linux-kernel - [PATCH v2 2/3] vmcore: allow fadump to export vmcore even if is_kdump

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Message-ID: <20230905183604.568996-2-hbathini@linux.ibm.com>
Date:   Wed,  6 Sep 2023 00:06:03 +0530
From:   Hari Bathini <hbathini@...ux.ibm.com>
To:     lkml <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Kexec-ml <kexec@...ts.infradead.org>
Cc:     Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        Sourabh Jain <sourabhjain@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH v2 2/3] vmcore: allow fadump to export vmcore even if is_kdump_kernel() is false

Currently, is_kdump_kernel() returns true when elfcorehdr_addr is set.
While elfcorehdr_addr is set for kexec based kernel dump mechanism,
alternate dump capturing methods like fadump [1] also set it to export
the vmcore. Since, is_kdump_kernel() is used to restrict resources in
crash dump capture kernel and such restrictions are not desirable for
fadump, allow is_kdump_kernel() to be defined differently for fadump
case. With that change, include is_fadump_active() check in functions
is_vmcore_usable() & vmcore_unusable() to be able to export vmcore for
fadump case too.

[1] https://docs.kernel.org/powerpc/firmware-assisted-dump.html

Signed-off-by: Hari Bathini <hbathini@...ux.ibm.com>
---

Changes in v2:
* is_fadump_active() check added to is_vmcore_usable() as suggested
  by Baoquan.


 include/linux/crash_dump.h | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index 0f3a656293b0..de8a9fabfb6f 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -50,6 +50,7 @@ void vmcore_cleanup(void);
 #define vmcore_elf64_check_arch(x) (elf_check_arch(x) || vmcore_elf_check_arch_cross(x))
 #endif
 
+#ifndef is_kdump_kernel
 /*
  * is_kdump_kernel() checks whether this kernel is booting after a panic of
  * previous kernel or not. This is determined by checking if previous kernel
@@ -64,6 +65,19 @@ static inline bool is_kdump_kernel(void)
 {
 	return elfcorehdr_addr != ELFCORE_ADDR_MAX;
 }
+#endif
+
+#ifndef is_fadump_active
+/*
+ * If f/w assisted dump capturing mechanism (fadump), instead of kexec based
+ * dump capturing mechanism (kdump) is exporting the vmcore, then this function
+ * will be defined in arch specific code to return true, when appropriate.
+ */
+static inline bool is_fadump_active(void)
+{
+	return false;
+}
+#endif
 
 /* is_vmcore_usable() checks if the kernel is booting after a panic and
  * the vmcore region is usable.
@@ -75,7 +89,8 @@ static inline bool is_kdump_kernel(void)
 
 static inline int is_vmcore_usable(void)
 {
-	return is_kdump_kernel() && elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0;
+	return (is_kdump_kernel() || is_fadump_active())
+		&& elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0;
 }
 
 /* vmcore_unusable() marks the vmcore as unusable,
@@ -84,7 +99,7 @@ static inline int is_vmcore_usable(void)
 
 static inline void vmcore_unusable(void)
 {
-	if (is_kdump_kernel())
+	if (is_kdump_kernel() || is_fadump_active())
 		elfcorehdr_addr = ELFCORE_ADDR_ERR;
 }
 
-- 
2.41.0