From: Lianbo Jiang <lijiang@redhat.com> To: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, bhe@redhat.com, dyoung@redhat.com, jgross@suse.com, dhowells@redhat.com, Thomas.Lendacky@amd.com, ebiederm@xmission.com, vgoyal@redhat.com, kexec@lists.infradead.org Subject: [PATCH 1/3 v4] x86/kdump: always reserve the low 1MiB when the crashkernel option is specified Date: Thu, 17 Oct 2019 17:43:45 +0800 [thread overview] Message-ID: <20191017094347.20327-2-lijiang@redhat.com> (raw) In-Reply-To: <20191017094347.20327-1-lijiang@redhat.com> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204793 Kdump kernel will reuse the first 640k region because of some reasons, for example: the trampline and conventional PC system BIOS region may require to allocate memory in this area. Obviously, kdump kernel will also overwrite the first 640k region, therefore, kernel has to copy the contents of the first 640k area to a backup area, which is done in purgatory(), because vmcore may need the old memory. When vmcore is dumped, kdump kernel will read the old memory from the backup area of the first 640k area. Basically, the main reason should be clear, kernel does not correctly handle the first 640k region when SME is active, which causes that kernel does not properly copy these old memory to the backup area in purgatory(). Therefore, kdump kernel reads out the incorrect contents from the backup area when dumping vmcore. Finally, the phenomenon is as follow: [root linux]$ crash vmlinux /var/crash/127.0.0.1-2019-09-19-08\:31\:27/vmcore WARNING: kernel relocated [240MB]: patching 97110 gdb minimal_symbol values KERNEL: /var/crash/127.0.0.1-2019-09-19-08:31:27/vmlinux DUMPFILE: /var/crash/127.0.0.1-2019-09-19-08:31:27/vmcore [PARTIAL DUMP] CPUS: 128 DATE: Thu Sep 19 08:31:18 2019 UPTIME: 00:01:21 LOAD AVERAGE: 0.16, 0.07, 0.02 TASKS: 1343 NODENAME: amd-ethanol RELEASE: 5.3.0-rc7+ VERSION: #4 SMP Thu Sep 19 08:14:00 EDT 2019 MACHINE: x86_64 (2195 Mhz) MEMORY: 127.9 GB PANIC: "Kernel panic - not syncing: sysrq triggered crash" PID: 9789 COMMAND: "bash" TASK: "ffff89711894ae80 [THREAD_INFO: ffff89711894ae80]" CPU: 83 STATE: TASK_RUNNING (PANIC) crash> kmem -s|grep -i invalid kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4 kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4 crash> BTW: I also tried to fix the above problem in purgatory(), but there are too many restricts in purgatory() context, for example: i can't allocate new memory to create the identity mapping page table for SME situation. Currently, there are two places where the first 640k area is needed, the first one is in the find_trampoline_placement(), another one is in the reserve_real_mode(), and their content doesn't matter. To avoid the above error, when the crashkernel kernel command line option is specified, lets reserve the remaining low 1MiB memory( after reserving real mode memroy) so that the allocated memory does not fall into the low 1MiB area, which makes us not to copy the first 640k content to a backup region in purgatory(). This indicates that it does not need to be included in crash dumps or used for anything execept the processor trampolines that must live in the low 1MiB. In addition, also need to clean all the code related to the backup region later. Signed-off-by: Lianbo Jiang <lijiang@redhat.com> --- arch/x86/realmode/init.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c index 7dce39c8c034..1f0492830f2c 100644 --- a/arch/x86/realmode/init.c +++ b/arch/x86/realmode/init.c @@ -34,6 +34,17 @@ void __init reserve_real_mode(void) memblock_reserve(mem, size); set_real_mode_mem(mem); + +#ifdef CONFIG_KEXEC_CORE + /* + * When the crashkernel option is specified, only use the low + * 1MiB for the real mode trampoline. + */ + if (strstr(boot_command_line, "crashkernel=")) { + memblock_reserve(0, 1<<20); + pr_info("Reserving the low 1MiB of memory for crashkernel\n"); + } +#endif /* CONFIG_KEXEC_CORE */ } static void __init setup_real_mode(void) -- 2.17.1
WARNING: multiple messages have this Message-ID (diff)
From: Lianbo Jiang <lijiang@redhat.com> To: linux-kernel@vger.kernel.org Cc: jgross@suse.com, Thomas.Lendacky@amd.com, bhe@redhat.com, x86@kernel.org, kexec@lists.infradead.org, dhowells@redhat.com, mingo@redhat.com, bp@alien8.de, ebiederm@xmission.com, hpa@zytor.com, tglx@linutronix.de, dyoung@redhat.com, vgoyal@redhat.com Subject: [PATCH 1/3 v4] x86/kdump: always reserve the low 1MiB when the crashkernel option is specified Date: Thu, 17 Oct 2019 17:43:45 +0800 [thread overview] Message-ID: <20191017094347.20327-2-lijiang@redhat.com> (raw) In-Reply-To: <20191017094347.20327-1-lijiang@redhat.com> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204793 Kdump kernel will reuse the first 640k region because of some reasons, for example: the trampline and conventional PC system BIOS region may require to allocate memory in this area. Obviously, kdump kernel will also overwrite the first 640k region, therefore, kernel has to copy the contents of the first 640k area to a backup area, which is done in purgatory(), because vmcore may need the old memory. When vmcore is dumped, kdump kernel will read the old memory from the backup area of the first 640k area. Basically, the main reason should be clear, kernel does not correctly handle the first 640k region when SME is active, which causes that kernel does not properly copy these old memory to the backup area in purgatory(). Therefore, kdump kernel reads out the incorrect contents from the backup area when dumping vmcore. Finally, the phenomenon is as follow: [root linux]$ crash vmlinux /var/crash/127.0.0.1-2019-09-19-08\:31\:27/vmcore WARNING: kernel relocated [240MB]: patching 97110 gdb minimal_symbol values KERNEL: /var/crash/127.0.0.1-2019-09-19-08:31:27/vmlinux DUMPFILE: /var/crash/127.0.0.1-2019-09-19-08:31:27/vmcore [PARTIAL DUMP] CPUS: 128 DATE: Thu Sep 19 08:31:18 2019 UPTIME: 00:01:21 LOAD AVERAGE: 0.16, 0.07, 0.02 TASKS: 1343 NODENAME: amd-ethanol RELEASE: 5.3.0-rc7+ VERSION: #4 SMP Thu Sep 19 08:14:00 EDT 2019 MACHINE: x86_64 (2195 Mhz) MEMORY: 127.9 GB PANIC: "Kernel panic - not syncing: sysrq triggered crash" PID: 9789 COMMAND: "bash" TASK: "ffff89711894ae80 [THREAD_INFO: ffff89711894ae80]" CPU: 83 STATE: TASK_RUNNING (PANIC) crash> kmem -s|grep -i invalid kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4 kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4 crash> BTW: I also tried to fix the above problem in purgatory(), but there are too many restricts in purgatory() context, for example: i can't allocate new memory to create the identity mapping page table for SME situation. Currently, there are two places where the first 640k area is needed, the first one is in the find_trampoline_placement(), another one is in the reserve_real_mode(), and their content doesn't matter. To avoid the above error, when the crashkernel kernel command line option is specified, lets reserve the remaining low 1MiB memory( after reserving real mode memroy) so that the allocated memory does not fall into the low 1MiB area, which makes us not to copy the first 640k content to a backup region in purgatory(). This indicates that it does not need to be included in crash dumps or used for anything execept the processor trampolines that must live in the low 1MiB. In addition, also need to clean all the code related to the backup region later. Signed-off-by: Lianbo Jiang <lijiang@redhat.com> --- arch/x86/realmode/init.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c index 7dce39c8c034..1f0492830f2c 100644 --- a/arch/x86/realmode/init.c +++ b/arch/x86/realmode/init.c @@ -34,6 +34,17 @@ void __init reserve_real_mode(void) memblock_reserve(mem, size); set_real_mode_mem(mem); + +#ifdef CONFIG_KEXEC_CORE + /* + * When the crashkernel option is specified, only use the low + * 1MiB for the real mode trampoline. + */ + if (strstr(boot_command_line, "crashkernel=")) { + memblock_reserve(0, 1<<20); + pr_info("Reserving the low 1MiB of memory for crashkernel\n"); + } +#endif /* CONFIG_KEXEC_CORE */ } static void __init setup_real_mode(void) -- 2.17.1 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
next prev parent reply other threads:[~2019-10-17 9:44 UTC|newest] Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-17 9:43 [PATCH 0/3 v4] x86/kdump: Fix 'kmem -s' reported an invalid freepointer when SME was active Lianbo Jiang 2019-10-17 9:43 ` Lianbo Jiang 2019-10-17 9:43 ` Lianbo Jiang [this message] 2019-10-17 9:43 ` [PATCH 1/3 v4] x86/kdump: always reserve the low 1MiB when the crashkernel option is specified Lianbo Jiang 2019-10-22 8:30 ` Borislav Petkov 2019-10-22 8:30 ` Borislav Petkov 2019-10-23 5:23 ` lijiang 2019-10-23 5:23 ` lijiang 2019-10-23 7:43 ` Borislav Petkov 2019-10-23 7:43 ` Borislav Petkov 2019-10-23 5:35 ` lijiang 2019-10-23 5:35 ` lijiang 2019-10-23 7:46 ` Borislav Petkov 2019-10-23 7:46 ` Borislav Petkov 2019-10-23 9:20 ` lijiang 2019-10-23 9:20 ` lijiang 2019-10-24 8:13 ` d.hatayama 2019-10-24 8:13 ` d.hatayama 2019-10-24 9:10 ` Borislav Petkov 2019-10-24 9:10 ` Borislav Petkov 2019-10-24 11:24 ` lijiang 2019-10-24 11:24 ` lijiang 2019-10-24 22:12 ` [PATCH] x86/kdump: always reserve the low 1MiB when the crashkernel kbuild test robot 2019-10-24 22:12 ` kbuild test robot 2019-10-24 22:12 ` kbuild test robot 2019-10-24 23:55 ` lijiang 2019-10-24 23:55 ` lijiang 2019-10-24 23:55 ` lijiang 2019-10-17 9:43 ` [PATCH 2/3 v4] x86/kdump: remove the unused crash_copy_backup_region() Lianbo Jiang 2019-10-17 9:43 ` Lianbo Jiang 2019-10-17 9:43 ` [PATCH 3/3 v4] x86/kdump: clean up all the code related to the backup region Lianbo Jiang 2019-10-17 9:43 ` Lianbo Jiang 2019-10-22 12:15 ` Borislav Petkov 2019-10-22 12:15 ` Borislav Petkov [not found] <mailman.5359.1571746554.2486.kexec@lists.infradead.org> 2019-10-22 13:38 ` [PATCH 1/3 v4] x86/kdump: always reserve the low 1MiB when the crashkernel option is specified Dave Anderson [not found] <55902207.7797907.1571751831873.JavaMail.zimbra@redhat.com> 2019-10-22 13:43 ` Dave Anderson
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