| 932bed41 | 10-May-2024 |
Sourabh Jain <[email protected]> |
powerpc/kexec_file: fix cpus node update to FDT
While updating the cpus node, commit 40c753993e3a ("powerpc/kexec_file:
Use current CPU info while setting up FDT") first deletes all subnodes
under
powerpc/kexec_file: fix cpus node update to FDT
While updating the cpus node, commit 40c753993e3a ("powerpc/kexec_file:
Use current CPU info while setting up FDT") first deletes all subnodes
under the /cpus node. However, while adding sub-nodes back, it missed
adding cpus subnodes whose device_type != "cpu", such as l2-cache*,
l3-cache*, ibm,powerpc-cpu-features.
Fix this by only deleting cpus sub-nodes of device_type == "cpus" and
then adding all available nodes with device_type == "cpu".
Fixes: 40c753993e3a ("powerpc/kexec_file: Use current CPU info while setting up FDT")
Signed-off-by: Sourabh Jain <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://msgid.link/[email protected]
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| 849599b7 | 26-Mar-2024 |
Sourabh Jain <[email protected]> |
powerpc/crash: add crash memory hotplug support
Extend the arch crash hotplug handler, as introduced by the patch title
("powerpc: add crash CPU hotplug support"), to also support memory
add/remove
powerpc/crash: add crash memory hotplug support
Extend the arch crash hotplug handler, as introduced by the patch title
("powerpc: add crash CPU hotplug support"), to also support memory
add/remove events.
Elfcorehdr describes the memory of the crash kernel to capture the
kernel; hence, it needs to be updated if memory resources change due to
memory add/remove events. Therefore, arch_crash_handle_hotplug_event()
is updated to recreate the elfcorehdr and replace it with the previous
one on memory add/remove events.
The memblock list is used to prepare the elfcorehdr. In the case of
memory hot remove, the memblock list is updated after the arch crash
hotplug handler is triggered, as depicted in Figure 1. Thus, the
hot-removed memory is explicitly removed from the crash memory ranges
to ensure that the memory ranges added to elfcorehdr do not include the
hot-removed memory.
Memory remove
|
v
Offline pages
|
v
Initiate memory notify call <----> crash hotplug handler
chain for MEM_OFFLINE event
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v
Update memblock list
Figure 1
There are two system calls, `kexec_file_load` and `kexec_load`, used to
load the kdump image. A few changes have been made to ensure that the
kernel can safely update the elfcorehdr component of the kdump image for
both system calls.
For the kexec_file_load syscall, kdump image is prepared in the kernel.
To support an increasing number of memory regions, the elfcorehdr is
built with extra buffer space to ensure that it can accommodate
additional memory ranges in future.
For the kexec_load syscall, the elfcorehdr is updated only if the
KEXEC_CRASH_HOTPLUG_SUPPORT kexec flag is passed to the kernel by the
kexec tool. Passing this flag to the kernel indicates that the
elfcorehdr is built to accommodate additional memory ranges and the
elfcorehdr segment is not considered for SHA calculation, making it safe
to update.
The changes related to this feature are kept under the CRASH_HOTPLUG
config, and it is enabled by default.
Signed-off-by: Sourabh Jain <[email protected]>
Acked-by: Hari Bathini <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://msgid.link/[email protected]
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| b741092d | 26-Mar-2024 |
Sourabh Jain <[email protected]> |
powerpc/crash: add crash CPU hotplug support
Due to CPU/Memory hotplug or online/offline events, the elfcorehdr
(which describes the CPUs and memory of the crashed kernel) and FDT
(Flattened Device
powerpc/crash: add crash CPU hotplug support
Due to CPU/Memory hotplug or online/offline events, the elfcorehdr
(which describes the CPUs and memory of the crashed kernel) and FDT
(Flattened Device Tree) of kdump image becomes outdated. Consequently,
attempting dump collection with an outdated elfcorehdr or FDT can lead
to failed or inaccurate dump collection.
Going forward, CPU hotplug or online/offline events are referred as
CPU/Memory add/remove events.
The current solution to address the above issue involves monitoring the
CPU/Memory add/remove events in userspace using udev rules and whenever
there are changes in CPU and memory resources, the entire kdump image
is loaded again. The kdump image includes kernel, initrd, elfcorehdr,
FDT, purgatory. Given that only elfcorehdr and FDT get outdated due to
CPU/Memory add/remove events, reloading the entire kdump image is
inefficient. More importantly, kdump remains inactive for a substantial
amount of time until the kdump reload completes.
To address the aforementioned issue, commit 247262756121 ("crash: add
generic infrastructure for crash hotplug support") added a generic
infrastructure that allows architectures to selectively update the kdump
image component during CPU or memory add/remove events within the kernel
itself.
In the event of a CPU or memory add/remove events, the generic crash
hotplug event handler, `crash_handle_hotplug_event()`, is triggered. It
then acquires the necessary locks to update the kdump image and invokes
the architecture-specific crash hotplug handler,
`arch_crash_handle_hotplug_event()`, to update the required kdump image
components.
This patch adds crash hotplug handler for PowerPC and enable support to
update the kdump image on CPU add/remove events. Support for memory
add/remove events is added in a subsequent patch with the title
"powerpc: add crash memory hotplug support"
As mentioned earlier, only the elfcorehdr and FDT kdump image components
need to be updated in the event of CPU or memory add/remove events.
However, on PowerPC architecture crash hotplug handler only updates the
FDT to enable crash hotplug support for CPU add/remove events. Here's
why.
The elfcorehdr on PowerPC is built with possible CPUs, and thus, it does
not need an update on CPU add/remove events. On the other hand, the FDT
needs to be updated on CPU add events to include the newly added CPU. If
the FDT is not updated and the kernel crashes on a newly added CPU, the
kdump kernel will fail to boot due to the unavailability of the crashing
CPU in the FDT. During the early boot, it is expected that the boot CPU
must be a part of the FDT; otherwise, the kernel will raise a BUG and
fail to boot. For more information, refer to commit 36ae37e3436b0
("powerpc: Make boot_cpuid common between 32 and 64-bit"). Since it is
okay to have an offline CPU in the kdump FDT, no action is taken in case
of CPU removal.
There are two system calls, `kexec_file_load` and `kexec_load`, used to
load the kdump image. Few changes have been made to ensure kernel can
safely update the FDT of kdump image loaded using both system calls.
For kexec_file_load syscall the kdump image is prepared in kernel. So to
support an increasing number of CPUs, the FDT is constructed with extra
buffer space to ensure it can accommodate a possible number of CPU
nodes. Additionally, a call to fdt_pack (which trims the unused space
once the FDT is prepared) is avoided if this feature is enabled.
For the kexec_load syscall, the FDT is updated only if the
KEXEC_CRASH_HOTPLUG_SUPPORT kexec flag is passed to the kernel by
userspace (kexec tools). When userspace passes this flag to the kernel,
it indicates that the FDT is built to accommodate possible CPUs, and the
FDT segment is excluded from SHA calculation, making it safe to update.
The changes related to this feature are kept under the CRASH_HOTPLUG
config, and it is enabled by default.
Signed-off-by: Sourabh Jain <[email protected]>
Acked-by: Hari Bathini <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://msgid.link/[email protected]
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| 36e826b5 | 23-Oct-2023 |
Aditya Gupta <[email protected]> |
powerpc/vmcore: Add MMU information to vmcoreinfo
Since below commit, address mapping for vmemmap has changed for Radix
MMU, where address mapping is stored in kernel page table itself,
instead of e
powerpc/vmcore: Add MMU information to vmcoreinfo
Since below commit, address mapping for vmemmap has changed for Radix
MMU, where address mapping is stored in kernel page table itself,
instead of earlier used 'vmemmap_list'.
commit 368a0590d954 ("powerpc/book3s64/vmemmap: switch radix to use
a different vmemmap handling function")
Hence with upstream kernel, in case of Radix MMU, makedumpfile fails
to do address translation for vmemmap addresses, as it depended on
vmemmap_list, which can now be empty.
While fixing the address translation in makedumpfile, it was identified
that currently makedumpfile cannot distinguish between Hash MMU and
Radix MMU, unless VMLINUX is passed with -x flag to makedumpfile. And
hence fails to assign offsets and shifts correctly (such as in L4 to
PGDIR offset calculation in makedumpfile).
For getting the MMU, makedumpfile uses `cur_cpu_spec.mmu_features`.
Add `cur_cpu_spec` symbol and offset of `mmu_features` in the `cpu_spec`
struct, to VMCOREINFO, so that makedumpfile can assign the offsets
correctly, without needing a VMLINUX.
Also, even along with `cur_cpu_spec->mmu_features` makedumpfile has to
depend on the 'MMU_FTR_TYPE_RADIX' flag in mmu_features, implying kernel
developers need to be cautious of changes to 'MMU_FTR_*' defines.
A more stable approach was suggested in the below thread by contributors:
https://lore.kernel.org/linuxppc-dev/[email protected]/
The suggestion was to add whether 'RADIX_MMU' is enabled in vmcoreinfo
This patch also implements the suggestion, by adding 'RADIX_MMU' in
vmcoreinfo, which makedumpfile can use to get whether the crashed system
had RADIX MMU (in which case 'NUMBER(RADIX_MMU)=1') or not (in which
case 'NUMBER(RADIX_MMU)=0')
Fixes: 368a0590d954 ("powerpc/book3s64/vmemmap: switch radix to use a different vmemmap handling function")
Reported-by: Sachin Sant <[email protected]>
Signed-off-by: Aditya Gupta <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://msgid.link/[email protected]
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