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Tue, 20 Apr 2021 05:50:16 GMT Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by ppma06ams.nl.ibm.com with ESMTP id 37yt2rsddg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 20 Apr 2021 05:50:15 +0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 13K5oCCc60948826 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 20 Apr 2021 05:50:12 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BF5FA5204F; Tue, 20 Apr 2021 05:50:12 +0000 (GMT) Received: from [9.85.72.203] (unknown [9.85.72.203]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 59A9552050; Tue, 20 Apr 2021 05:50:11 +0000 (GMT) Subject: Re: [PATCH v4] powerpc/kexec_file: use current CPU info while setting up FDT To: Michael Ellerman , Hari Bathini References: <20210419083624.1124390-1-sourabhjain@linux.ibm.com> <3c004e09-7db2-1bb8-352a-0695278eea93@linux.ibm.com> <877dkyea7g.fsf@mpe.ellerman.id.au> From: Sourabh Jain Message-ID: Date: Tue, 20 Apr 2021 11:20:10 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 In-Reply-To: <877dkyea7g.fsf@mpe.ellerman.id.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-TM-AS-GCONF: 00 X-Proofpoint-GUID: aSeYwiKuCk7sdH_RaI8jom6E05NnRjEX X-Proofpoint-ORIG-GUID: aSeYwiKuCk7sdH_RaI8jom6E05NnRjEX Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.761 definitions=2021-04-20_01:2021-04-19, 2021-04-20 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 adultscore=0 spamscore=0 clxscore=1015 priorityscore=1501 suspectscore=0 malwarescore=0 bulkscore=0 phishscore=0 impostorscore=0 mlxscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104200042 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mahesh@linux.vnet.ibm.com, stable@vger.kernel.org, bauerman@linux.ibm.com, linuxppc-dev@ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 19/04/21 5:51 pm, Michael Ellerman wrote: > Hari Bathini 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 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 >>> Reviewed-by: Hari Bathini >>> Cc: >>> --- >>> 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