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([2601:647:6881:9060:bc87:d8fe:3e55:7ffb]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b6a76b6f302sm4332032a12.38.2025.10.18.23.17.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 18 Oct 2025 23:17:03 -0700 (PDT) From: Cong Wang To: linux-kernel@vger.kernel.org Cc: jiri@resnulli.us, stefanha@redhat.com, multikernel@lists.linux.dev, pasha.tatashin@soleen.com, Cong Wang , Andrew Morton , Baoquan He , Alexander Graf , Mike Rapoport , Changyuan Lyu , kexec@lists.infradead.org, linux-mm@kvack.org Subject: [RFC Patch v2 07/16] kexec: Implement dynamic kimage tracking Date: Sat, 18 Oct 2025 23:16:21 -0700 Message-Id: <20251019061631.2235405-8-xiyou.wangcong@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20251019061631.2235405-1-xiyou.wangcong@gmail.com> References: <20251019061631.2235405-1-xiyou.wangcong@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Cong Wang Replace static kexec_image and kexec_crash_image globals with a dynamic linked list infrastructure to support multiple kernel images. This change enables multikernel functionality while maintaining backward compatibility. Key changes: - Add list_head member to kimage structure for chaining - Implement thread-safe linked list management with global mutex - Update kexec load/unload logic to use list-based APIs for multikernel - Add helper functions for finding and managing multiple kimages - Preserve existing kexec_image/kexec_crash_image pointers for compatibility - Update architecture-specific crash handling to use new APIs The multikernel case now properly uses list-based management instead of overwriting compatibility pointers, allowing multiple multikernel images to coexist in the system. Signed-off-by: Cong Wang --- arch/powerpc/kexec/crash.c | 8 ++-- arch/x86/kernel/crash.c | 4 +- include/linux/kexec.h | 13 ++++++ kernel/kexec.c | 60 ++++++++++++++++++++++++++-- kernel/kexec_core.c | 81 ++++++++++++++++++++++++++++++++++++++ kernel/kexec_file.c | 33 ++++++++++++++-- 6 files changed, 187 insertions(+), 12 deletions(-) diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c index a325c1c02f96..af190fad4f22 100644 --- a/arch/powerpc/kexec/crash.c +++ b/arch/powerpc/kexec/crash.c @@ -477,13 +477,13 @@ static void update_crash_elfcorehdr(struct kimage *im= age, struct memory_notify * ptr =3D __va(mem); if (ptr) { /* Temporarily invalidate the crash image while it is replaced */ - xchg(&kexec_crash_image, NULL); + kimage_update_compat_pointers(NULL, KEXEC_TYPE_CRASH); =20 /* Replace the old elfcorehdr with newly prepared elfcorehdr */ memcpy((void *)ptr, elfbuf, elfsz); =20 /* The crash image is now valid once again */ - xchg(&kexec_crash_image, image); + kimage_update_compat_pointers(image, KEXEC_TYPE_CRASH); } out: kvfree(cmem); @@ -537,14 +537,14 @@ static void update_crash_fdt(struct kimage *image) fdt =3D __va((void *)image->segment[fdt_index].mem); =20 /* Temporarily invalidate the crash image while it is replaced */ - xchg(&kexec_crash_image, NULL); + kimage_update_compat_pointers(NULL, KEXEC_TYPE_CRASH); =20 /* update FDT to reflect changes in CPU resources */ if (update_cpus_node(fdt)) pr_err("Failed to update crash FDT"); =20 /* The crash image is now valid once again */ - xchg(&kexec_crash_image, image); + kimage_update_compat_pointers(image, KEXEC_TYPE_CRASH); } =20 int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_f= lags) diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index 335fd2ee9766..a81f91d4352d 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -559,9 +559,9 @@ void arch_crash_handle_hotplug_event(struct kimage *ima= ge, void *arg) * Temporarily invalidate the crash image while the * elfcorehdr is updated. */ - xchg(&kexec_crash_image, NULL); + kimage_update_compat_pointers(NULL, KEXEC_TYPE_CRASH); memcpy_flushcache(old_elfcorehdr, elfbuf, elfsz); - xchg(&kexec_crash_image, image); + kimage_update_compat_pointers(image, KEXEC_TYPE_CRASH); kunmap_local(old_elfcorehdr); pr_debug("updated elfcorehdr\n"); =20 diff --git a/include/linux/kexec.h b/include/linux/kexec.h index edf64bc98ed5..69877db5360b 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -431,6 +431,9 @@ struct kimage { /* dm crypt keys buffer */ unsigned long dm_crypt_keys_addr; unsigned long dm_crypt_keys_sz; + + /* For multikernel support: linked list node */ + struct list_head list; }; =20 /* kexec interface functions */ @@ -534,6 +537,16 @@ extern bool kexec_file_dbg_print; =20 extern void *kimage_map_segment(struct kimage *image, unsigned long addr, = unsigned long size); extern void kimage_unmap_segment(void *buffer); + +/* Multikernel support functions */ +extern struct kimage *kimage_find_by_type(int type); +extern void kimage_add_to_list(struct kimage *image); +extern void kimage_remove_from_list(struct kimage *image); +extern void kimage_update_compat_pointers(struct kimage *new_image, int ty= pe); +extern int kimage_get_all_by_type(int type, struct kimage **images, int ma= x_count); +extern void kimage_list_lock(void); +extern void kimage_list_unlock(void); +extern void kimage_list_multikernel_images(void); #else /* !CONFIG_KEXEC_CORE */ struct pt_regs; struct task_struct; diff --git a/kernel/kexec.c b/kernel/kexec.c index 28008e3d462e..74b8df4670e0 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -114,7 +114,31 @@ static int do_kexec_load(unsigned long entry, unsigned= long nr_segments, =20 if (nr_segments =3D=3D 0) { /* Uninstall image */ - kimage_free(xchg(dest_image, NULL)); + if (flags & KEXEC_ON_CRASH) { + struct kimage *old_image =3D xchg(&kexec_crash_image, NULL); + if (old_image) { + kimage_remove_from_list(old_image); + kimage_free(old_image); + } + } else if (flags & KEXEC_MULTIKERNEL) { + /* For multikernel unload, we need to specify which image to remove */ + /* For now, remove all multikernel images - this could be enhanced */ + struct kimage *images[10]; + int count, i; + + count =3D kimage_get_all_by_type(KEXEC_TYPE_MULTIKERNEL, images, 10); + for (i =3D 0; i < count; i++) { + kimage_remove_from_list(images[i]); + kimage_free(images[i]); + } + pr_info("Unloaded %d multikernel images\n", count); + } else { + struct kimage *old_image =3D xchg(&kexec_image, NULL); + if (old_image) { + kimage_remove_from_list(old_image); + kimage_free(old_image); + } + } ret =3D 0; goto out_unlock; } @@ -124,7 +148,11 @@ static int do_kexec_load(unsigned long entry, unsigned= long nr_segments, * crashes. Free any current crash dump kernel before * we corrupt it. */ - kimage_free(xchg(&kexec_crash_image, NULL)); + struct kimage *old_crash_image =3D xchg(&kexec_crash_image, NULL); + if (old_crash_image) { + kimage_remove_from_list(old_crash_image); + kimage_free(old_crash_image); + } } =20 ret =3D kimage_alloc_init(&image, entry, nr_segments, segments, flags); @@ -164,7 +192,33 @@ static int do_kexec_load(unsigned long entry, unsigned= long nr_segments, goto out; =20 /* Install the new kernel and uninstall the old */ - image =3D xchg(dest_image, image); + if (flags & KEXEC_ON_CRASH) { + struct kimage *old_image =3D xchg(&kexec_crash_image, image); + if (old_image) { + kimage_remove_from_list(old_image); + kimage_free(old_image); + } + if (image) { + kimage_add_to_list(image); + kimage_update_compat_pointers(image, KEXEC_TYPE_CRASH); + } + image =3D NULL; /* Don't free the new image */ + } else if (flags & KEXEC_MULTIKERNEL) { + if (image) + kimage_add_to_list(image); + image =3D NULL; /* Don't free the new image */ + } else { + struct kimage *old_image =3D xchg(&kexec_image, image); + if (old_image) { + kimage_remove_from_list(old_image); + kimage_free(old_image); + } + if (image) { + kimage_add_to_list(image); + kimage_update_compat_pointers(image, KEXEC_TYPE_DEFAULT); + } + image =3D NULL; /* Don't free the new image */ + } =20 out: #ifdef CONFIG_CRASH_DUMP diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index 7d89d00e2cde..449096060fe8 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -56,6 +56,10 @@ bool kexec_in_progress =3D false; =20 bool kexec_file_dbg_print; =20 +/* Linked list of dynamically allocated kimages */ +static LIST_HEAD(kexec_image_list); +static DEFINE_MUTEX(kexec_image_mutex); + /* * When kexec transitions to the new kernel there is a one-to-one * mapping between physical and virtual addresses. On processors @@ -248,6 +252,9 @@ struct kimage *do_kimage_alloc_init(void) /* Initialize the list of unusable pages */ INIT_LIST_HEAD(&image->unusable_pages); =20 + /* Initialize the list node for multikernel support */ + INIT_LIST_HEAD(&image->list); + #ifdef CONFIG_CRASH_HOTPLUG image->hp_action =3D KEXEC_CRASH_HP_NONE; image->elfcorehdr_index =3D -1; @@ -580,6 +587,13 @@ void kimage_free(struct kimage *image) if (!image) return; =20 + /* Remove from linked list and update compatibility pointers */ + kimage_remove_from_list(image); + if (image =3D=3D kexec_image) + kimage_update_compat_pointers(NULL, KEXEC_TYPE_DEFAULT); + else if (image =3D=3D kexec_crash_image) + kimage_update_compat_pointers(NULL, KEXEC_TYPE_CRASH); + #ifdef CONFIG_CRASH_DUMP if (image->vmcoreinfo_data_copy) { crash_update_vmcoreinfo_safecopy(NULL); @@ -1096,6 +1110,72 @@ void kimage_unmap_segment(void *segment_buffer) vunmap(segment_buffer); } =20 +void kimage_add_to_list(struct kimage *image) +{ + mutex_lock(&kexec_image_mutex); + list_add_tail(&image->list, &kexec_image_list); + mutex_unlock(&kexec_image_mutex); +} + +void kimage_remove_from_list(struct kimage *image) +{ + mutex_lock(&kexec_image_mutex); + if (!list_empty(&image->list)) + list_del_init(&image->list); + mutex_unlock(&kexec_image_mutex); +} + +struct kimage *kimage_find_by_type(int type) +{ + struct kimage *image; + + mutex_lock(&kexec_image_mutex); + list_for_each_entry(image, &kexec_image_list, list) { + if (image->type =3D=3D type) { + mutex_unlock(&kexec_image_mutex); + return image; + } + } + mutex_unlock(&kexec_image_mutex); + return NULL; +} + +void kimage_update_compat_pointers(struct kimage *new_image, int type) +{ + mutex_lock(&kexec_image_mutex); + if (type =3D=3D KEXEC_TYPE_CRASH) { + kexec_crash_image =3D new_image; + } else if (type =3D=3D KEXEC_TYPE_DEFAULT) { + kexec_image =3D new_image; + } + mutex_unlock(&kexec_image_mutex); +} + +int kimage_get_all_by_type(int type, struct kimage **images, int max_count) +{ + struct kimage *image; + int count =3D 0; + + mutex_lock(&kexec_image_mutex); + list_for_each_entry(image, &kexec_image_list, list) { + if (image->type =3D=3D type && count < max_count) { + images[count++] =3D image; + } + } + mutex_unlock(&kexec_image_mutex); + return count; +} + +void kimage_list_lock(void) +{ + mutex_lock(&kexec_image_mutex); +} + +void kimage_list_unlock(void) +{ + mutex_unlock(&kexec_image_mutex); +} + struct kexec_load_limit { /* Mutex protects the limit count. */ struct mutex mutex; @@ -1112,6 +1192,7 @@ static struct kexec_load_limit load_limit_panic =3D { .limit =3D -1, }; =20 +/* Compatibility: maintain pointers to current default and crash images */ struct kimage *kexec_image; struct kimage *kexec_crash_image; static int kexec_load_disabled; diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index eb62a9794242..2d9d5626c8da 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -400,8 +400,13 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, = initrd_fd, * same memory where old crash kernel might be loaded. Free any * current crash dump kernel before we corrupt it. */ - if (flags & KEXEC_FILE_ON_CRASH) - kimage_free(xchg(&kexec_crash_image, NULL)); + if (flags & KEXEC_FILE_ON_CRASH) { + struct kimage *old_crash_image =3D xchg(&kexec_crash_image, NULL); + if (old_crash_image) { + kimage_remove_from_list(old_crash_image); + kimage_free(old_crash_image); + } + } =20 ret =3D kimage_file_alloc_init(&image, kernel_fd, initrd_fd, cmdline_ptr, cmdline_len, flags); @@ -457,7 +462,29 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, = initrd_fd, */ kimage_file_post_load_cleanup(image); exchange: - image =3D xchg(dest_image, image); + if (image_type =3D=3D KEXEC_TYPE_CRASH) { + struct kimage *old_image =3D xchg(&kexec_crash_image, image); + if (old_image) { + kimage_remove_from_list(old_image); + kimage_free(old_image); + } + if (image) { + kimage_add_to_list(image); + kimage_update_compat_pointers(image, KEXEC_TYPE_CRASH); + } + image =3D NULL; /* Don't free the new image */ + } else { + struct kimage *old_image =3D xchg(&kexec_image, image); + if (old_image) { + kimage_remove_from_list(old_image); + kimage_free(old_image); + } + if (image) { + kimage_add_to_list(image); + kimage_update_compat_pointers(image, KEXEC_TYPE_DEFAULT); + } + image =3D NULL; /* Don't free the new image */ + } out: #ifdef CONFIG_CRASH_DUMP if ((flags & KEXEC_FILE_ON_CRASH) && kexec_crash_image) --=20 2.34.1