| Message ID | 20220321080422.56255-5-sourabhjain@linux.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [RFC,v3,1/5] powerpc/kexec: make update_cpus_node non-static | expand |
Notes below. eric On 3/21/22 03:04, Sourabh Jain wrote: > Two major changes are done to enable the crash CPU hotplug handler. > Firstly, updated the kexec_load path to prepare kimage for hotplug > changes and secondly, implemented the crash hotplug handler itself. > > On the kexec load path, memsz allocation of crash FDT segment is > updated to ensure that it has sufficient buffer space to accommodate > future hot add CPUs. Initialized the kimage members to track the FDT > segment. > > The crash hotplug handler updates the cpus node of crash FDT. While > we update crash FDT the kexec_crash_image is marked invalid and restored > after FDT update to avoid race. > > Since memory crash hotplug support is not there yet the crash hotplug > handler simply warn the user and return. > > Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com> > --- > arch/powerpc/kexec/core_64.c | 46 ++++++++++++++++++++++++++++++++++++ > arch/powerpc/kexec/elf_64.c | 40 +++++++++++++++++++++++++++++++ > 2 files changed, 86 insertions(+) > > diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c > index 249d2632526d..a470fe6904e3 100644 > --- a/arch/powerpc/kexec/core_64.c > +++ b/arch/powerpc/kexec/core_64.c > @@ -466,6 +466,52 @@ int update_cpus_node(void *fdt) > return ret; > } > > +#ifdef CONFIG_CRASH_HOTPLUG > +/** > + * arch_crash_hotplug_handler() - Handle hotplug FDT changes > + * @image: the active struct kimage > + * @hp_action: the hot un/plug action being handled > + * @a: first parameter dependent upon hp_action > + * @b: first parameter dependent upon hp_action > + * > + * To accurately reflect CPU hot un/plug changes, the FDT > + * must be updated with the new list of CPUs and memories. > + */ > +void arch_crash_hotplug_handler(struct kimage *image, unsigned int hp_action, > + unsigned long a, unsigned long b) > +{ > + void *fdt; > + > + /* No action needed for CPU hot-unplug */ > + if (hp_action == KEXEC_CRASH_HP_REMOVE_CPU) > + return; Just curious why no action is needed on cpu remove? > + > + /* crash update on memory hotplug is not support yet */ > + if (hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY || hp_action == KEXEC_CRASH_HP_ADD_MEMORY) { > + pr_err("crash hp: crash update is not supported with memory hotplug\n"); > + return; > + } > + > + /* Must have valid FDT index */ > + if (!image->arch.fdt_index_valid) { > + pr_err("crash hp: unable to locate FDT segment"); > + return; > + } > + > + fdt = __va((void *)image->segment[image->arch.fdt_index].mem); > + > + /* Temporarily invalidate the crash image while it is replaced */ > + xchg(&kexec_crash_image, NULL); > + > + /* update FDT to refelect changes to CPU resrouces */ > + if (update_cpus_node(fdt)) > + pr_err("crash hp: failed to update crash FDT"); > + > + /* The crash image is now valid once again */ > + xchg(&kexec_crash_image, image); > +} > +#endif /* CONFIG_CRASH_HOTPLUG */ > + > #ifdef CONFIG_PPC_64S_HASH_MMU > /* Values we need to export to the second kernel via the device tree. */ > static unsigned long htab_base; > diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c > index eeb258002d1e..2ffe6d69e186 100644 > --- a/arch/powerpc/kexec/elf_64.c > +++ b/arch/powerpc/kexec/elf_64.c > @@ -24,6 +24,33 @@ > #include <linux/slab.h> > #include <linux/types.h> > > + > +#ifdef CONFIG_CRASH_HOTPLUG > +#define MAX_CORE 256 Is there a better config option to tie this value too? > +#define PER_CORE_NODE_SIZE 1500 > + > +/** > + * get_crash_fdt_mem_sz() - calcuate mem size for crash kernel FDT > + * @fdt: pointer to crash kernel FDT > + * > + * Calculate the buffer space needed to add more CPU nodes in FDT after > + * capture kenrel load due to hot add events. > + * > + * Some assumption are made to calculate the additional buffer size needed > + * to accommodate future hot add CPUs to the crash FDT. The maximum core count > + * in the system would not go beyond MAX_CORE and memory needed to store per core > + * date in FDT is PER_CORE_NODE_SIZE. > + * > + * Certainly MAX_CORE count can be replaced with possible core count and > + * PER_CORE_NODE_SIZE to some standard value instead of randomly observed > + * core size value on Power9 LPAR. > + */ > +static unsigned int get_crash_fdt_mem_sz(void *fdt) > +{ > + return fdt_totalsize(fdt) + (PER_CORE_NODE_SIZE * MAX_CORE); > +} > +#endif > + > static void *elf64_load(struct kimage *image, char *kernel_buf, > unsigned long kernel_len, char *initrd, > unsigned long initrd_len, char *cmdline, > @@ -123,6 +150,19 @@ static void *elf64_load(struct kimage *image, char *kernel_buf, > kbuf.buf_align = PAGE_SIZE; > kbuf.top_down = true; > kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; > + > +#ifdef CONFIG_CRASH_HOTPLUG > + if (image->type == KEXEC_TYPE_CRASH) { > + kbuf.memsz = get_crash_fdt_mem_sz(fdt); > + fdt_set_totalsize(fdt, kbuf.memsz); > + image->arch.fdt_index = image->nr_segments; > + image->arch.fdt_index_valid = true; > + } else > +#endif > + { > + kbuf.memsz = fdt_totalsize(fdt); > + } > + > ret = kexec_add_buffer(&kbuf); > if (ret) > goto out_free_fdt; >
Hello Eric, On 24/03/22 00:02, Eric DeVolder wrote: > Notes below. > eric > > On 3/21/22 03:04, Sourabh Jain wrote: >> Two major changes are done to enable the crash CPU hotplug handler. >> Firstly, updated the kexec_load path to prepare kimage for hotplug >> changes and secondly, implemented the crash hotplug handler itself. >> >> On the kexec load path, memsz allocation of crash FDT segment is >> updated to ensure that it has sufficient buffer space to accommodate >> future hot add CPUs. Initialized the kimage members to track the FDT >> segment. >> >> The crash hotplug handler updates the cpus node of crash FDT. While >> we update crash FDT the kexec_crash_image is marked invalid and restored >> after FDT update to avoid race. >> >> Since memory crash hotplug support is not there yet the crash hotplug >> handler simply warn the user and return. >> >> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com> >> --- >> arch/powerpc/kexec/core_64.c | 46 ++++++++++++++++++++++++++++++++++++ >> arch/powerpc/kexec/elf_64.c | 40 +++++++++++++++++++++++++++++++ >> 2 files changed, 86 insertions(+) >> >> diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c >> index 249d2632526d..a470fe6904e3 100644 >> --- a/arch/powerpc/kexec/core_64.c >> +++ b/arch/powerpc/kexec/core_64.c >> @@ -466,6 +466,52 @@ int update_cpus_node(void *fdt) >> return ret; >> } >> +#ifdef CONFIG_CRASH_HOTPLUG >> +/** >> + * arch_crash_hotplug_handler() - Handle hotplug FDT changes >> + * @image: the active struct kimage >> + * @hp_action: the hot un/plug action being handled >> + * @a: first parameter dependent upon hp_action >> + * @b: first parameter dependent upon hp_action >> + * >> + * To accurately reflect CPU hot un/plug changes, the FDT >> + * must be updated with the new list of CPUs and memories. >> + */ >> +void arch_crash_hotplug_handler(struct kimage *image, unsigned int >> hp_action, >> + unsigned long a, unsigned long b) >> +{ >> + void *fdt; >> + >> + /* No action needed for CPU hot-unplug */ >> + if (hp_action == KEXEC_CRASH_HP_REMOVE_CPU) >> + return; > Just curious why no action is needed on cpu remove? Since CPU note addresses are already available for all possible CPUs (regardless they are online or not) the PHDR is allocated for all possible CPUs during elfcorehdr creation. At least for the kexec_load system call. Now on the crash path, the crashing CPU initiates an IPI call to update the CPU data of all online CPUs and jumps to the purgatory. Hence no action is needed for the remove case. With the above logic, we shouldn't be taking any action for the CPU add case too, right? But on PowerPC early boot path there is validation that checks the boot CPU is part of the Flattened Device Tree (FDT) or not. If the boot CPU is not found in FDT the boot fails. Hence FDT needs to be updated for every new CPU added to the system. > >> + >> + /* crash update on memory hotplug is not support yet */ >> + if (hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY || hp_action == >> KEXEC_CRASH_HP_ADD_MEMORY) { >> + pr_err("crash hp: crash update is not supported with memory >> hotplug\n"); >> + return; >> + } >> + >> + /* Must have valid FDT index */ >> + if (!image->arch.fdt_index_valid) { >> + pr_err("crash hp: unable to locate FDT segment"); >> + return; >> + } >> + >> + fdt = __va((void *)image->segment[image->arch.fdt_index].mem); >> + >> + /* Temporarily invalidate the crash image while it is replaced */ >> + xchg(&kexec_crash_image, NULL); >> + >> + /* update FDT to refelect changes to CPU resrouces */ >> + if (update_cpus_node(fdt)) >> + pr_err("crash hp: failed to update crash FDT"); >> + >> + /* The crash image is now valid once again */ >> + xchg(&kexec_crash_image, image); >> +} >> +#endif /* CONFIG_CRASH_HOTPLUG */ >> + >> #ifdef CONFIG_PPC_64S_HASH_MMU >> /* Values we need to export to the second kernel via the device >> tree. */ >> static unsigned long htab_base; >> diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c >> index eeb258002d1e..2ffe6d69e186 100644 >> --- a/arch/powerpc/kexec/elf_64.c >> +++ b/arch/powerpc/kexec/elf_64.c >> @@ -24,6 +24,33 @@ >> #include <linux/slab.h> >> #include <linux/types.h> >> + >> +#ifdef CONFIG_CRASH_HOTPLUG >> +#define MAX_CORE 256 > Is there a better config option to tie this value too? The above #defines are just placeholders. Eventually, we will replace the MAX_CORE with possible CPUs to calculate the FDT size. Maybe in the next version, the above #define will be removed. >> +#define PER_CORE_NODE_SIZE 1500 >> + >> Thanks for the review Eric. - Sourabh Jain
On 21/03/2022, 09:04:21, Sourabh Jain wrote: > Two major changes are done to enable the crash CPU hotplug handler. > Firstly, updated the kexec_load path to prepare kimage for hotplug > changes and secondly, implemented the crash hotplug handler itself. > > On the kexec load path, memsz allocation of crash FDT segment is > updated to ensure that it has sufficient buffer space to accommodate > future hot add CPUs. Initialized the kimage members to track the FDT > segment. > > The crash hotplug handler updates the cpus node of crash FDT. While > we update crash FDT the kexec_crash_image is marked invalid and restored > after FDT update to avoid race. > > Since memory crash hotplug support is not there yet the crash hotplug > handler simply warn the user and return. > > Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com> > --- > arch/powerpc/kexec/core_64.c | 46 ++++++++++++++++++++++++++++++++++++ > arch/powerpc/kexec/elf_64.c | 40 +++++++++++++++++++++++++++++++ > 2 files changed, 86 insertions(+) > > diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c > index 249d2632526d..a470fe6904e3 100644 > --- a/arch/powerpc/kexec/core_64.c > +++ b/arch/powerpc/kexec/core_64.c > @@ -466,6 +466,52 @@ int update_cpus_node(void *fdt) > return ret; > } > > +#ifdef CONFIG_CRASH_HOTPLUG > +/** > + * arch_crash_hotplug_handler() - Handle hotplug FDT changes > + * @image: the active struct kimage > + * @hp_action: the hot un/plug action being handled > + * @a: first parameter dependent upon hp_action > + * @b: first parameter dependent upon hp_action > + * > + * To accurately reflect CPU hot un/plug changes, the FDT > + * must be updated with the new list of CPUs and memories. > + */ > +void arch_crash_hotplug_handler(struct kimage *image, unsigned int hp_action, > + unsigned long a, unsigned long b) > +{ > + void *fdt; > + > + /* No action needed for CPU hot-unplug */ > + if (hp_action == KEXEC_CRASH_HP_REMOVE_CPU) > + return; > + > + /* crash update on memory hotplug is not support yet */ > + if (hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY || hp_action == KEXEC_CRASH_HP_ADD_MEMORY) { > + pr_err("crash hp: crash update is not supported with memory hotplug\n"); May be pr_info_once() that's not really an error ? > + return; > + } > + > + /* Must have valid FDT index */ > + if (!image->arch.fdt_index_valid) { > + pr_err("crash hp: unable to locate FDT segment"); > + return; > + } > + > + fdt = __va((void *)image->segment[image->arch.fdt_index].mem); > + > + /* Temporarily invalidate the crash image while it is replaced */ > + xchg(&kexec_crash_image, NULL); > + > + /* update FDT to refelect changes to CPU resrouces */ > + if (update_cpus_node(fdt)) > + pr_err("crash hp: failed to update crash FDT"); > + > + /* The crash image is now valid once again */ > + xchg(&kexec_crash_image, image); > +} > +#endif /* CONFIG_CRASH_HOTPLUG */ > + > #ifdef CONFIG_PPC_64S_HASH_MMU > /* Values we need to export to the second kernel via the device tree. */ > static unsigned long htab_base; > diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c > index eeb258002d1e..2ffe6d69e186 100644 > --- a/arch/powerpc/kexec/elf_64.c > +++ b/arch/powerpc/kexec/elf_64.c > @@ -24,6 +24,33 @@ > #include <linux/slab.h> > #include <linux/types.h> > > + > +#ifdef CONFIG_CRASH_HOTPLUG > +#define MAX_CORE 256 Why not computing something based on nr_cpus_ids and threads_per_core instead? > +#define PER_CORE_NODE_SIZE 1500 Is that size function of threadsd_per_core too? > +> +/** > + * get_crash_fdt_mem_sz() - calcuate mem size for crash kernel FDT > + * @fdt: pointer to crash kernel FDT > + * > + * Calculate the buffer space needed to add more CPU nodes in FDT after > + * capture kenrel load due to hot add events. kernel > + * > + * Some assumption are made to calculate the additional buffer size needed > + * to accommodate future hot add CPUs to the crash FDT. The maximum core count > + * in the system would not go beyond MAX_CORE and memory needed to store per core > + * date in FDT is PER_CORE_NODE_SIZE. > + * > + * Certainly MAX_CORE count can be replaced with possible core count and > + * PER_CORE_NODE_SIZE to some standard value instead of randomly observed > + * core size value on Power9 LPAR. See above. > + */ > +static unsigned int get_crash_fdt_mem_sz(void *fdt) > +{ > + return fdt_totalsize(fdt) + (PER_CORE_NODE_SIZE * MAX_CORE); I guess fdt_totalsize() is already taken in account the online CPUs, isn't it? If that's the case, you should add the remaining needed part only. > +} > +#endif > + > static void *elf64_load(struct kimage *image, char *kernel_buf, > unsigned long kernel_len, char *initrd, > unsigned long initrd_len, char *cmdline, > @@ -123,6 +150,19 @@ static void *elf64_load(struct kimage *image, char *kernel_buf, > kbuf.buf_align = PAGE_SIZE; > kbuf.top_down = true; > kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; > + > +#ifdef CONFIG_CRASH_HOTPLUG > + if (image->type == KEXEC_TYPE_CRASH) { > + kbuf.memsz = get_crash_fdt_mem_sz(fdt); > + fdt_set_totalsize(fdt, kbuf.memsz); > + image->arch.fdt_index = image->nr_segments; > + image->arch.fdt_index_valid = true; > + } else > +#endif > + { > + kbuf.memsz = fdt_totalsize(fdt); > + } > + > ret = kexec_add_buffer(&kbuf); > if (ret) > goto out_free_fdt;
Hi Laurent, On 25/03/22 23:33, Laurent Dufour wrote: > On 21/03/2022, 09:04:21, Sourabh Jain wrote: >> Two major changes are done to enable the crash CPU hotplug handler. >> Firstly, updated the kexec_load path to prepare kimage for hotplug >> changes and secondly, implemented the crash hotplug handler itself. >> >> On the kexec load path, memsz allocation of crash FDT segment is >> updated to ensure that it has sufficient buffer space to accommodate >> future hot add CPUs. Initialized the kimage members to track the FDT >> segment. >> >> The crash hotplug handler updates the cpus node of crash FDT. While >> we update crash FDT the kexec_crash_image is marked invalid and restored >> after FDT update to avoid race. >> >> Since memory crash hotplug support is not there yet the crash hotplug >> handler simply warn the user and return. >> >> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com> >> --- >> arch/powerpc/kexec/core_64.c | 46 ++++++++++++++++++++++++++++++++++++ >> arch/powerpc/kexec/elf_64.c | 40 +++++++++++++++++++++++++++++++ >> 2 files changed, 86 insertions(+) >> >> diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c >> index 249d2632526d..a470fe6904e3 100644 >> --- a/arch/powerpc/kexec/core_64.c >> +++ b/arch/powerpc/kexec/core_64.c >> @@ -466,6 +466,52 @@ int update_cpus_node(void *fdt) >> return ret; >> } >> >> +#ifdef CONFIG_CRASH_HOTPLUG >> +/** >> + * arch_crash_hotplug_handler() - Handle hotplug FDT changes >> + * @image: the active struct kimage >> + * @hp_action: the hot un/plug action being handled >> + * @a: first parameter dependent upon hp_action >> + * @b: first parameter dependent upon hp_action >> + * >> + * To accurately reflect CPU hot un/plug changes, the FDT >> + * must be updated with the new list of CPUs and memories. >> + */ >> +void arch_crash_hotplug_handler(struct kimage *image, unsigned int hp_action, >> + unsigned long a, unsigned long b) >> +{ >> + void *fdt; >> + >> + /* No action needed for CPU hot-unplug */ >> + if (hp_action == KEXEC_CRASH_HP_REMOVE_CPU) >> + return; >> + >> + /* crash update on memory hotplug is not support yet */ >> + if (hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY || hp_action == KEXEC_CRASH_HP_ADD_MEMORY) { >> + pr_err("crash hp: crash update is not supported with memory hotplug\n"); > > May be pr_info_once() that's not really an error ? Ye not an error. > >> + return; >> + } >> + >> + /* Must have valid FDT index */ >> + if (!image->arch.fdt_index_valid) { >> + pr_err("crash hp: unable to locate FDT segment"); >> + return; >> + } >> + >> + fdt = __va((void *)image->segment[image->arch.fdt_index].mem); >> + >> + /* Temporarily invalidate the crash image while it is replaced */ >> + xchg(&kexec_crash_image, NULL); >> + >> + /* update FDT to refelect changes to CPU resrouces */ >> + if (update_cpus_node(fdt)) >> + pr_err("crash hp: failed to update crash FDT"); >> + >> + /* The crash image is now valid once again */ >> + xchg(&kexec_crash_image, image); >> +} >> +#endif /* CONFIG_CRASH_HOTPLUG */ >> + >> #ifdef CONFIG_PPC_64S_HASH_MMU >> /* Values we need to export to the second kernel via the device tree. */ >> static unsigned long htab_base; >> diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c >> index eeb258002d1e..2ffe6d69e186 100644 >> --- a/arch/powerpc/kexec/elf_64.c >> +++ b/arch/powerpc/kexec/elf_64.c >> @@ -24,6 +24,33 @@ >> #include <linux/slab.h> >> #include <linux/types.h> >> >> + >> +#ifdef CONFIG_CRASH_HOTPLUG >> +#define MAX_CORE 256 > Why not computing something based on nr_cpus_ids and threads_per_core instead? Yes in the next version I will change this to nr_cpus. > >> +#define PER_CORE_NODE_SIZE 1500 > Is that size function of threadsd_per_core too? It is per core basis. I noticed that the size of FDT get increased by approx 1.5 KB after adding a core. In next version this patch series, we will be computing FDT buffer size needed of hotplug CPUs based on the existing core size. While loading the kdump kernel we will go through all attributes of the currently online CPU and use them to calculate the buffer space needed for hotplug CPUs. >> + * >> + * Some assumption are made to calculate the additional buffer size needed >> + * to accommodate future hot add CPUs to the crash FDT. The maximum core count >> + * in the system would not go beyond MAX_CORE and memory needed to store per core >> + * date in FDT is PER_CORE_NODE_SIZE. >> + * >> + * Certainly MAX_CORE count can be replaced with possible core count and >> + * PER_CORE_NODE_SIZE to some standard value instead of randomly observed >> + * core size value on Power9 LPAR. > See above. > >> + */ >> +static unsigned int get_crash_fdt_mem_sz(void *fdt) >> +{ >> + return fdt_totalsize(fdt) + (PER_CORE_NODE_SIZE * MAX_CORE); > I guess fdt_totalsize() is already taken in account the online CPUs, isn't it? > If that's the case, you should add the remaining needed part only. Agree, I will take of that in next series. Thanks for the review. - Sourabh Jain
diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c index 249d2632526d..a470fe6904e3 100644 --- a/arch/powerpc/kexec/core_64.c +++ b/arch/powerpc/kexec/core_64.c @@ -466,6 +466,52 @@ int update_cpus_node(void *fdt) return ret; } +#ifdef CONFIG_CRASH_HOTPLUG +/** + * arch_crash_hotplug_handler() - Handle hotplug FDT changes + * @image: the active struct kimage + * @hp_action: the hot un/plug action being handled + * @a: first parameter dependent upon hp_action + * @b: first parameter dependent upon hp_action + * + * To accurately reflect CPU hot un/plug changes, the FDT + * must be updated with the new list of CPUs and memories. + */ +void arch_crash_hotplug_handler(struct kimage *image, unsigned int hp_action, + unsigned long a, unsigned long b) +{ + void *fdt; + + /* No action needed for CPU hot-unplug */ + if (hp_action == KEXEC_CRASH_HP_REMOVE_CPU) + return; + + /* crash update on memory hotplug is not support yet */ + if (hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY || hp_action == KEXEC_CRASH_HP_ADD_MEMORY) { + pr_err("crash hp: crash update is not supported with memory hotplug\n"); + return; + } + + /* Must have valid FDT index */ + if (!image->arch.fdt_index_valid) { + pr_err("crash hp: unable to locate FDT segment"); + return; + } + + fdt = __va((void *)image->segment[image->arch.fdt_index].mem); + + /* Temporarily invalidate the crash image while it is replaced */ + xchg(&kexec_crash_image, NULL); + + /* update FDT to refelect changes to CPU resrouces */ + if (update_cpus_node(fdt)) + pr_err("crash hp: failed to update crash FDT"); + + /* The crash image is now valid once again */ + xchg(&kexec_crash_image, image); +} +#endif /* CONFIG_CRASH_HOTPLUG */ + #ifdef CONFIG_PPC_64S_HASH_MMU /* Values we need to export to the second kernel via the device tree. */ static unsigned long htab_base; diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c index eeb258002d1e..2ffe6d69e186 100644 --- a/arch/powerpc/kexec/elf_64.c +++ b/arch/powerpc/kexec/elf_64.c @@ -24,6 +24,33 @@ #include <linux/slab.h> #include <linux/types.h> + +#ifdef CONFIG_CRASH_HOTPLUG +#define MAX_CORE 256 +#define PER_CORE_NODE_SIZE 1500 + +/** + * get_crash_fdt_mem_sz() - calcuate mem size for crash kernel FDT + * @fdt: pointer to crash kernel FDT + * + * Calculate the buffer space needed to add more CPU nodes in FDT after + * capture kenrel load due to hot add events. + * + * Some assumption are made to calculate the additional buffer size needed + * to accommodate future hot add CPUs to the crash FDT. The maximum core count + * in the system would not go beyond MAX_CORE and memory needed to store per core + * date in FDT is PER_CORE_NODE_SIZE. + * + * Certainly MAX_CORE count can be replaced with possible core count and + * PER_CORE_NODE_SIZE to some standard value instead of randomly observed + * core size value on Power9 LPAR. + */ +static unsigned int get_crash_fdt_mem_sz(void *fdt) +{ + return fdt_totalsize(fdt) + (PER_CORE_NODE_SIZE * MAX_CORE); +} +#endif + static void *elf64_load(struct kimage *image, char *kernel_buf, unsigned long kernel_len, char *initrd, unsigned long initrd_len, char *cmdline, @@ -123,6 +150,19 @@ static void *elf64_load(struct kimage *image, char *kernel_buf, kbuf.buf_align = PAGE_SIZE; kbuf.top_down = true; kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; + +#ifdef CONFIG_CRASH_HOTPLUG + if (image->type == KEXEC_TYPE_CRASH) { + kbuf.memsz = get_crash_fdt_mem_sz(fdt); + fdt_set_totalsize(fdt, kbuf.memsz); + image->arch.fdt_index = image->nr_segments; + image->arch.fdt_index_valid = true; + } else +#endif + { + kbuf.memsz = fdt_totalsize(fdt); + } + ret = kexec_add_buffer(&kbuf); if (ret) goto out_free_fdt;
Two major changes are done to enable the crash CPU hotplug handler. Firstly, updated the kexec_load path to prepare kimage for hotplug changes and secondly, implemented the crash hotplug handler itself. On the kexec load path, memsz allocation of crash FDT segment is updated to ensure that it has sufficient buffer space to accommodate future hot add CPUs. Initialized the kimage members to track the FDT segment. The crash hotplug handler updates the cpus node of crash FDT. While we update crash FDT the kexec_crash_image is marked invalid and restored after FDT update to avoid race. Since memory crash hotplug support is not there yet the crash hotplug handler simply warn the user and return. Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com> --- arch/powerpc/kexec/core_64.c | 46 ++++++++++++++++++++++++++++++++++++ arch/powerpc/kexec/elf_64.c | 40 +++++++++++++++++++++++++++++++ 2 files changed, 86 insertions(+)