From ee97347fe058d02035f354d59a5aa5aa6e1be4cc Mon Sep 17 00:00:00 2001
From: Hari Bathini <hbathini@linux.ibm.com>
Date: Tue, 22 Mar 2022 14:46:17 -0700
Subject: [PATCH] powerpc/fadump: opt out from freeing pages on cma activation
failure
References: bsc#1195099 ltc#196102
Patch-mainline: v5.18-rc1
Git-commit: ee97347fe058d02035f354d59a5aa5aa6e1be4cc
With commit a4e92ce8e4c8 ("powerpc/fadump: Reservationless firmware
assisted dump"), Linux kernel's Contiguous Memory Allocator (CMA) based
reservation was introduced in fadump. That change was aimed at using CMA
to let applications utilize the memory reserved for fadump while blocking
it from being used for kernel pages. The assumption was, even if CMA
activation fails for whatever reason, the memory still remains reserved to
avoid it from being used for kernel pages. But commit 072355c1cf2d
("mm/cma: expose all pages to the buddy if activation of an area fails")
breaks this assumption as it started exposing all pages to buddy allocator
on CMA activation failure. It led to warning messages like below while
running crash-utility on vmcore of a kernel having above two commits:
crash: seek error: kernel virtual address: <from reserved region>
To fix this problem, opt out from exposing pages to buddy allocator on CMA
activation failure for fadump reserved memory.
Link: https://lkml.kernel.org/r/20220117075246.36072-3-hbathini@linux.ibm.com
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/kernel/fadump.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 7eb67201ea41..4fdb7c77fda1 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -112,6 +112,12 @@ static int __init fadump_cma_init(void)
return 1;
}
+ /*
+ * If CMA activation fails, keep the pages reserved, instead of
+ * exposing them to buddy allocator. Same as 'fadump=nocma' case.
+ */
+ cma_reserve_pages_on_error(fadump_cma);
+
/*
* So we now have successfully initialized cma area for fadump.
*/
--
2.34.1