[PATCH v4] powerpc/kexec_file: use current CPU info while setting up FDT
Sourabh Jain
sourabhjain at linux.ibm.com
Tue Apr 20 15:50:10 AEST 2021
On 19/04/21 5:51 pm, Michael Ellerman wrote:
> Hari Bathini <hbathini at linux.ibm.com> writes:
>> On 19/04/21 2:06 pm, 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 at linux.ibm.com>
>>> Reviewed-by: Hari Bathini <hbathini at linux.ibm.com>
>>> Cc: <stable at vger.kernel.org>
>>> ---
>>> arch/powerpc/kexec/file_load_64.c | 98 +++++++++++++++++++++++++++++++
>>> 1 file changed, 98 insertions(+)
>>>
>>> ---
>>> Changelog:
>>>
>>> v1 -> v3
>>> - https://lists.ozlabs.org/pipermail/linuxppc-dev/2021-April/227756.html
>>>
>>> v3 -> v4
>>> - Rearranged if-else statement in update_cpus_node function to avoid
>>> redundant checks for positive cpus_offset.
>>> ---
>>>
>>> diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
>>> index 02b9e4d0dc40..195ef303d530 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 < 0 && cpus_offset != -FDT_ERR_NOTFOUND) {
>>> + pr_err("Malformed device tree: error reading /cpus node: %s\n",
>>> + fdt_strerror(cpus_offset));
>>> + return cpus_offset;
>>> + } else {
>>
>>> + 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;
>>> + }
>> The above code block doesn't really need an explicit else condition..
> Yeah, use the early return to avoid having to indent all the rest of
> that logic.
>
> Please send a v5.
>
> Thanks for the review.
>
> v5 sent.
>
> - Sourabh Jain
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