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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Dave Young <dyoung@redhat.com>
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Date: Mon, 4 Jun 2018 01:38:25 -0400
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Subject: [PATCH] kdump: round up the total memory size to 128M for crashkernel
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reservation
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Message-id: <20180604013831.523644967@redhat.com>
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Patchwork-id: 8165
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O-Subject: [kernel team] [PATCH RHEL8.0 V2 1/2] kdump: round up the total memory size to 128M for crashkernel reservation
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Bugzilla: 1507353
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RH-Acked-by: Don Zickus <dzickus@redhat.com>
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RH-Acked-by: Baoquan He <bhe@redhat.com>
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RH-Acked-by: Pingfan Liu <piliu@redhat.com>
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1507353
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Build: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=16534135
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Tested: ppc64le, x86_64 with several memory sizes.
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The total memory size we get in kernel is usually slightly less than 2G with
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2G memory module machine. The main reason is bios/firmware reserve some area
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it will not export all memory as usable to Linux.
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2G memory X86 kvm guest test result of the total_mem value:
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UEFI boot with ovmf: 0x7ef10000
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Legacy boot kvm guest: 0x7ff7cc00
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This is also a problem on arm64 UEFI booted system according to my test.
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Thus for example crashkernel=1G-2G:128M, if we have a 1G memory
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machine, we get total size 1023M from firmware then it will not fall
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into 1G-2G thus no memory reserved. User will never know that, it is
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hard to let user to know the exact total value we get in kernel
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An option is to use dmi/smbios to get physical memory size, but it's not
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reliable as well. According to Prarit hardware vendors sometimes screw this up.
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Thus round up total size to 128M to workaround this problem.
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Posted below patch in upstream, but no response yet:
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http://lists.infradead.org/pipermail/kexec/2018-April/020568.html
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Upstream Status: RHEL only
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Signed-off-by: Dave Young <dyoung@redhat.com>
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Signed-off-by: Herton R. Krzesinski <herton@redhat.com>
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---
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kernel/crash_core.c | 14 ++++++++++++--
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1 file changed, 12 insertions(+), 2 deletions(-)
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diff --git a/kernel/crash_core.c b/kernel/crash_core.c
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index 9f1557b98468..d631d22089ba 100644
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--- a/kernel/crash_core.c
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+++ b/kernel/crash_core.c
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@@ -7,6 +7,7 @@
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#include <linux/crash_core.h>
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#include <linux/utsname.h>
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#include <linux/vmalloc.h>
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+#include <linux/sizes.h>
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#include <asm/page.h>
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#include <asm/sections.h>
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@@ -39,6 +40,15 @@ static int __init parse_crashkernel_mem(char *cmdline,
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unsigned long long *crash_base)
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{
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char *cur = cmdline, *tmp;
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+ unsigned long long total_mem = system_ram;
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+
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+ /*
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+ * Firmware sometimes reserves some memory regions for it's own use.
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+ * so we get less than actual system memory size.
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+ * Workaround this by round up the total size to 128M which is
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+ * enough for most test cases.
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+ */
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+ total_mem = roundup(total_mem, SZ_128M);
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/* for each entry of the comma-separated list */
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do {
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@@ -83,13 +93,13 @@ static int __init parse_crashkernel_mem(char *cmdline,
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return -EINVAL;
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}
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cur = tmp;
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- if (size >= system_ram) {
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+ if (size >= total_mem) {
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pr_warn("crashkernel: invalid size\n");
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return -EINVAL;
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}
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/* match ? */
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- if (system_ram >= start && system_ram < end) {
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+ if (total_mem >= start && total_mem < end) {
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*crash_size = size;
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break;
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}
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--
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2.26.2
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