Hi Sourabh,
Thanks for fixing this.
Generating an FDT based on of_root (the latest unflattened device-tree) should be ideal as something similar to what is done for /cpus here applies to /memory@* & /ibm,dynamic-reconfiguration-memory nodes too (probably also applies to other nodes like pci@* ?). But IIUC, there is no API in the kernel currently that converts an unflattened device-tree (struct device_node *of_root) to FDT and having one might have it's own challenges.
Should pursue fixing /memory@* and other nodes for kexec as follow-up to this patch either with the unflattened DT to FDT approach or otherwise...
On 17/04/21 11:08 am, Sourabh Jain wrote:
kexec_file_load uses initial_boot_params in setting up the device-tree for the kernel to be loaded. Though initial_boot_params holds info about CPUs at the time of boot, it doesn't account for hot added CPUs.
So, kexec'ing with kexec_file_load syscall would leave the kexec'ed kernel with inaccurate CPU info. Also, if kdump kernel is loaded with kexec_file_load syscall and the system crashes on a hot added CPU, capture kernel hangs failing to identify the boot CPU.
Kernel panic - not syncing: sysrq triggered crash CPU: 24 PID: 6065 Comm: echo Kdump: loaded Not tainted 5.12.0-rc5upstream #54 Call Trace: [c0000000e590fac0] [c0000000007b2400] dump_stack+0xc4/0x114 (unreliable) [c0000000e590fb00] [c000000000145290] panic+0x16c/0x41c [c0000000e590fba0] [c0000000008892e0] sysrq_handle_crash+0x30/0x40 [c0000000e590fc00] [c000000000889cdc] __handle_sysrq+0xcc/0x1f0 [c0000000e590fca0] [c00000000088a538] write_sysrq_trigger+0xd8/0x178 [c0000000e590fce0] [c0000000005e9b7c] proc_reg_write+0x10c/0x1b0 [c0000000e590fd10] [c0000000004f26d0] vfs_write+0xf0/0x330 [c0000000e590fd60] [c0000000004f2aec] ksys_write+0x7c/0x140 [c0000000e590fdb0] [c000000000031ee0] system_call_exception+0x150/0x290 [c0000000e590fe10] [c00000000000ca5c] system_call_common+0xec/0x278 --- interrupt: c00 at 0x7fff905b9664 NIP: 00007fff905b9664 LR: 00007fff905320c4 CTR: 0000000000000000 REGS: c0000000e590fe80 TRAP: 0c00 Not tainted (5.12.0-rc5upstream) MSR: 800000000280f033 <SF,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE> CR: 28000242 XER: 00000000 IRQMASK: 0 GPR00: 0000000000000004 00007ffff5fedf30 00007fff906a7300 0000000000000001 GPR04: 000001002a7355b0 0000000000000002 0000000000000001 00007ffff5fef616 GPR08: 0000000000000001 0000000000000000 0000000000000000 0000000000000000 GPR12: 0000000000000000 00007fff9073a160 0000000000000000 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 GPR20: 0000000000000000 00007fff906a4ee0 0000000000000002 0000000000000001 GPR24: 00007fff906a0898 0000000000000000 0000000000000002 000001002a7355b0 GPR28: 0000000000000002 00007fff906a1790 000001002a7355b0 0000000000000002 NIP [00007fff905b9664] 0x7fff905b9664 LR [00007fff905320c4] 0x7fff905320c4 --- interrupt: c00
To avoid this from happening, extract current CPU info from of_root device node and use it for setting up the fdt in kexec_file_load case.
Fixes: 6ecd0163d360 ("powerpc/kexec_file: Add appropriate regions for memory reserve map")
Signed-off-by: Sourabh Jain sourabhjain@linux.ibm.com Cc: stable@vger.kernel.org
Fow now, this should be a good stop-gap fix for /cpus node case.
Reviewed-by: Hari Bathini hbathini@linux.ibm.com
arch/powerpc/kexec/file_load_64.c | 98 +++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+)
Changelog:
v1 -> v2
- fdt should be updated regardless of kexec type
- updated commit message and title
v2 -> v3
- Fixed warnings reported by patchwork (https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20210416124658.71886...)
- argument aligned to open parenthesis
- declared add_node_prop and update_cpus_node function static
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c index 02b9e4d0dc40..878f8297fbed 100644 --- a/arch/powerpc/kexec/file_load_64.c +++ b/arch/powerpc/kexec/file_load_64.c @@ -960,6 +960,99 @@ unsigned int kexec_fdt_totalsize_ppc64(struct kimage *image) return fdt_size; } +/**
- add_node_prop - Read property from device node structure and add
them to fdt.
- @fdt: Flattened device tree of the kernel
- @node_offset: offset of the node to add a property at
- np: device node pointer
- Returns 0 on success, negative errno on error.
- */
+static int add_node_prop(void *fdt, int node_offset, const struct device_node *np) +{
- int ret = 0;
- struct property *pp;
- unsigned long flags;
- if (!np)
return -EINVAL;- raw_spin_lock_irqsave(&devtree_lock, flags);
- for (pp = np->properties; pp; pp = pp->next) {
ret = fdt_setprop(fdt, node_offset, pp->name,pp->value, pp->length);if (ret < 0) {pr_err("Unable to add %s property: %s\n",pp->name, fdt_strerror(ret));goto out;}- }
+out:
- raw_spin_unlock_irqrestore(&devtree_lock, flags);
- return ret;
+}
+/**
- update_cpus_node - Update cpus node of flattened device-tree using of_root
device node.
- @fdt: Flattened device tree of the kernel.
- Returns 0 on success, negative errno on error.
- */
+static int update_cpus_node(void *fdt) +{
- struct device_node *cpus_node, *dn;
- int cpus_offset, cpus_subnode_off, ret = 0;
- cpus_offset = fdt_path_offset(fdt, "/cpus");
- if (cpus_offset == -FDT_ERR_NOTFOUND || cpus_offset > 0) {
if (cpus_offset > 0) {ret = fdt_del_node(fdt, cpus_offset);if (ret < 0) {pr_err("Error deleting /cpus node: %s\n",fdt_strerror(ret));return -EINVAL;}}/* Add cpus node to fdt */cpus_offset = fdt_add_subnode(fdt, fdt_path_offset(fdt, "/"),"cpus");if (cpus_offset < 0) {pr_err("Error creating /cpus node: %s\n",fdt_strerror(cpus_offset));return -EINVAL;}/* Add cpus node properties */cpus_node = of_find_node_by_path("/cpus");ret = add_node_prop(fdt, cpus_offset, cpus_node);if (ret < 0)return ret;/* Loop through all subnodes of cpus and add them to fdt */for_each_node_by_type(dn, "cpu") {cpus_subnode_off = fdt_add_subnode(fdt,cpus_offset,dn->full_name);if (cpus_subnode_off < 0) {pr_err("Unable to add %s subnode: %s\n",dn->full_name, fdt_strerror(cpus_subnode_off));return cpus_subnode_off;}ret = add_node_prop(fdt, cpus_subnode_off, dn);if (ret < 0)return ret;}- } else if (cpus_offset < 0) {
pr_err("Malformed device tree: error reading /cpus node: %s\n",fdt_strerror(cpus_offset));- }
- return ret;
+}
- /**
- setup_new_fdt_ppc64 - Update the flattend device-tree of the kernel
being loaded.@@ -1020,6 +1113,11 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt, } }
- /* Update cpus nodes information to account hotplug CPUs. */
- ret = update_cpus_node(fdt);
- if (ret < 0)
return ret;- /* Update memory reserve map */ ret = get_reserved_memory_ranges(&rmem); if (ret)