linux-kernel - [PATCH] crash_dump: remove saved_max

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Date:   Tue, 31 Mar 2020 02:15:44 +0800
From:   Kairui Song <kasong@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Young <dyoung@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        kexec@...ts.infradead.org, Kairui Song <kasong@...hat.com>
Subject: [PATCH] crash_dump: remove saved_max_pfn

This variable is no longer used.

saved_max_pfn was originally introduce in commit 92aa63a5a1bf ("[PATCH]
kdump: Retrieve saved max pfn"), used to make sure that user does not
try to read the physical memory beyond saved_max_pfn. But since
commit 921d58c0e699 ("vmcore: remove saved_max_pfn check")
it's no longer used for the check.

Only user left is Calary IOMMU, which start using it from
commit 95b68dec0d52 ("calgary iommu: use the first kernels TCE tables
in kdump"). But again, recently in commit 90dc392fc445 ("x86: Remove
the calgary IOMMU driver"), Calary IOMMU is removed and this variable
no longer have any user.

So just remove it.

Signed-off-by: Kairui Song <kasong@...hat.com>
---
 arch/x86/kernel/e820.c     | 8 --------
 include/linux/crash_dump.h | 2 --
 kernel/crash_dump.c        | 6 ------
 3 files changed, 16 deletions(-)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index c5399e80c59c..4d13c57f370a 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -910,14 +910,6 @@ static int __init parse_memmap_one(char *p)
 		return -EINVAL;
 
 	if (!strncmp(p, "exactmap", 8)) {
-#ifdef CONFIG_CRASH_DUMP
-		/*
-		 * If we are doing a crash dump, we still need to know
-		 * the real memory size before the original memory map is
-		 * reset.
-		 */
-		saved_max_pfn = e820__end_of_ram_pfn();
-#endif
 		e820_table->nr_entries = 0;
 		userdef = 1;
 		return 0;
diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index 4664fc1871de..bc156285d097 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -97,8 +97,6 @@ extern void unregister_oldmem_pfn_is_ram(void);
 static inline bool is_kdump_kernel(void) { return 0; }
 #endif /* CONFIG_CRASH_DUMP */
 
-extern unsigned long saved_max_pfn;
-
 /* Device Dump information to be filled by drivers */
 struct vmcoredd_data {
 	char dump_name[VMCOREDD_MAX_NAME_BYTES]; /* Unique name of the dump */
diff --git a/kernel/crash_dump.c b/kernel/crash_dump.c
index 9c23ae074b40..92da32275af5 100644
--- a/kernel/crash_dump.c
+++ b/kernel/crash_dump.c
@@ -5,12 +5,6 @@
 #include <linux/errno.h>
 #include <linux/export.h>
 
-/*
- * If we have booted due to a crash, max_pfn will be a very low value. We need
- * to know the amount of memory that the previous kernel used.
- */
-unsigned long saved_max_pfn;
-
 /*
  * stores the physical address of elf header of crash image
  *
-- 
2.25.1