[PATCH v5 0/5] LoongArch: add KHO support and selftests

[PATCH v5 0/5] LoongArch: add KHO support and selftests

[George Guo]

This series enables Kexec HandOver (KHO) on 64-bit LoongArch and adds
LoongArch coverage to the KHO QEMU selftest.  KHO is the remaining
architecture gate needed by Live Update (LUO) on LoongArch.

The transport is the central problem.  Arm64 and riscv can pass the KHO
state FDT and scratch area through properties under /chosen in a boot
FDT.  LoongArch boots through EFI without a boot FDT, so that path is not
available.

EFI KHO channel:

v5 reworks the EFI transport following Pratyush's and Huacai's reviews
[1, 2].  Instead of rebuilding the EFI configuration table in
LoongArch code and switching st->tables before kexec, the common EFI stub
allocates and installs a persistent table under
LINUX_EFI_KEXEC_HANDOVER_GUID.  This follows the model used by
LINUX_EFI_MEMRESERVE_TABLE_GUID.

The common EFI table parser reserves the stub-allocated table, reads it
during early boot, and calls kho_populate().  An early initcall keeps the
table persistently mapped so it can also be updated on the crash kexec
path.  The implementation is architecture-independent; LoongArch only
selects EFI_KHO when KEXEC_HANDOVER is enabled.

The EFI table is global, but kexec can keep separate normal and crash
images and can replace a loaded candidate.  Updating the table while a
candidate image is being loaded could therefore leave it pointing at a
failed candidate while the previously installed image remains the one
that will be executed.  v5 records the KHO data in struct kimage and
synchronizes the channel from the image selected for execution.  Images
without KHO data, including legacy and crash images, clear the channel so
the next kernel boots cold rather than reviving stale state.

The GUID name is changed to LINUX_EFI_KEXEC_HANDOVER_GUID as suggested by
Huacai and Pratyush [3].  Existing x86 KHO support continues to use its
setup_data transport.  Besides supporting non-UEFI boot, that entry is
consumed by the x86 decompressor before normal EFI table parsing, so KASLR
only uses KHO scratch areas and does not overwrite preserved memory.  The
new channel is installed by the generic EFI-stub entry path and relies on
EFI_GENERIC_STUB, which x86 does not select.  Moving x86 would therefore
require installing the table from the x86-specific EFI stub and scanning it
in the decompressor, not just selecting EFI_KHO.

LoongArch enablement and build fix:

The architecture patch now only enables ARCH_SUPPORTS_KEXEC_HANDOVER and
selects the generic EFI channel.  No LoongArch setup reader, kexec writer,
or EFI system-table replacement remains.

The linux/mm.h build fix is moved from luo_session.c to kho_block.c, where
the virt_to_phys() and phys_to_virt() calls reside after the liveupdate
refactoring.  This addresses Pratyush's review [4].  Adding linux/mm.h to
asm/io.h was previously attempted, but creates an include cycle under
CONFIG_KFENCE [5].  The fix precedes LoongArch enablement so every
intermediate commit builds with CONFIG_KFENCE=y.

Selftest:

The LoongArch vmtest boots vmlinux.efi through EDK2 because the initial
EFI stub invocation installs the channel being tested.  QEMU_EFI can
override the firmware filename for distributions that install it under a
different name or path.

CONFIG_ACPI_SPCR_TABLE lets the bare earlycon parameter obtain the UART
description from EDK2's SPCR table.  CONFIG_PCI_HOST_GENERIC keeps i8042
enabled while ensuring that the QEMU virt machine's PCI I/O space is
mapped before the legacy fallback probe, addressing Huacai's concern that
the same kernel configuration should remain usable for hosts and guests.

With EFI runtime reset services available, panic=-1 and QEMU's existing
-no-reboot option terminate the test normally.  The generic QEMU runner
therefore remains unchanged and does not mask failures by forcibly
terminating QEMU after a timeout.

The LoongArch vmtest uses the default KHO scratch-sizing path.  This
series is based on the generic fix that calculates per-node scratch sizes
before scratch allocation [6].

The KHO vmtest passes on:

  * LoongArch with KVM using QEMU_EFI.fd from edk2-loongarch64.
  * x86_64 with KVM, as regression coverage for the generic kexec/KHO
    changes.

Patch layout:

  1. Add the generic EFI KHO channel and its ABI.
  2. Synchronize the channel from the selected image at execution.
  3. Fix the kho_block.c header dependency exposed by LoongArch/KFENCE.
  4. Enable KHO on 64-bit LoongArch through the generic EFI channel.
  5. Add LoongArch to the KHO QEMU selftest.

Changes since v4:

  * Allocate and install the KHO table from the common EFI stub, following
    the EFI memreserve-table model (Pratyush).
  * Parse, reserve, map, and update the channel in generic EFI code; remove
    the LoongArch-specific reader, writer, and st->tables replacement
    (Pratyush, Huacai).
  * Synchronize the global channel at execution rather than image load;
    clear it for cold and crash images and use the scratch payload size.
  * Rename the GUID to LINUX_EFI_KEXEC_HANDOVER_GUID (Huacai, Pratyush).
  * Move the linux/mm.h include from luo_session.c to the actual caller,
    kho_block.c, and place the fix before architecture enablement
    (Pratyush, Huacai).
  * Boot the vmtest through EDK2, allow QEMU_EFI to override the firmware,
    and use vmlinux.efi to exercise the EFI stub and channel.
  * Keep i8042 enabled and select PCI_HOST_GENERIC instead of disabling
    the host configuration in the selftest (Huacai).
  * Enable ACPI_SPCR_TABLE and use the SPCR-provided early console.
  * Exercise the default KHO scratch-sizing path in the LoongArch vmtest;
    depend on the separately posted generic sizing fix [6].
  * Drop the generic QEMU timeout now that EFI runtime reset services make
    the LoongArch guest terminate normally.
  * Rebase onto Linux 7.3-rc1.

[1] Pratyush Yadav:
    https://lore.kernel.org/r/2vxzo6f96fmn.fsf@kernel.org/
[2] Huacai Chen:
    https://lore.kernel.org/r/CAAhV-H4PKRNCa4g=6TGepP+trtM82JiMoWgVr3O7PqbZYP9uGw@mail.gmail.com/
[3] https://lore.kernel.org/r/2vxzse4m54nz.fsf@kernel.org/
[4] https://lore.kernel.org/r/2vxzfr0l6fam.fsf@kernel.org/
[5] https://lore.kernel.org/r/202605211925.DbDvQ6ii-lkp@intel.com/
[6] https://lore.kernel.org/loongarch/20260904025101.9959-1-dongtai.guo@linux.dev/

Previous version:

v4: https://lore.kernel.org/loongarch/20260807103714.33074-1-dongtai.guo@linux.dev/

George Guo (5):
  efi: add a KHO configuration table channel
  liveupdate: synchronize EFI KHO channel at execution
  liveupdate: kho_block: include linux/mm.h for virt/phys translation
  LoongArch: enable kexec handover (KHO)
  selftests/kho: add LoongArch vmtest support

 arch/loongarch/Kconfig                     |  4 ++
 drivers/firmware/efi/Kconfig               | 12 ++++
 drivers/firmware/efi/efi.c                 | 78 ++++++++++++++++++++++
 drivers/firmware/efi/libstub/efi-stub.c    | 25 +++++++
 include/linux/efi.h                        | 36 ++++++++++
 kernel/crash_core.c                        |  7 ++
 kernel/kexec_core.c                        |  5 ++
 kernel/kexec_internal.h                    |  3 +
 kernel/liveupdate/kexec_handover.c         | 33 +++++++++
 kernel/liveupdate/kho_block.c              |  1 +
 tools/testing/selftests/kho/loongarch.conf | 11 +++
 tools/testing/selftests/kho/vmtest.sh      |  3 +-
 12 files changed, 217 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/kho/loongarch.conf


base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
prerequisite-patch-id: a2f06addb17cc379b9f98674f087a1642588dc6e
-- 
2.53.0

[PATCH v5 1/5] efi: add a KHO configuration table channel

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

Add an architecture-agnostic EFI configuration table channel for kexec
handover (KHO): a LINUX_EFI_KEXEC_HANDOVER_GUID table entry pointing at
a struct linux_efi_kho_data that carries the KHO state FDT and scratch
area addresses from one kernel to the next.

This is the channel for architectures that boot through EFI without a
device tree (e.g. LoongArch), where the /chosen linux,kho-fdt and
linux,kho-scratch properties read by early_init_dt_check_kho() are not
available.  Architectures with a boot FDT (arm64, riscv) keep using the
FDT path and do not select this.

The design mirrors the LINUX_EFI_MEMRESERVE_TABLE_GUID channel:

  - The EFI stub allocates and installs the table once at boot
    (install_kho_table(), next to install_memreserve_table()), so the
    config table entry is inherited across kexec for free.

  - The reader is a common_tables[] entry in
    efi_config_parse_tables().  It reserves the stub-allocated table
    with memblock_reserve(), the same way the memreserve entries are
    reserved there, so the table is neither handed out by the buddy
    allocator nor placed on by kexec segments.  It then maps the table
    and calls kho_populate().  No arch-specific setup.c hook is
    needed.

  - efi_kho_update() rewrites the table contents in place before a
    kexec; the config table array is never rebuilt and st->tables is
    never switched, unlike the per-arch approach it replaces.  The
    table stays persistently mapped from an early_initcall, the same
    way the memreserve root is, so the update also works on the crash
    kexec path.

Gated behind CONFIG_EFI_KHO, selected by architectures that use this
channel.

Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 drivers/firmware/efi/Kconfig            | 12 ++++
 drivers/firmware/efi/efi.c              | 78 +++++++++++++++++++++++++
 drivers/firmware/efi/libstub/efi-stub.c | 25 ++++++++
 include/linux/efi.h                     | 36 ++++++++++++
 4 files changed, 151 insertions(+)

diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 29e0729299f5..d6c1372484b4 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -314,6 +314,18 @@ config EFI_SBAT_FILE
 
 	  If unsure, leave blank.
 
+config EFI_KHO
+	bool
+	depends on EFI_STUB && EFI_GENERIC_STUB && KEXEC_HANDOVER
+	help
+	  Carry the KHO state (the KHO state FDT and the scratch area) from
+	  one kernel to the next across kexec via an EFI configuration table
+	  entry under LINUX_EFI_KEXEC_HANDOVER_GUID, for architectures that
+	  boot through EFI without a device tree (e.g. LoongArch).
+
+	  Architectures with a boot FDT (arm64, riscv) use the /chosen FDT
+	  path instead and do not select this.
+
 endmenu
 
 config UEFI_CPER
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 0327a39d31fa..6380cfab1493 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -24,6 +24,7 @@
 #include <linux/initrd.h>
 #include <linux/io.h>
 #include <linux/kexec.h>
+#include <linux/kexec_handover.h>
 #include <linux/platform_device.h>
 #include <linux/random.h>
 #include <linux/reboot.h>
@@ -62,6 +63,9 @@ unsigned long __ro_after_init efi_rng_seed = EFI_INVALID_TABLE_ADDR;
 static unsigned long __initdata mem_reserve = EFI_INVALID_TABLE_ADDR;
 static unsigned long __initdata rt_prop = EFI_INVALID_TABLE_ADDR;
 static unsigned long __initdata initrd = EFI_INVALID_TABLE_ADDR;
+#ifdef CONFIG_EFI_KHO
+static unsigned long __ro_after_init efi_kho_table_phys = EFI_INVALID_TABLE_ADDR;
+#endif
 
 extern unsigned long primary_display_table;
 
@@ -629,6 +633,9 @@ static const efi_config_table_type_t common_tables[] __initconst = {
 	{EFI_TCG2_FINAL_EVENTS_TABLE_GUID,	&efi.tpm_final_log,	"TPMFinalLog"	},
 	{EFI_CC_FINAL_EVENTS_TABLE_GUID,	&efi.tpm_final_log,	"CCFinalLog"	},
 	{LINUX_EFI_MEMRESERVE_TABLE_GUID,	&mem_reserve,		"MEMRESERVE"	},
+#ifdef CONFIG_EFI_KHO
+	{LINUX_EFI_KEXEC_HANDOVER_GUID,		&efi_kho_table_phys,	"KHO"		},
+#endif
 	{LINUX_EFI_INITRD_MEDIA_GUID,		&initrd,		"INITRD"	},
 	{EFI_RT_PROPERTIES_TABLE_GUID,		&rt_prop,		"RTPROP"	},
 #ifdef CONFIG_OVMF_DEBUG_LOG
@@ -806,6 +813,31 @@ int __init efi_config_parse_tables(const efi_config_table_t *config_tables,
 		}
 	}
 
+#ifdef CONFIG_EFI_KHO
+	if (efi_kho_table_phys != EFI_INVALID_TABLE_ADDR) {
+		struct linux_efi_kho_data *kho;
+
+		/*
+		 * Reserve the stub-allocated table so it is neither handed
+		 * out by the buddy allocator nor placed on by kexec
+		 * segments, mirroring the memreserve handling above.  This
+		 * runs on every boot, so it also protects the table in the
+		 * next kernel until it reads it.
+		 */
+		memblock_reserve(efi_kho_table_phys, sizeof(*kho));
+
+		kho = early_memremap(efi_kho_table_phys, sizeof(*kho));
+		if (kho) {
+			if (kho->fdt_addr)
+				kho_populate((phys_addr_t)kho->fdt_addr,
+					     kho->fdt_size,
+					     (phys_addr_t)kho->scratch_addr,
+					     kho->scratch_size);
+			early_memunmap(kho, sizeof(*kho));
+		}
+	}
+#endif
+
 	if (rt_prop != EFI_INVALID_TABLE_ADDR) {
 		efi_rt_properties_table_t *tbl;
 
@@ -1171,6 +1203,52 @@ static int __init efi_memreserve_root_init(void)
 }
 early_initcall(efi_memreserve_root_init);
 
+#ifdef CONFIG_EFI_KHO
+static struct linux_efi_kho_data *efi_kho_table __ro_after_init;
+
+static int __init efi_kho_table_init(void)
+{
+	if (efi_kho_table_phys == EFI_INVALID_TABLE_ADDR)
+		return 0;
+
+	/*
+	 * Keep a persistent mapping of the table, the same way
+	 * efi_memreserve_root_init() keeps the memreserve root mapped:
+	 * efi_kho_update() is also called on the crash kexec path, where
+	 * memremap() is no longer an option.
+	 */
+	efi_kho_table = memremap(efi_kho_table_phys, sizeof(*efi_kho_table),
+				 MEMREMAP_WB);
+	WARN_ON_ONCE(!efi_kho_table);
+
+	return 0;
+}
+early_initcall(efi_kho_table_init);
+
+/*
+ * Update the KHO config table in place before a kexec, so the next kernel
+ * finds the current handover state.  Mirrors efi_mem_reserve_persistent():
+ * the config table entry was installed once by the EFI stub and is inherited
+ * across kexec, so only the table contents are rewritten here -- the config
+ * table array is never rebuilt and st->tables is never switched.
+ */
+int efi_kho_update(phys_addr_t fdt_addr, u64 fdt_size,
+		   phys_addr_t scratch_addr, u64 scratch_size)
+{
+	struct linux_efi_kho_data *kho = efi_kho_table;
+
+	if (!kho)
+		return -ENODEV;
+
+	kho->fdt_addr		= fdt_addr;
+	kho->fdt_size		= fdt_size;
+	kho->scratch_addr	= scratch_addr;
+	kho->scratch_size	= scratch_size;
+
+	return 0;
+}
+#endif
+
 #ifdef CONFIG_KEXEC
 static int update_efi_random_seed(struct notifier_block *nb,
 				  unsigned long code, void *unused)
diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c
index 42d6073bcd06..751f46280433 100644
--- a/drivers/firmware/efi/libstub/efi-stub.c
+++ b/drivers/firmware/efi/libstub/efi-stub.c
@@ -100,6 +100,29 @@ static void install_memreserve_table(void)
 		efi_err("Failed to install memreserve config table!\n");
 }
 
+static void install_kho_table(void)
+{
+#ifdef CONFIG_EFI_KHO
+	struct linux_efi_kho_data *kho;
+	efi_guid_t kho_table_guid = LINUX_EFI_KEXEC_HANDOVER_GUID;
+	efi_status_t status;
+
+	status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, sizeof(*kho),
+			     (void **)&kho);
+	if (status != EFI_SUCCESS) {
+		efi_err("Failed to allocate KHO config table!\n");
+		return;
+	}
+
+	*kho = (struct linux_efi_kho_data){};
+
+	status = efi_bs_call(install_configuration_table, &kho_table_guid,
+			     kho);
+	if (status != EFI_SUCCESS)
+		efi_err("Failed to install KHO config table!\n");
+#endif
+}
+
 static u32 get_supported_rt_services(void)
 {
 	const efi_rt_properties_table_t *rt_prop_table;
@@ -180,6 +203,8 @@ efi_status_t efi_stub_common(efi_handle_t handle,
 
 	install_memreserve_table();
 
+	install_kho_table();
+
 	status = efi_boot_kernel(handle, image, image_addr, cmdline_ptr);
 
 	free_primary_display(dpy);
diff --git a/include/linux/efi.h b/include/linux/efi.h
index aa15ff88539b..564b3cbd5ccb 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -422,6 +422,7 @@ void efi_native_runtime_setup(void);
 #define LINUX_EFI_COCO_SECRET_AREA_GUID		EFI_GUID(0xadf956ad, 0xe98c, 0x484c,  0xae, 0x11, 0xb5, 0x1c, 0x7d, 0x33, 0x64, 0x47)
 #define LINUX_EFI_BOOT_MEMMAP_GUID		EFI_GUID(0x800f683f, 0xd08b, 0x423a,  0xa2, 0x93, 0x96, 0x5c, 0x3c, 0x6f, 0xe2, 0xb4)
 #define LINUX_EFI_UNACCEPTED_MEM_TABLE_GUID	EFI_GUID(0xd5d1de3c, 0x105c, 0x44f9,  0x9e, 0xa9, 0xbc, 0xef, 0x98, 0x12, 0x00, 0x31)
+#define LINUX_EFI_KEXEC_HANDOVER_GUID		EFI_GUID(0xc941b6c7, 0x7b3f, 0x4af6,  0x9e, 0x50, 0xfc, 0xb3, 0xa8, 0x86, 0x8a, 0x17)
 
 #define RISCV_EFI_BOOT_PROTOCOL_GUID		EFI_GUID(0xccd15fec, 0x6f73, 0x4eec,  0x83, 0x95, 0x3e, 0x69, 0xe4, 0xb9, 0x40, 0xbf)
 
@@ -1273,6 +1274,41 @@ struct linux_efi_memreserve {
 
 void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size);
 
+#ifdef CONFIG_EFI_KHO
+/*
+ * The LINUX_EFI_KEXEC_HANDOVER_GUID config table points to this structure.
+ * It carries the kexec handover (KHO) state from the current kernel to the
+ * next one: the addresses of the KHO state FDT and of the scratch area.
+ *
+ * This is the handover channel for architectures that boot through EFI
+ * without a device tree (e.g. LoongArch), where the /chosen linux,kho-fdt
+ * and linux,kho-scratch properties read by early_init_dt_check_kho() are not
+ * available.  The EFI stub allocates and installs the table once at boot;
+ * the current kernel updates its contents before a kexec, and the next
+ * kernel reads it back and calls kho_populate().
+ *
+ * The layout is an ABI between the two kernels and carries no version
+ * field: an incompatible change must use a new GUID.  The handover payload
+ * itself is versioned separately by the compatible string of the KHO state
+ * FDT, which kho_populate() checks.
+ */
+struct linux_efi_kho_data {
+	u64 fdt_addr;
+	u64 fdt_size;
+	u64 scratch_addr;
+	u64 scratch_size;
+} __packed;
+
+int efi_kho_update(phys_addr_t fdt_addr, u64 fdt_size,
+		   phys_addr_t scratch_addr, u64 scratch_size);
+#else
+static inline int efi_kho_update(phys_addr_t fdt_addr, u64 fdt_size,
+				 phys_addr_t scratch_addr, u64 scratch_size)
+{
+	return 0;
+}
+#endif
+
 /*
  * The LINUX_EFI_MOK_VARIABLE_TABLE_GUID config table can be provided
  * to the kernel by an EFI boot loader. The table contains a packed
-- 
2.53.0

[PATCH v5 2/5] liveupdate: synchronize EFI KHO channel at execution

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

The EFI KHO configuration table is a global channel. Updating it while
a candidate kexec image is still being loaded can leave the channel
pointing at the failed candidate even though the previous image remains
installed. Synchronize it instead from the image selected for execution.

Use the actual scratch payload size rather than its page-aligned segment
size, and propagate update failures before live-update serialization.
Keep clearing the channel for cold and crash images best-effort.

Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 kernel/crash_core.c                |  7 +++++++
 kernel/kexec_core.c                |  5 +++++
 kernel/kexec_internal.h            |  3 +++
 kernel/liveupdate/kexec_handover.c | 33 ++++++++++++++++++++++++++++++
 4 files changed, 48 insertions(+)

diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 2b36aa9fade0..6166ce4203d3 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -138,6 +138,13 @@ void __noclone __crash_kexec(struct pt_regs *regs)
 		if (kexec_crash_image) {
 			struct pt_regs fixed_regs;
 
+			/*
+			 * A crash image carries no KHO state: clear the
+			 * transport so the crash kernel boots cold instead
+			 * of reviving from stale state.
+			 */
+			(void)kho_sync_channel(kexec_crash_image);
+
 			crash_setup_regs(&fixed_regs, regs);
 			crash_save_vmcoreinfo();
 			machine_crash_shutdown(&fixed_regs);
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index dc770b9a6d05..147f5b5b23d4 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1146,6 +1146,11 @@ int kernel_kexec(void)
 		goto Unlock;
 	}
 
+	/* Synchronize the handover transport with the image being executed. */
+	error = kho_sync_channel(kexec_image);
+	if (error)
+		goto Unlock;
+
 	if (!kexec_image->preserve_context) {
 		error = liveupdate_reboot();
 		if (error)
diff --git a/kernel/kexec_internal.h b/kernel/kexec_internal.h
index 228bb88c018b..4d4c2290e85c 100644
--- a/kernel/kexec_internal.h
+++ b/kernel/kexec_internal.h
@@ -46,6 +46,7 @@ struct kexec_buf;
 int kho_locate_mem_hole(struct kexec_buf *kbuf,
 			int (*func)(struct resource *, void *));
 int kho_fill_kimage(struct kimage *image);
+int kho_sync_channel(struct kimage *image);
 #else
 static inline int kho_locate_mem_hole(struct kexec_buf *kbuf,
 				      int (*func)(struct resource *, void *))
@@ -54,5 +55,7 @@ static inline int kho_locate_mem_hole(struct kexec_buf *kbuf,
 }
 
 static inline int kho_fill_kimage(struct kimage *image) { return 0; }
+
+static inline int kho_sync_channel(struct kimage *image) { return 0; }
 #endif /* CONFIG_KEXEC_HANDOVER */
 #endif /* LINUX_KEXEC_INTERNAL_H */
diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index 39f489a258d9..3aa5c66dfc6d 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -14,6 +14,7 @@
 #include <linux/cma.h>
 #include <linux/kmemleak.h>
 #include <linux/count_zeros.h>
+#include <linux/efi.h>
 #include <linux/kasan.h>
 #include <linux/kexec.h>
 #include <linux/kexec_handover.h>
@@ -2074,6 +2075,38 @@ int kho_fill_kimage(struct kimage *image)
 	return 0;
 }
 
+/*
+ * Synchronize the handover transport with the image that is about to be
+ * executed.  The EFI config table channel is global, while kexec keeps
+ * separate images for a normal reboot and for crash.  Write the state of the
+ * selected image immediately before it is executed, rather than while a
+ * candidate image is being loaded, so a failed replacement cannot leave the
+ * channel pointing at that failed image.
+ *
+ * An image loaded through the legacy kexec_load() syscall, a crash image, or
+ * an image loaded while KHO is disabled carries no handover state.  Clear the
+ * channel for those images so the next kernel boots cold instead of reviving
+ * from stale state.  Clearing is best-effort because an absent channel cannot
+ * affect a cold boot.
+ */
+int kho_sync_channel(struct kimage *image)
+{
+	int err;
+
+	if (!image->kho.fdt || !image->kho.scratch) {
+		efi_kho_update(0, 0, 0, 0);
+		return 0;
+	}
+
+	err = efi_kho_update(image->kho.fdt, PAGE_SIZE,
+			     image->kho.scratch->mem,
+			     image->kho.scratch->bufsz);
+	if (err)
+		pr_warn("failed to update EFI config table: %d\n", err);
+
+	return err;
+}
+
 static int kho_walk_scratch(struct kexec_buf *kbuf,
 			    int (*func)(struct resource *, void *))
 {
-- 
2.53.0

[PATCH v5 3/5] liveupdate: kho_block: include linux/mm.h for virt/phys translation

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

kho_block.c calls virt_to_phys() and phys_to_virt(). On LoongArch with
CONFIG_KFENCE=y, these macros (in arch/loongarch/include/asm/io.h) expand
to offset_in_page() and page_address(), both declared in <linux/mm.h>.

Since kho_block.c does not include <linux/mm.h>, the translation unit
fails to build with CONFIG_KFENCE=y:

  asm/io.h: error: implicit declaration of function 'offset_in_page'
  asm/io.h: error: implicit declaration of function 'page_address'

Add the missing include to fix these build errors.

This is the same root cause as the luo_session.c build fix previously
acked by Mike Rapoport [1]; the virt_to_phys()/phys_to_virt() calls have
since been refactored from luo_session.c into kho_block.c, so the fix
moves with it.

[1] https://lore.kernel.org/r/ai5nYlbERQBXRHSp@kernel.org/

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 kernel/liveupdate/kho_block.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/liveupdate/kho_block.c b/kernel/liveupdate/kho_block.c
index 0d2a342ef422..0d56891b2f4c 100644
--- a/kernel/liveupdate/kho_block.c
+++ b/kernel/liveupdate/kho_block.c
@@ -25,6 +25,7 @@
 #include <linux/kho/abi/block.h>
 #include <linux/kho_block.h>
 #include <linux/slab.h>
+#include <linux/mm.h>
 
 /*
  * Safeguard limit for the number of serialization blocks. This is used to
-- 
2.53.0

[PATCH v5 4/5] LoongArch: enable kexec handover (KHO)

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

Enable ARCH_SUPPORTS_KEXEC_HANDOVER for 64-bit LoongArch.  It selects
EFI_KHO whenever KEXEC_HANDOVER is enabled, so LoongArch uses the
architecture-agnostic EFI configuration table channel
(LINUX_EFI_KEXEC_HANDOVER_GUID) introduced by this series to carry the
KHO state across kexec.

LoongArch boots through EFI without a device tree, so it cannot use the
/chosen FDT path that arm64 and riscv use; the EFI configuration table
channel is its handover transport.  No arch-specific setup.c reader or
machine_kexec_file.c writer is needed -- both live in the generic EFI
code.

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 | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index a21f51e5815e..5eaa65578d58 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -685,6 +685,10 @@ config ARCH_SUPPORTS_KEXEC
 config ARCH_SUPPORTS_KEXEC_FILE
 	def_bool 64BIT
 
+config ARCH_SUPPORTS_KEXEC_HANDOVER
+	def_bool 64BIT && EFI_STUB
+	select EFI_KHO if KEXEC_HANDOVER
+
 config ARCH_SELECTS_KEXEC_FILE
 	def_bool 64BIT
 	depends on KEXEC_FILE
-- 
2.53.0

[PATCH v5 5/5] selftests/kho: add LoongArch vmtest support

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

Add loongarch.conf to configure QEMU's LoongArch virtual machine with a
la464 CPU, an 8250 serial console, and the generic PCI host controller.
Extend vmtest.sh to recognize loongarch64 as a supported target and map
it to the loongarch kernel architecture name.

Boot vmlinux.efi through EFI firmware.  The KHO configuration table
channel is installed by the EFI stub during the initial boot, so direct
kernel boot bypasses the path that this test needs to exercise.  QEMU_EFI
defaults to the firmware shipped under /usr/share/edk2/loongarch64/ and
can be overridden for distributions that install it under a different
path, such as Debian's qemu-efi-loongarch64 package.

QEMU's LoongArch virt machine has no i8042 controller.  Enable the generic
PCI host so its I/O space is mapped before the i8042 fallback probe
accesses the legacy ports.  This avoids disabling the i8042 options and
allows the same kernel configuration to remain usable on physical hosts.

Enable ACPI_SPCR_TABLE so the bare earlycon parameter can obtain the UART
type, MMIO address and baud rate from the SPCR table installed by EDK2.
Unlike on x86, ACPI_SPCR_TABLE does not default to enabled on LoongArch.
Without it, no early console is registered for the EFI firmware boot path,
and vmtest cannot observe the early kernel output in its serial log.

The KHO vmtest requires CONFIG_DEFERRED_STRUCT_PAGE_INIT=y, which
depends on SPARSEMEM.  Select CONFIG_SPARSEMEM_MANUAL=y to satisfy the
dependency on LoongArch.

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 | 11 +++++++++++
 tools/testing/selftests/kho/vmtest.sh      |  3 ++-
 2 files changed, 13 insertions(+), 1 deletion(-)
 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..36153b03c4ef
--- /dev/null
+++ b/tools/testing/selftests/kho/loongarch.conf
@@ -0,0 +1,11 @@
+QEMU_EFI="${QEMU_EFI:-/usr/share/edk2/loongarch64/QEMU_EFI.fd}"
+QEMU_CMD="qemu-system-loongarch64 -M virt -cpu la464 -bios $QEMU_EFI"
+QEMU_KCONFIG="
+CONFIG_ACPI_SPCR_TABLE=y
+CONFIG_PCI_HOST_GENERIC=y
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_SPARSEMEM_MANUAL=y
+"
+KERNEL_IMAGE="vmlinux.efi"
+KERNEL_CMDLINE="console=ttyS0 earlycon"
diff --git a/tools/testing/selftests/kho/vmtest.sh b/tools/testing/selftests/kho/vmtest.sh
index 0014bd76e88d..d05ba0734b25 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, loongarch64, x86_64
 	-h)	display this help
 EOF
 }
@@ -126,6 +126,7 @@ function target_to_arch() {
 
 	case $target in
 	     aarch64) echo "arm64" ;;
+	     loongarch64) echo "loongarch" ;;
 	     x86_64) echo "x86" ;;
 	     *) skip "architecture $target is not supported"
 	esac
-- 
2.53.0