On 15/03/22 19:42, Eric DeVolder wrote:
On 3/15/22 07:08, Sourabh Jain wrote:
Hello Eric,
On 03/03/22 21:57, Eric DeVolder wrote:
This patch introduces a generic crash hot plug/unplug infrastructure
for CPU and memory changes. Upon CPU and memory changes, a generic
crash_hotplug_handler() obtains the appropriate lock, does some
important house keeping and then dispatches the hot plug/unplug event
to the architecture specific arch_crash_hotplug_handler(), and when
that handler returns, the lock is released.
This patch modifies crash_core.c to implement a subsys_initcall()
function that installs handlers for hot plug/unplug events. If CPU
hotplug is enabled, then cpuhp_setup_state() is invoked to register a
handler for CPU changes. Similarly, if memory hotplug is enabled, then
register_memory_notifier() is invoked to install a handler for memory
changes. These handlers in turn invoke the common generic handler
crash_hotplug_handler().
On the CPU side, cpuhp_setup_state_nocalls() is invoked with parameter
CPUHP_AP_ONLINE_DYN. While this works, when a CPU is being unplugged,
the CPU still shows up in foreach_present_cpu() during the regeneration
of the new CPU list, thus the need to explicitly check and exclude the
soon-to-be offlined CPU in crash_prepare_elf64_headers().
On the memory side, each un/plugged memory block passes through the
handler. For example, if a 1GiB DIMM is hotplugged, that generate 8
memory events, one for each 128MiB memblock.
Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx>
---
include/linux/kexec.h | 16 +++++++
kernel/crash_core.c | 108
++++++++++++++++++++++++++++++++++++++++++
2 files changed, 124 insertions(+)
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index d7b59248441b..b11d75a6b2bc 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -300,6 +300,13 @@ struct kimage {
/* Information for loading purgatory */
struct purgatory_info purgatory_info;
+
+#ifdef CONFIG_CRASH_HOTPLUG
+ bool hotplug_event;
+ int offlinecpu;
+ bool elf_index_valid;
+ int elf_index;
How about keeping an array to track all kexec segment index need to
be updated in
crash hotplug handler.
struct hp_segment {
name;
index;
is_valid;
}
It will be helpful if architecture need to updated multiple kexec
segments for a hotplug event.
For example, on PowerPC, we might need to update FDT and elfcorehdr
on memory hot plug/unplug.
Thanks,
Sourabh Jain
Sourabh,
I'm OK with that. Another idea might be if there are just two, and one
of them is elfcorehdr, then perhaps in addition to elf_index and
elf_index_valid, maybe we add an arch_index and arch_index_valid? In
the case of PPC, the FDT would be stored in arch_index?
Yes it seems like we might not need to keep more than two kexec indexes.
Since this indexes are arch specific lets push them to struct
kimage_arch (part of kimage). So for now I will push fdt_index to struct
kimage_arch.
Thanks,
Sourabh Jain
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