switch st->tables / st->nr_tables to the new extended table.

setup.c:
- fdt_setup(): when ACPI is detected, use efi_fdt_pointer() to detect
  whether this is a KHO kexec boot.  The first kernel switches the EFI
  config table to a new one that includes a DEVICE_TREE_GUID entry
  pointing to the minimal KHO FDT.  If found, call early_init_dt_scan()
  so early_init_dt_check_kho() can consume linux,kho-fdt and
  linux,kho-scratch, then reset initial_boot_params to NULL so the rest
  of the ACPI boot path is unaffected.

kexec.h:
- Add efi_tables, efi_tables_mem, efi_tables_cnt to kimage_arch.

Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 arch/loongarch/include/asm/kexec.h         |   3 +
 arch/loongarch/kernel/machine_kexec.c      |  11 ++
 arch/loongarch/kernel/machine_kexec_file.c | 162 +++++++++++++++++++--
 arch/loongarch/kernel/setup.c              |  21 ++-
 4 files changed, 184 insertions(+), 13 deletions(-)

diff --git a/arch/loongarch/include/asm/kexec.h b/arch/loongarch/include/asm/kexec.h
index adf54bfcdd49..e1abaf40b06a 100644
--- a/arch/loongarch/include/asm/kexec.h
+++ b/arch/loongarch/include/asm/kexec.h
@@ -42,6 +42,9 @@ struct kimage_arch {
 #ifdef CONFIG_KEXEC_HANDOVER
 	void *fdt;		/* virtual address of KHO FDT segment buffer */
 	unsigned long fdt_mem;	/* physical address of KHO FDT segment */
+	void *efi_tables;		/* new EFI config table buffer (virtual) */
+	unsigned long efi_tables_mem;	/* physical address of new EFI config table */
+	unsigned long efi_tables_cnt;	/* number of entries in new EFI config table */
 #endif
 };
 
diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
index 98529c71d001..cbb7f8368843 100644
--- a/arch/loongarch/kernel/machine_kexec.c
+++ b/arch/loongarch/kernel/machine_kexec.c
@@ -313,6 +313,17 @@ void machine_kexec(struct kimage *image)
 				break;
 			}
 		}
+	} else if (internal->efi_tables_mem) {
+		/*
+		 * ACPI-only system: DEVICE_TREE_GUID was not in the original
+		 * EFI config table.  Switch to the new table that was built in
+		 * kho_load_fdt() with DEVICE_TREE_GUID appended.
+		 */
+		efi_system_table_t *st =
+			(efi_system_table_t *)TO_CACHE(systable_ptr);
+
+		st->tables    = internal->efi_tables_mem;
+		st->nr_tables = internal->efi_tables_cnt;
 	}
 #endif
 
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index bf1e8c1c7e70..c1955d991061 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -10,6 +10,7 @@
 
 #define pr_fmt(fmt) "kexec_file: " fmt
 
+#include <linux/efi.h>
 #include <linux/ioport.h>
 #include <linux/kernel.h>
 #include <linux/kexec.h>
@@ -20,6 +21,7 @@
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/vmalloc.h>
+#include <asm/addrspace.h>
 #include <asm/bootinfo.h>
 
 const struct kexec_file_ops * const kexec_file_loaders[] = {
@@ -37,6 +39,8 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 #ifdef CONFIG_KEXEC_HANDOVER
 	kvfree(image->arch.fdt);
 	image->arch.fdt = NULL;
+	kvfree(image->arch.efi_tables);
+	image->arch.efi_tables = NULL;
 #endif
 
 	return kexec_image_post_load_cleanup_default(image);
@@ -68,6 +72,13 @@ static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmpl
  * segment.  The second kernel reads linux,kho-fdt and linux,kho-scratch
  * from /chosen via early_init_dt_check_kho() and calls kho_populate().
  *
+ * On FDT-based systems (initial_boot_params != NULL), the current FDT is
+ * copied and the KHO properties are appended to /chosen.
+ *
+ * On ACPI-only systems (initial_boot_params == NULL), a minimal FDT
+ * containing only /chosen is built from scratch.  machine_kexec() updates
+ * the EFI config table DEVICE_TREE_GUID entry to point to this segment so
+ * that the second kernel's fdt_setup() can find and parse it.
  */
 static int kho_load_fdt(struct kimage *image)
 {
@@ -143,24 +154,151 @@ static int kho_load_fdt(struct kimage *image)
 		 * once the kexec image has been loaded.
 		 */
 		fdt_pack(fdt);
+	} else {
+		/*
+		 * ACPI boot: build a minimal FDT containing only /chosen with
+		 * the two KHO properties.  No system FDT is available to copy.
+		 */
 
-		kbuf.buffer	= fdt;
-		kbuf.bufsz	= fdt_totalsize(fdt);
-		kbuf.memsz	= kbuf.bufsz;
-		kbuf.buf_align	= PAGE_SIZE;
-		kbuf.mem	= KEXEC_BUF_MEM_UNKNOWN;
+		__be64 prop[2];
 
-		ret = kexec_add_buffer(&kbuf);
-		if (ret)
+		fdt_size = SZ_1K;
+		fdt = kvmalloc(fdt_size, GFP_KERNEL);
+		if (!fdt)
+			return -ENOMEM;
+
+		ret = fdt_create(fdt, fdt_size);
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_finish_reservemap(fdt);
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_begin_node(fdt, "");	/* root */
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_property_u32(fdt, "#address-cells", 2);
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_property_u32(fdt, "#size-cells", 2);
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_begin_node(fdt, "chosen");
+		if (ret < 0)
 			goto out_free;
 
-		image->arch.fdt     = fdt;
-		image->arch.fdt_mem = kbuf.mem;
-		return 0;
-	} else {
-		return -EINVAL;
+		prop[0] = cpu_to_be64(image->kho.fdt);
+		prop[1] = cpu_to_be64(PAGE_SIZE);
+		ret = fdt_property(fdt, "linux,kho-fdt", prop, sizeof(prop));
+		if (ret < 0)
+			goto out_free;
+
+		prop[0] = cpu_to_be64(image->kho.scratch->mem);
+		prop[1] = cpu_to_be64(image->kho.scratch->bufsz);
+		ret = fdt_property(fdt, "linux,kho-scratch", prop, sizeof(prop));
+		if (ret < 0)
+			goto out_free;
+
+		ret = fdt_end_node(fdt);	/* chosen */
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_end_node(fdt);	/* root */
+		if (ret < 0)
+			goto out_free;
+		ret = fdt_finish(fdt);
+		if (ret < 0)
+			goto out_free;
 	}
 
+	kbuf.buffer	= fdt;
+	kbuf.bufsz	= fdt_totalsize(fdt);
+	kbuf.memsz	= kbuf.bufsz;
+	kbuf.buf_align	= PAGE_SIZE;
+	kbuf.mem	= KEXEC_BUF_MEM_UNKNOWN;
+
+	ret = kexec_add_buffer(&kbuf);
+	if (ret)
+		goto out_free;
+
+	image->arch.fdt     = fdt;
+	image->arch.fdt_mem = kbuf.mem;
+
+	/*
+	 * On ACPI-only systems DEVICE_TREE_GUID is not in the EFI config
+	 * table, so the second kernel's efi_fdt_pointer() cannot locate the
+	 * KHO FDT.  Build a new EFI config table with DEVICE_TREE_GUID added
+	 * and load it as a kexec segment; machine_kexec() will update
+	 * st->tables / st->nr_tables to point to it before jumping.
+	 */
+
+	/*
+	 * fw_arg2 is the EFI system table physical address passed by the
+	 * firmware/bootloader.  Use it directly here because
+	 * image->arch.systable_ptr is set later in machine_kexec_prepare(),
+	 * which runs after load_other_segments() / kho_load_fdt().
+	 */
+	if (!initial_boot_params && fw_arg2) {
+		efi_system_table_t *st =
+			(efi_system_table_t *)TO_CACHE(fw_arg2);
+		efi_config_table_t *ct =
+			(efi_config_table_t *)TO_CACHE((unsigned long)st->tables);
+		unsigned long i;
+		bool found = false;
+
+		/*
+		 * Scan the original config table;
+		 * DEVICE_TREE_GUID is absent on ACPI-only systems.
+		 */
+		for (i = 0; i < st->nr_tables; i++) {
+			if (!efi_guidcmp(ct[i].guid, DEVICE_TREE_GUID)) {
+				found = true;
+				break;
+			}
+		}
+
+		if (!found) {
+			size_t old_sz = st->nr_tables * sizeof(efi_config_table_t);
+			size_t new_sz = old_sz + sizeof(efi_config_table_t);
+			efi_config_table_t *new_ct;
+			struct kexec_buf tbuf = {
+				.image		= image,
+				.buf_min	= 0,
+				.buf_max	= ULONG_MAX,
+				.top_down	= true,
+			};
+
+			/*
+			 * Allocate a new table with n+1 entries and append
+			 * the DEVICE_TREE_GUID entry.
+			 */
+			new_ct = kvmalloc(new_sz, GFP_KERNEL);
+			if (!new_ct)
+				return -ENOMEM;
+
+			memcpy(new_ct, ct, old_sz);
+			new_ct[st->nr_tables].guid  = DEVICE_TREE_GUID;
+			new_ct[st->nr_tables].table = (void *)image->arch.fdt_mem;
+
+			/* Register the new config table as a kexec segment. */
+			tbuf.buffer   = new_ct;
+			tbuf.bufsz    = new_sz;
+			tbuf.memsz    = new_sz;
+			tbuf.buf_align = sizeof(void *);
+			tbuf.mem      = KEXEC_BUF_MEM_UNKNOWN;
+
+			ret = kexec_add_buffer(&tbuf);
+			if (ret) {
+				kvfree(new_ct);
+				return ret;
+			}
+
+			image->arch.efi_tables     = new_ct;
+			image->arch.efi_tables_mem = tbuf.mem;
+			image->arch.efi_tables_cnt = st->nr_tables + 1;
+		}
+	}
+
+	return 0;
+
 out_free:
 	kvfree(fdt);
 	return ret;
diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 839b23edee87..c82067d1dc75 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -286,8 +286,27 @@ static void __init fdt_setup(void)
 	void *fdt_pointer;
 
 	/* ACPI-based systems do not require parsing fdt */
-	if (acpi_os_get_root_pointer())
+	if (acpi_os_get_root_pointer()) {
+#ifdef CONFIG_KEXEC_HANDOVER
+		/*
+		 * On a KHO kexec boot the first kernel builds a minimal FDT
+		 * containing only /chosen with linux,kho-fdt and
+		 * linux,kho-scratch, and switches the EFI config table to a
+		 * new one that includes a DEVICE_TREE_GUID entry pointing to
+		 * it.  Use efi_fdt_pointer() to detect this case.
+		 *
+		 * Call early_init_dt_scan() to let early_init_dt_check_kho()
+		 * consume the KHO data, then reset initial_boot_params so the
+		 * rest of the ACPI boot path is not confused by this FDT.
+		 */
+		fdt_pointer = efi_fdt_pointer();
+		if (fdt_pointer && !fdt_check_header(fdt_pointer)) {
+			early_init_dt_scan(fdt_pointer, __pa(fdt_pointer));
+			initial_boot_params = NULL;
+		}
+#endif
 		return;
+	}
 
 	/* Prefer to use built-in dtb, checking its legality first. */
 	if (IS_ENABLED(CONFIG_BUILTIN_DTB) && !fdt_check_header(__dtb_start))
-- 
2.25.1

[PATCH v3 3/3] selftests/kho: add LoongArch vmtest support

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

Add loongarch.conf to configure QEMU's LoongArch virt machine with a
la464 CPU, enable the 8250 serial console, and set the kernel image
to vmlinux.efi.  Extend vmtest.sh to recognise loongarch64 as a
supported target and map it to the 'loongarch' kernel arch name.

QEMU's LoongArch virt machine provides no ACPI tables and relies on
FDT to describe hardware.  Without 'earlycon' on the kernel command
line, the FDT is not scanned for a console UART, no output reaches
the console, and vmtest.sh's console log stays empty causing the test
to always fail.  Add 'earlycon' to KERNEL_CMDLINE in loongarch.conf.

QEMU's LoongArch virt machine has no i8042 PS/2 controller.  When PNP
detection finds nothing, i8042_init() falls back to probing the ports
directly.  On LoongArch the I/O ports are memory-mapped, and the i8042
port addresses are not backed by any device on the virt machine, so
i8042_flush() takes a page fault and the kernel panics:

  i8042: PNP: No PS/2 controller found.
  i8042: Probing ports directly.
  CPU 0 Unable to handle kernel paging request at virtual address ffff800000008064
  ERA: i8042_flush+0x50/0x198
   RA: i8042_init+0x2a8/0x35c
  Kernel panic - not syncing: Attempted to kill init!

Disable SERIO_I8042 and its dependents (KEYBOARD_ATKBD, MOUSE_PS2) in
the QEMU_KCONFIG fragment to prevent the driver from being built.
All three options are scoped to loongarch.conf; no other architecture
is affected.

QEMU provides no EFI runtime services on LoongArch, so machine_restart()
falls through to an infinite idle loop after kexec.  Set QEMU_TIMEOUT=120
in loongarch.conf so vmtest.sh wraps the QEMU invocation with timeout(1),
which terminates QEMU after 120 seconds if it does not exit on its own.
Architectures that do not set QEMU_TIMEOUT are unaffected.

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 tools/testing/selftests/kho/loongarch.conf | 13 ++++++++++++
 tools/testing/selftests/kho/vmtest.sh      | 23 +++++++++++++++-------
 2 files changed, 29 insertions(+), 7 deletions(-)
 create mode 100644 tools/testing/selftests/kho/loongarch.conf

diff --git a/tools/testing/selftests/kho/loongarch.conf b/tools/testing/selftests/kho/loongarch.conf
new file mode 100644
index 000000000000..68727654578d
--- /dev/null
+++ b/tools/testing/selftests/kho/loongarch.conf
@@ -0,0 +1,13 @@
+QEMU_CMD="qemu-system-loongarch64 -M virt -cpu la464"
+QEMU_KCONFIG="
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+# CONFIG_KEYBOARD_ATKBD is not set
+# CONFIG_MOUSE_PS2 is not set
+# CONFIG_SERIO_I8042 is not set
+"
+KERNEL_IMAGE="vmlinux.efi"
+KERNEL_CMDLINE="console=ttyS0 earlycon"
+# QEMU never exits after kexec on LoongArch (no EFI runtime services);
+# give the test a fixed time limit and let timeout(1) terminate QEMU.
+QEMU_TIMEOUT=120
diff --git a/tools/testing/selftests/kho/vmtest.sh b/tools/testing/selftests/kho/vmtest.sh
index 49fdac8e8b15..918698b6dd2a 100755
--- a/tools/testing/selftests/kho/vmtest.sh
+++ b/tools/testing/selftests/kho/vmtest.sh
@@ -21,7 +21,7 @@ Options:
 	-d)	path to the kernel build directory
 	-j)	number of jobs for compilation, similar to -j in make
 	-t)	run test for target_arch, requires CROSS_COMPILE set
-		supported targets: aarch64, x86_64
+		supported targets: aarch64, x86_64, loongarch64
 	-h)	display this help
 EOF
 }
@@ -107,12 +107,20 @@ function run_qemu() {
 
 	cmdline="$cmdline kho=on panic=-1"
 
-	$qemu_cmd -m 1G -smp 2 -no-reboot -nographic -nodefaults \
-		  -accel kvm -accel hvf -accel tcg  \
-		  -serial file:"$serial" \
-		  -append "$cmdline" \
-		  -kernel "$kernel" \
-		  -initrd "$initrd"
+	local qemu_args=(
+		-m 1G -smp 2 -no-reboot -nographic -nodefaults
+		-accel kvm -accel hvf -accel tcg
+		-serial file:"$serial"
+		-append "$cmdline"
+		-kernel "$kernel"
+		-initrd "$initrd"
+	)
+
+	if [[ -n "${QEMU_TIMEOUT:-}" ]]; then
+		timeout "$QEMU_TIMEOUT" $qemu_cmd "${qemu_args[@]}" || true
+	else
+		$qemu_cmd "${qemu_args[@]}"
+	fi
 
 	grep "KHO restore succeeded" "$serial" &> /dev/null || fail "KHO failed"
 }
@@ -123,6 +131,7 @@ function target_to_arch() {
 	case $target in
 	     aarch64) echo "arm64" ;;
 	     x86_64) echo "x86" ;;
+	     loongarch64) echo "loongarch" ;;
 	     *) skip "architecture $target is not supported"
 	esac
 }
-- 
2.25.1

Re: [PATCH v3 0/3] LoongArch: add KHO support and selftests

[George Guo]

Hi Mike, Huacai,

Gentle ping on this v3. In the v2 review you mentioned you'd wait for
v3 for a more detailed look -- v3 addresses both points (folded the two
selftest patches into one, and replaced the LoongArch-specific kill
loop with timeout(1), with the timeout value set per-arch in the conf).

No rush, just making sure it didn't slip through the cracks. Happy to
spin a rebase if it's gone stale.

Thanks!

--
George

Re: [PATCH v3 0/3] LoongArch: add KHO support and selftests

[Pratyush Yadav]

On Tue, Jun 09 2026, George Guo wrote:

> Hi Mike, Huacai,
>
> Gentle ping on this v3. In the v2 review you mentioned you'd wait for
> v3 for a more detailed look -- v3 addresses both points (folded the two
> selftest patches into one, and replaced the LoongArch-specific kill
> loop with timeout(1), with the timeout value set per-arch in the conf).
>
> No rush, just making sure it didn't slip through the cracks. Happy to
> spin a rebase if it's gone stale.

It is on my review list, and I hope to get to it soon. But no promises
unfortunately.

-- 
Regards,
Pratyush Yadav