[PATCH 0/2 RESEND v8] x86/kdump: Fix 'kmem -s' reported an invalid freepointer when SME was active

[PATCH 0/2 RESEND v8] x86/kdump: Fix 'kmem -s' reported an invalid freepointer when SME was active

[Lianbo Jiang]

In purgatory(), the main things are as below:

[1] verify sha256 hashes for various segments.
    Lets keep these codes, and do not touch the logic.

[2] copy the first 640k content to a backup region.
    Lets safely remove it and clean all code related to backup region.

This patch series will remove the backup region, because the current
handling of copying the first 640k runs into problems when SME is
active(https://bugzilla.kernel.org/show_bug.cgi?id=204793).

The low 1M region will always be reserved when the crashkernel kernel
command line option is specified. And this way makes it unnecessary to
do anything with the low 1M region, because the memory allocated later
won't fall into the low 1M area.

This series includes two patches:
[1] x86/kdump: always reserve the low 1M when the crashkernel option
    is specified
    The low 1M region will always be reserved when the crashkernel
    kernel command line option is specified, which ensures that the
    memory allocated later won't fall into the low 1M area.

[2] x86/kdump: clean up all the code related to the backup region
    Remove the backup region and clean up.

Changes since v1:
[1] Add extra checking condition: when the crashkernel option is
    specified, reserve the low 640k area.

Changes since v2:
[1] Reserve the low 1M region when the crashkernel option is only
    specified.(Suggested by Eric)

[2] Remove the unused crash_copy_backup_region()

[3] Remove the backup region and clean up

[4] Split them into three patches

Changes since v3:
[1] Improve the first patch's log

[2] Improve the third patch based on Eric's suggestions

Changes since v4:
[1] Correct some typos, and also improve the first patch's log

[2] Add a new function kexec_reserve_low_1MiB() in kernel/kexec_core.c
    and which is called by reserve_real_mode(). (Suggested by Boris)

Changes since v5:
[1] Call the cmdline_find_option() instead of strstr() to check the
    crashkernel option. (Suggested by Hatayama)

[2] Add a weak function kexec_reserve_low_1MiB() in kernel/kexec_core.c,
    and implement the kexec_reserve_low_1MiB() in arch/x86/kernel/
    machine_kexec_64.c so that it does not cause the compile error
    on non-x86 kernel, and also ensures that it can work well on x86
    kernel.

Changes since v6:
[1] Move the kexec_reserve_low_1MiB() to arch/x86/kernel/crash.c and
    also move its declaration function to arch/x86/include/asm/crash.h
    (Suggested by Dave Young)

[2] Adjust the corresponding header files.

Changes since v7:
[1] Change the function name from kexec_reserve_low_1MiB() to
    crash_reserve_low_1M().

[2] Fix some warnings reported by kduild.

Lianbo Jiang (2):
  x86/kdump: always reserve the low 1M when the crashkernel option is
    specified
  x86/kdump: clean up all the code related to the backup region

 arch/x86/include/asm/crash.h       |   8 +++
 arch/x86/include/asm/kexec.h       |  10 ---
 arch/x86/include/asm/purgatory.h   |  10 ---
 arch/x86/kernel/crash.c            | 102 ++++++++---------------------
 arch/x86/kernel/machine_kexec_64.c |  47 -------------
 arch/x86/purgatory/purgatory.c     |  19 ------
 arch/x86/realmode/init.c           |   2 +
 7 files changed, 36 insertions(+), 162 deletions(-)

-- 
2.17.1

[PATCH 1/2 RESEND v8] x86/kdump: always reserve the low 1M when the crashkernel option is specified

[Lianbo Jiang]

Kdump kernel will reuse the first 640k region because the real mode
trampoline has to work in this area. When the vmcore is dumped, the
old memory in this area may be accessed, therefore, kernel has to
copy the contents of the first 640k area to a backup region so that
kdump kernel can read the old memory from the backup area of the
first 640k area, which is done in the purgatory().

But, the current handling of copying the first 640k area runs into
problems when SME is enabled, kernel does not properly copy these
old memory to the backup area in the purgatory(), thereby, kdump
kernel reads out the encrypted contents, because the kdump kernel
must access the first kernel's memory with the encryption bit set
when SME is enabled in the first kernel. Please refer to this link:

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204793

Finally, it causes the following errors, and the crash tool gets
invalid pointers when parsing the vmcore.

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>

To avoid the above errors, when the crashkernel option is specified,
lets reserve the remaining low 1M memory(after reserving real mode
memory) so that the allocated memory does not fall into the low 1M
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 except the processor
trampolines that must live in the low 1M.

Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
Reported-by: kbuild test robot <lkp@intel.com>
---
 arch/x86/include/asm/crash.h |  8 ++++++++
 arch/x86/kernel/crash.c      | 15 +++++++++++++++
 arch/x86/realmode/init.c     |  2 ++
 3 files changed, 25 insertions(+)

diff --git a/arch/x86/include/asm/crash.h b/arch/x86/include/asm/crash.h
index 0acf5ee45a21..88eadd08ad70 100644
--- a/arch/x86/include/asm/crash.h
+++ b/arch/x86/include/asm/crash.h
@@ -2,10 +2,18 @@
 #ifndef _ASM_X86_CRASH_H
 #define _ASM_X86_CRASH_H
 
+struct kimage;
+
 int crash_load_segments(struct kimage *image);
 int crash_copy_backup_region(struct kimage *image);
 int crash_setup_memmap_entries(struct kimage *image,
 		struct boot_params *params);
 void crash_smp_send_stop(void);
 
+#ifdef CONFIG_KEXEC_CORE
+void __init crash_reserve_low_1M(void);
+#else
+static inline void __init crash_reserve_low_1M(void) { }
+#endif
+
 #endif /* _ASM_X86_CRASH_H */
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index eb651fbde92a..db2301afade5 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -24,6 +24,7 @@
 #include <linux/export.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
+#include <linux/memblock.h>
 
 #include <asm/processor.h>
 #include <asm/hardirq.h>
@@ -39,6 +40,7 @@
 #include <asm/virtext.h>
 #include <asm/intel_pt.h>
 #include <asm/crash.h>
+#include <asm/cmdline.h>
 
 /* Used while preparing memory map entries for second kernel */
 struct crash_memmap_data {
@@ -68,6 +70,19 @@ static inline void cpu_crash_vmclear_loaded_vmcss(void)
 	rcu_read_unlock();
 }
 
+/*
+ * When the crashkernel option is specified, only use the low
+ * 1M for the real mode trampoline.
+ */
+void __init crash_reserve_low_1M(void)
+{
+	if (cmdline_find_option(boot_command_line, "crashkernel",
+				NULL, 0) > 0) {
+		memblock_reserve(0, 1<<20);
+		pr_info("Reserving the low 1M of memory for crashkernel\n");
+	}
+}
+
 #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
 
 static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
index 7dce39c8c034..262f83cad355 100644
--- a/arch/x86/realmode/init.c
+++ b/arch/x86/realmode/init.c
@@ -8,6 +8,7 @@
 #include <asm/pgtable.h>
 #include <asm/realmode.h>
 #include <asm/tlbflush.h>
+#include <asm/crash.h>
 
 struct real_mode_header *real_mode_header;
 u32 *trampoline_cr4_features;
@@ -34,6 +35,7 @@ void __init reserve_real_mode(void)
 
 	memblock_reserve(mem, size);
 	set_real_mode_mem(mem);
+	crash_reserve_low_1M();
 }
 
 static void __init setup_real_mode(void)
-- 
2.17.1

[PATCH 2/2 RESEND v8] x86/kdump: clean up all the code related to the backup region

[Lianbo Jiang]

When the crashkernel kernel command line option is specified, the
low 1M memory will always be reserved, which makes that the memory
allocated later won't fall into the low 1M area, thereby, it's not
necessary to create a backup region and also no need to copy the
first 640k content to a backup region.

Currently, the code related to the backup region can be safely
removed, so lets clean up.

Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
---
 arch/x86/include/asm/kexec.h       | 10 ----
 arch/x86/include/asm/purgatory.h   | 10 ----
 arch/x86/kernel/crash.c            | 87 ++++--------------------------
 arch/x86/kernel/machine_kexec_64.c | 47 ----------------
 arch/x86/purgatory/purgatory.c     | 19 -------
 5 files changed, 11 insertions(+), 162 deletions(-)

diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index 5e7d6b46de97..6802c59e8252 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -66,10 +66,6 @@ struct kimage;
 # define KEXEC_ARCH KEXEC_ARCH_X86_64
 #endif
 
-/* Memory to backup during crash kdump */
-#define KEXEC_BACKUP_SRC_START	(0UL)
-#define KEXEC_BACKUP_SRC_END	(640 * 1024UL - 1)	/* 640K */
-
 /*
  * This function is responsible for capturing register states if coming
  * via panic otherwise just fix up the ss and sp if coming via kernel
@@ -154,12 +150,6 @@ struct kimage_arch {
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
-	/* Details of backup region */
-	unsigned long backup_src_start;
-	unsigned long backup_src_sz;
-
-	/* Physical address of backup segment */
-	unsigned long backup_load_addr;
 
 	/* Core ELF header buffer */
 	void *elf_headers;
diff --git a/arch/x86/include/asm/purgatory.h b/arch/x86/include/asm/purgatory.h
index 92c34e517da1..5528e9325049 100644
--- a/arch/x86/include/asm/purgatory.h
+++ b/arch/x86/include/asm/purgatory.h
@@ -6,16 +6,6 @@
 #include <linux/purgatory.h>
 
 extern void purgatory(void);
-/*
- * These forward declarations serve two purposes:
- *
- * 1) Make sparse happy when checking arch/purgatory
- * 2) Document that these are required to be global so the symbol
- *    lookup in kexec works
- */
-extern unsigned long purgatory_backup_dest;
-extern unsigned long purgatory_backup_src;
-extern unsigned long purgatory_backup_sz;
 #endif	/* __ASSEMBLY__ */
 
 #endif /* _ASM_PURGATORY_H */
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index db2301afade5..40b04b6eb675 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -188,8 +188,6 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
 
 #ifdef CONFIG_KEXEC_FILE
 
-static unsigned long crash_zero_bytes;
-
 static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
 {
 	unsigned int *nr_ranges = arg;
@@ -232,6 +230,11 @@ static int elf_header_exclude_ranges(struct crash_mem *cmem)
 {
 	int ret = 0;
 
+	/* Exclude the low 1M because it is always reserved */
+	ret = crash_exclude_mem_range(cmem, 0, 1<<20);
+	if (ret)
+		return ret;
+
 	/* Exclude crashkernel region */
 	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
 	if (ret)
@@ -261,9 +264,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
 					unsigned long *sz)
 {
 	struct crash_mem *cmem;
-	Elf64_Ehdr *ehdr;
-	Elf64_Phdr *phdr;
-	int ret, i;
+	int ret;
 
 	cmem = fill_up_crash_elf_data();
 	if (!cmem)
@@ -282,22 +283,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
 	/* By default prepare 64bit headers */
 	ret =  crash_prepare_elf64_headers(cmem,
 				IS_ENABLED(CONFIG_X86_64), addr, sz);
-	if (ret)
-		goto out;
 
-	/*
-	 * If a range matches backup region, adjust offset to backup
-	 * segment.
-	 */
-	ehdr = (Elf64_Ehdr *)*addr;
-	phdr = (Elf64_Phdr *)(ehdr + 1);
-	for (i = 0; i < ehdr->e_phnum; phdr++, i++)
-		if (phdr->p_type == PT_LOAD &&
-				phdr->p_paddr == image->arch.backup_src_start &&
-				phdr->p_memsz == image->arch.backup_src_sz) {
-			phdr->p_offset = image->arch.backup_load_addr;
-			break;
-		}
 out:
 	vfree(cmem);
 	return ret;
@@ -336,19 +322,11 @@ static int memmap_exclude_ranges(struct kimage *image, struct crash_mem *cmem,
 				 unsigned long long mend)
 {
 	unsigned long start, end;
-	int ret = 0;
 
 	cmem->ranges[0].start = mstart;
 	cmem->ranges[0].end = mend;
 	cmem->nr_ranges = 1;
 
-	/* Exclude Backup region */
-	start = image->arch.backup_load_addr;
-	end = start + image->arch.backup_src_sz - 1;
-	ret = crash_exclude_mem_range(cmem, start, end);
-	if (ret)
-		return ret;
-
 	/* Exclude elf header region */
 	start = image->arch.elf_load_addr;
 	end = start + image->arch.elf_headers_sz - 1;
@@ -371,11 +349,11 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
 	memset(&cmd, 0, sizeof(struct crash_memmap_data));
 	cmd.params = params;
 
-	/* Add first 640K segment */
-	ei.addr = image->arch.backup_src_start;
-	ei.size = image->arch.backup_src_sz;
-	ei.type = E820_TYPE_RAM;
-	add_e820_entry(params, &ei);
+	/* Add the low 1M */
+	cmd.type = E820_TYPE_RAM;
+	flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+	walk_iomem_res_desc(IORES_DESC_NONE, flags, 0, (1<<20)-1, &cmd,
+			memmap_entry_callback);
 
 	/* Add ACPI tables */
 	cmd.type = E820_TYPE_ACPI;
@@ -424,55 +402,12 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
 	return ret;
 }
 
-static int determine_backup_region(struct resource *res, void *arg)
-{
-	struct kimage *image = arg;
-
-	image->arch.backup_src_start = res->start;
-	image->arch.backup_src_sz = resource_size(res);
-
-	/* Expecting only one range for backup region */
-	return 1;
-}
-
 int crash_load_segments(struct kimage *image)
 {
 	int ret;
 	struct kexec_buf kbuf = { .image = image, .buf_min = 0,
 				  .buf_max = ULONG_MAX, .top_down = false };
 
-	/*
-	 * Determine and load a segment for backup area. First 640K RAM
-	 * region is backup source
-	 */
-
-	ret = walk_system_ram_res(KEXEC_BACKUP_SRC_START, KEXEC_BACKUP_SRC_END,
-				image, determine_backup_region);
-
-	/* Zero or postive return values are ok */
-	if (ret < 0)
-		return ret;
-
-	/* Add backup segment. */
-	if (image->arch.backup_src_sz) {
-		kbuf.buffer = &crash_zero_bytes;
-		kbuf.bufsz = sizeof(crash_zero_bytes);
-		kbuf.memsz = image->arch.backup_src_sz;
-		kbuf.buf_align = PAGE_SIZE;
-		/*
-		 * Ideally there is no source for backup segment. This is
-		 * copied in purgatory after crash. Just add a zero filled
-		 * segment for now to make sure checksum logic works fine.
-		 */
-		ret = kexec_add_buffer(&kbuf);
-		if (ret)
-			return ret;
-		image->arch.backup_load_addr = kbuf.mem;
-		pr_debug("Loaded backup region at 0x%lx backup_start=0x%lx memsz=0x%lx\n",
-			 image->arch.backup_load_addr,
-			 image->arch.backup_src_start, kbuf.memsz);
-	}
-
 	/* Prepare elf headers and add a segment */
 	ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz);
 	if (ret)
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 5dcd438ad8f2..16e125a50b33 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -298,48 +298,6 @@ static void load_segments(void)
 		);
 }
 
-#ifdef CONFIG_KEXEC_FILE
-/* Update purgatory as needed after various image segments have been prepared */
-static int arch_update_purgatory(struct kimage *image)
-{
-	int ret = 0;
-
-	if (!image->file_mode)
-		return 0;
-
-	/* Setup copying of backup region */
-	if (image->type == KEXEC_TYPE_CRASH) {
-		ret = kexec_purgatory_get_set_symbol(image,
-				"purgatory_backup_dest",
-				&image->arch.backup_load_addr,
-				sizeof(image->arch.backup_load_addr), 0);
-		if (ret)
-			return ret;
-
-		ret = kexec_purgatory_get_set_symbol(image,
-				"purgatory_backup_src",
-				&image->arch.backup_src_start,
-				sizeof(image->arch.backup_src_start), 0);
-		if (ret)
-			return ret;
-
-		ret = kexec_purgatory_get_set_symbol(image,
-				"purgatory_backup_sz",
-				&image->arch.backup_src_sz,
-				sizeof(image->arch.backup_src_sz), 0);
-		if (ret)
-			return ret;
-	}
-
-	return ret;
-}
-#else /* !CONFIG_KEXEC_FILE */
-static inline int arch_update_purgatory(struct kimage *image)
-{
-	return 0;
-}
-#endif /* CONFIG_KEXEC_FILE */
-
 int machine_kexec_prepare(struct kimage *image)
 {
 	unsigned long start_pgtable;
@@ -353,11 +311,6 @@ int machine_kexec_prepare(struct kimage *image)
 	if (result)
 		return result;
 
-	/* update purgatory as needed */
-	result = arch_update_purgatory(image);
-	if (result)
-		return result;
-
 	return 0;
 }
 
diff --git a/arch/x86/purgatory/purgatory.c b/arch/x86/purgatory/purgatory.c
index 3b95410ff0f8..2961234d0795 100644
--- a/arch/x86/purgatory/purgatory.c
+++ b/arch/x86/purgatory/purgatory.c
@@ -14,28 +14,10 @@
 
 #include "../boot/string.h"
 
-unsigned long purgatory_backup_dest __section(.kexec-purgatory);
-unsigned long purgatory_backup_src __section(.kexec-purgatory);
-unsigned long purgatory_backup_sz __section(.kexec-purgatory);
-
 u8 purgatory_sha256_digest[SHA256_DIGEST_SIZE] __section(.kexec-purgatory);
 
 struct kexec_sha_region purgatory_sha_regions[KEXEC_SEGMENT_MAX] __section(.kexec-purgatory);
 
-/*
- * On x86, second kernel requries first 640K of memory to boot. Copy
- * first 640K to a backup region in reserved memory range so that second
- * kernel can use first 640K.
- */
-static int copy_backup_region(void)
-{
-	if (purgatory_backup_dest) {
-		memcpy((void *)purgatory_backup_dest,
-		       (void *)purgatory_backup_src, purgatory_backup_sz);
-	}
-	return 0;
-}
-
 static int verify_sha256_digest(void)
 {
 	struct kexec_sha_region *ptr, *end;
@@ -66,7 +48,6 @@ void purgatory(void)
 		for (;;)
 			;
 	}
-	copy_backup_region();
 }
 
 /*
-- 
2.17.1

Re: [PATCH 1/2 RESEND v8] x86/kdump: always reserve the low 1M when the crashkernel option is specified

[Borislav Petkov]

On Thu, Oct 31, 2019 at 11:35:16AM +0800, Lianbo Jiang wrote:
> Kdump kernel will reuse the first 640k region because the real mode
> trampoline has to work in this area. When the vmcore is dumped, the
> old memory in this area may be accessed, therefore, kernel has to
> copy the contents of the first 640k area to a backup region so that
> kdump kernel can read the old memory from the backup area of the
> first 640k area, which is done in the purgatory().
> 
> But, the current handling of copying the first 640k area runs into
> problems when SME is enabled, kernel does not properly copy these
> old memory to the backup area in the purgatory(), thereby, kdump
> kernel reads out the encrypted contents, because the kdump kernel
> must access the first kernel's memory with the encryption bit set
> when SME is enabled in the first kernel. Please refer to this link:
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204793
> 
> Finally, it causes the following errors, and the crash tool gets
> invalid pointers when parsing the vmcore.
> 
> 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>
> 
> To avoid the above errors, when the crashkernel option is specified,
> lets reserve the remaining low 1M memory(after reserving real mode
> memory) so that the allocated memory does not fall into the low 1M
> 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 except the processor
> trampolines that must live in the low 1M.
> 
> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
> Reported-by: kbuild test robot <lkp@intel.com>

Please do not merge a 0day bot fix with another patch of yours which
does not cause it in the first place. When you look at this patch alone,
what do you think the Reported-by tag means, if anything at all?

Also, it is not a "RESEND" if you change them. You can call them v8.1 or
whatever to denote that the change is small.

Also, do not send v9 or v8.1 or whatever, immediately but wait for other
reviews. You have sent these patches 4(!) times in this week alone. How
would you feel if I hammer your inbox with patches on a daily basis?

You can read

https://www.kernel.org/doc/html/latest/process/submitting-patches.html

in the meantime, especially section

"9) Don't get discouraged - or impatient"

while waiting.

Thx.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--

Re: [PATCH 1/2 RESEND v8] x86/kdump: always reserve the low 1M when the crashkernel option is specified

[lijiang]

在 2019年10月31日 15:13, Borislav Petkov 写道:
> Please do not merge a 0day bot fix with another patch of yours which
> does not cause it in the first place. When you look at this patch alone,
> what do you think the Reported-by tag means, if anything at all?
> 
Thanks for your suggestions.

Maybe it should be a separate patch to fix the old compile warnings as follow.
And i should put the patch into this series.


commit d2091d1f4f67f1c38293b0e93fdbfefa766940cf (HEAD -> master)
Author: Lianbo Jiang <lijiang@redhat.com>
Date:   Thu Oct 31 15:48:02 2019 +0800

    kexec: Fix i386 build warnings that missed declaration of struct kimage
    
    Kbuild test robot reported some build warnings, please refer to the
    Link below for details.
    
    Add a declaration of struct kimage to fix these compile warnings.
    
    Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call")
    Reported-by: kbuild test robot <lkp@intel.com>
    Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
    Link: https://lkml.org/lkml/2019/10/30/833

diff --git a/arch/x86/include/asm/crash.h b/arch/x86/include/asm/crash.h
index 0acf5ee45a21..ef5638f641f2 100644
--- a/arch/x86/include/asm/crash.h
+++ b/arch/x86/include/asm/crash.h
@@ -2,6 +2,8 @@
 #ifndef _ASM_X86_CRASH_H
 #define _ASM_X86_CRASH_H
 
+struct kimage;
+
 int crash_load_segments(struct kimage *image);
 int crash_copy_backup_region(struct kimage *image);
 int crash_setup_memmap_entries(struct kimage *image,

> Also, it is not a "RESEND" if you change them. You can call them v8.1 or
> whatever to denote that the change is small.
> 
Thanks for your explanation in detail.

> Also, do not send v9 or v8.1 or whatever, immediately but wait for other
> reviews.

OK. Lets wait a week or more.

> You have sent these patches 4(!) times in this week alone. How
> would you feel if I hammer your inbox with patches on a daily basis?
>Probably because the change is small.

Anyway, so sorry, it seems inconsiderate.

> You can read
> 
> https://www.kernel.org/doc/html/latest/process/submitting-patches.html
> 
> in the meantime, especially section
> 
> "9) Don't get discouraged - or impatient"
> 
> while waiting.

OK. Thanks.

Lianbo

Re: [PATCH 1/2 RESEND v8] x86/kdump: always reserve the low 1M when the crashkernel option is specified

[Borislav Petkov]

On Thu, Oct 31, 2019 at 05:40:35PM +0800, lijiang wrote:
> Maybe it should be a separate patch to fix the old compile warnings as follow.
> And i should put the patch into this series.

Yes, maybe.

> commit d2091d1f4f67f1c38293b0e93fdbfefa766940cf (HEAD -> master)
> Author: Lianbo Jiang <lijiang@redhat.com>
> Date:   Thu Oct 31 15:48:02 2019 +0800
> 
>     kexec: Fix i386 build warnings that missed declaration of struct kimage
>     
>     Kbuild test robot reported some build warnings, please refer to the
>     Link below for details.

Explain here what the warnings are, why they trigger and how you're
fixing it. How a commit message should look like is also explained in
that document I pointed you at.

Refering to some link is not what we do in commit messages.

>     Add a declaration of struct kimage to fix these compile warnings.
>     
>     Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call")
>     Reported-by: kbuild test robot <lkp@intel.com>
>     Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
>     Link: https://lkml.org/lkml/2019/10/30/833

*NEVER* use lkml.org or any other external URL for refering to mail
threads but *always* use our own

lkml.kernel.org/r/<Message-ID>

redirector. See other tip commits for an example.

> > You can read
> > 
> > https://www.kernel.org/doc/html/latest/process/submitting-patches.html
> > 
> > in the meantime, especially section
> > 
> > "9) Don't get discouraged - or impatient"
> > 
> > while waiting.
> 
> OK. Thanks.

And make sure to read that whole document and also have a look at the
process document

https://www.kernel.org/doc/html/latest/process/index.html

so that you can avoid such mistakes in the future.

Thx.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--

Re: [PATCH 1/2 RESEND v8] x86/kdump: always reserve the low 1M when the crashkernel option is specified

[lijiang]

在 2019年10月31日 18:47, Borislav Petkov 写道:
> On Thu, Oct 31, 2019 at 05:40:35PM +0800, lijiang wrote:
>> Maybe it should be a separate patch to fix the old compile warnings as follow.
>> And i should put the patch into this series.
> 
> Yes, maybe.
> 
>> commit d2091d1f4f67f1c38293b0e93fdbfefa766940cf (HEAD -> master)
>> Author: Lianbo Jiang <lijiang@redhat.com>
>> Date:   Thu Oct 31 15:48:02 2019 +0800
>>
>>     kexec: Fix i386 build warnings that missed declaration of struct kimage
>>     
>>     Kbuild test robot reported some build warnings, please refer to the
>>     Link below for details.
> 
> Explain here what the warnings are, why they trigger and how you're
> fixing it. How a commit message should look like is also explained in
> that document I pointed you at.
> 

OK, looks better('what-why-how'). I will improve the above log.

> Refering to some link is not what we do in commit messages.
> 
>>     Add a declaration of struct kimage to fix these compile warnings.
>>     
>>     Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call")
>>     Reported-by: kbuild test robot <lkp@intel.com>
>>     Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
>>     Link: https://lkml.org/lkml/2019/10/30/833
> 
> *NEVER* use lkml.org or any other external URL for refering to mail
> threads but *always* use our own
> 
> lkml.kernel.org/r/<Message-ID>
> 
> redirector. See other tip commits for an example.
> 

It's useful to me. Thanks.

>>> You can read
>>>
>>> https://www.kernel.org/doc/html/latest/process/submitting-patches.html
>>>
>>> in the meantime, especially section
>>>
>>> "9) Don't get discouraged - or impatient"
>>>
>>> while waiting.
>>
>> OK. Thanks.
> 
> And make sure to read that whole document and also have a look at the
> process document
> 

I will read the above document carefully. But some of the rules in the document are
still easy to be forgot, maybe need to practice repeatedly.

> https://www.kernel.org/doc/html/latest/process/index.html
> 
> so that you can avoid such mistakes in the future.
> 

Good suggestions. Thank you so much.

Lianbo

> Thx.
>