[PATCH v5 3/5] powerpc/crash hp: add crash hotplug support for kexec_file_load
Sourabh Jain
sourabhjain at linux.ibm.com
Mon Jun 20 00:01:04 PDT 2022
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 arch specific crash hotplug
handler.
On the kexec load path, the memsz allocation for the crash FDT segment
is updated to ensure that it has sufficient buffer space to accommodate
future hot add CPUs. Additionally, kimage_arch struct member fdt_index
is initialized with the index of FDT segment in kexec segment array.
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 warns the user and returns.
Signed-off-by: Sourabh Jain <sourabhjain at linux.ibm.com>
---
arch/powerpc/kexec/core_64.c | 49 ++++++++++++++++++++
arch/powerpc/kexec/elf_64.c | 74 +++++++++++++++++++++++++++++++
arch/powerpc/kexec/file_load_64.c | 5 +++
3 files changed, 128 insertions(+)
diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c
index 65b3afb2169a..6d448b55dfad 100644
--- a/arch/powerpc/kexec/core_64.c
+++ b/arch/powerpc/kexec/core_64.c
@@ -465,6 +465,55 @@ int update_cpus_node(void *fdt)
return ret;
}
+#if defined(CONFIG_HOTPLUG_CPU)
+
+int crash_hotplug_support(void) { return 1; }
+
+/**
+ * arch_crash_hotplug_handler() - Handle hotplug kexec segements changes FDT, elfcorehdr
+ * @image: the active struct kimage
+ * @hp_action: the hot un/plug action being handled
+ * @cpu: when KEXEC_CRASH_HP_ADD/REMOVE_CPU, the cpu affected
+ *
+ * To accurately reflect CPU hot un/plug changes, the FDT
+ * must be updated with the new list of CPUs.
+ */
+void arch_crash_handle_hotplug_event(struct kimage *image,
+ unsigned int hp_action, unsigned int cpu)
+
+{
+ 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_info_once("crash hp: crash update is not supported with memory hotplug\n");
+ return;
+ }
+
+ /* Must have valid FDT index */
+ if (!image->arch.fdt_index < 0) {
+ 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
+
#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..8ef18d6c3c32 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -24,6 +24,68 @@
#include <linux/slab.h>
#include <linux/types.h>
+#include <asm/kvm_book3s.h>
+#include <asm/kvm_ppc.h>
+
+#if defined(CONFIG_HOTPLUG_CPU)
+/**
+ * get_cpu_node_sz() - Calculate the space needed to store a CPU device
+ * type node in FDT. The calculation is done based on
+ * the existing CPU node in unflatten device tree. Loop
+ * through all the properties of the very first CPU type
+ * device node found in unflatten device tree and returns
+ * the sum of the property length and property string size
+ * of all properties of a CPU node.
+ */
+static int get_cpu_node_sz(void)
+{
+ struct device_node *dn = NULL;
+ struct property *pp;
+ int cpu_node_size = 0;
+
+ dn = of_find_node_by_type(NULL, "cpu");
+
+ if (!dn) {
+ pr_warn("Unable to locate cpu device_type node.\n");
+ goto out;
+ }
+
+ /* Every node in FDT starts with FDT_BEGIN_NODE and ends with
+ * FDT_END_NODE that takes one byte each.
+ */
+ cpu_node_size = 2;
+
+ for_each_property_of_node(dn, pp) {
+ /**
+ * For each property add two bytes extra. One for string null
+ * character for property name and other for FDT property start
+ * tag FDT_PROP.
+ */
+ cpu_node_size = cpu_node_size + pp->length + strlen(pp->name) + 2;
+ }
+
+out:
+ return cpu_node_size;
+}
+
+/*
+ * get_crash_fdt_mem_sz() - calcuate mem size for crash kernel FDT
+ * @fdt: pointer to crash kernel FDT
+ *
+ * Calculate the buffer space needed to accommodate more CPU nodes in
+ * crash FDT post capture kernel load due to CPU hotplug events.
+ */
+static unsigned int get_crash_fdt_mem_sz(void *fdt)
+{
+ int fdt_cpu_nodes_sz, offline_cpu_cnt;
+
+ offline_cpu_cnt = (num_possible_cpus() - num_present_cpus()) / MAX_SMT_THREADS;
+ fdt_cpu_nodes_sz = get_cpu_node_sz() * offline_cpu_cnt;
+
+ return fdt_totalsize(fdt) + fdt_cpu_nodes_sz;
+}
+#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 +185,18 @@ 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;
+
+#if defined(CONFIG_HOTPLUG_CPU)
+ 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;
+ } else
+#endif
+ {
+ kbuf.memsz = fdt_totalsize(fdt);
+ }
+
ret = kexec_add_buffer(&kbuf);
if (ret)
goto out_free_fdt;
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
index 57f991b0a9da..8345c4f5316d 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -1116,6 +1116,11 @@ int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
return ret;
}
+#if defined(CONFIG_HOTPLUG_CPU)
+ /* Mark fdt_index invalid */
+ image->arch.fdt_index = -1;
+#endif
+
return kexec_image_probe_default(image, buf, buf_len);
}
--
2.36.1
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