Re: [PATCH v2 2/3] vmcore: allow fadump to export vmcore even if is_kdump_kernel() is false

[Hari Bathini]

On 11/09/23 4:01 pm, Baoquan He wrote:

On 09/11/23 at 05:13pm, Michael Ellerman wrote:

Hari Bathini <hbath...@linux.ibm.com> writes:

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.

...

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;
  }

I think it would be cleaner to decouple is_vmcore_usable() and
vmcore_usable() from is_kdump_kernel().

ie, make them operate solely based on the value of elforehdr_addr:

static inline int is_vmcore_usable(void)
{
        elfcorehdr_addr != ELFCORE_ADDR_ERR && \
                elfcorehdr_addr != ELFCORE_ADDR_MAX;

Agree. I fell into the blind corner of thinking earlier. Above change
is better.

Thanks for the reviews.
Posted v3.

- Hari

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