[PATCH v3 1/2] vmcore: remove dependency with is_kdump_kernel() for exporting vmcore

[PATCH v3 1/2] vmcore: remove dependency with is_kdump_kernel() for exporting vmcore

[Hari Bathini]

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 may not be desirable
for fadump, allow is_kdump_kernel() to be defined differently for such
scenarios. With this, is_kdump_kernel() could be false while vmcore is
usable. So, remove unnecessary dependency with is_kdump_kernel(), for
exporting vmcore.

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

Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---

Changes in v3:
* Decoupled is_vmcore_usable() & vmcore_unusable() from is_kdump_kernel()
  as suggested here: 
    https://lore.kernel.org/linuxppc-dev/ZP7si3UMVpPfYV+w@MiWiFi-R3L-srv/T/#m13ae5a7e4ba6f4d8397f0f66581832292eee3a85


 include/linux/crash_dump.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index 0f3a656293b0..acc55626afdc 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 +65,7 @@ static inline bool is_kdump_kernel(void)
 {
 	return elfcorehdr_addr != ELFCORE_ADDR_MAX;
 }
+#endif
 
 /* is_vmcore_usable() checks if the kernel is booting after a panic and
  * the vmcore region is usable.
@@ -75,7 +77,8 @@ 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 elfcorehdr_addr != ELFCORE_ADDR_ERR &&
+		elfcorehdr_addr != ELFCORE_ADDR_MAX ? 1 : 0;
 }
 
 /* vmcore_unusable() marks the vmcore as unusable,
@@ -84,8 +87,7 @@ static inline int is_vmcore_usable(void)
 
 static inline void vmcore_unusable(void)
 {
-	if (is_kdump_kernel())
-		elfcorehdr_addr = ELFCORE_ADDR_ERR;
+	elfcorehdr_addr = ELFCORE_ADDR_ERR;
 }
 
 /**
-- 
2.41.0

[PATCH v3 2/2] powerpc/fadump: make is_kdump_kernel() return false when fadump is active

[Hari Bathini]

Currently, is_kdump_kernel() returns true in crash dump capture kernel
for both kdump and fadump crash dump capturing methods, as both these
methods set elfcorehdr_addr. Some restrictions enforced for crash dump
capture kernel, based on is_kdump_kernel(), are specifically meant for
kdump case and not desirable for fadump - eg. IO queues restriction in
device drivers. So, define is_kdump_kernel() to return false when f/w
assisted dump is active.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---
 arch/powerpc/include/asm/kexec.h |  8 ++++++--
 arch/powerpc/kernel/crash_dump.c | 12 ++++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index a1ddba01e7d1..e1b43aa12175 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -99,10 +99,14 @@ void relocate_new_kernel(unsigned long indirection_page, unsigned long reboot_co
 
 void kexec_copy_flush(struct kimage *image);
 
-#if defined(CONFIG_CRASH_DUMP) && defined(CONFIG_PPC_RTAS)
+#if defined(CONFIG_CRASH_DUMP)
+bool is_kdump_kernel(void);
+#define is_kdump_kernel			is_kdump_kernel
+#if defined(CONFIG_PPC_RTAS)
 void crash_free_reserved_phys_range(unsigned long begin, unsigned long end);
 #define crash_free_reserved_phys_range crash_free_reserved_phys_range
-#endif
+#endif /* CONFIG_PPC_RTAS */
+#endif /* CONFIG_CRASH_DUMP */
 
 #ifdef CONFIG_KEXEC_FILE
 extern const struct kexec_file_ops kexec_elf64_ops;
diff --git a/arch/powerpc/kernel/crash_dump.c b/arch/powerpc/kernel/crash_dump.c
index 9a3b85bfc83f..2086fa6cdc25 100644
--- a/arch/powerpc/kernel/crash_dump.c
+++ b/arch/powerpc/kernel/crash_dump.c
@@ -19,6 +19,7 @@
 #include <linux/uio.h>
 #include <asm/rtas.h>
 #include <asm/inst.h>
+#include <asm/fadump.h>
 
 #ifdef DEBUG
 #include <asm/udbg.h>
@@ -92,6 +93,17 @@ ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
 	return csize;
 }
 
+/*
+ * Return true only when kexec based kernel dump capturing method is used.
+ * This ensures all restritions applied for kdump case are not automatically
+ * applied for fadump case.
+ */
+bool is_kdump_kernel(void)
+{
+	return !is_fadump_active() && elfcorehdr_addr != ELFCORE_ADDR_MAX;
+}
+EXPORT_SYMBOL_GPL(is_kdump_kernel);
+
 #ifdef CONFIG_PPC_RTAS
 /*
  * The crashkernel region will almost always overlap the RTAS region, so
-- 
2.41.0

Re: [PATCH v3 2/2] powerpc/fadump: make is_kdump_kernel() return false when fadump is active

[Baoquan He]

On 09/12/23 at 01:59pm, Hari Bathini wrote:
> Currently, is_kdump_kernel() returns true in crash dump capture kernel
> for both kdump and fadump crash dump capturing methods, as both these
> methods set elfcorehdr_addr. Some restrictions enforced for crash dump
> capture kernel, based on is_kdump_kernel(), are specifically meant for
> kdump case and not desirable for fadump - eg. IO queues restriction in
> device drivers. So, define is_kdump_kernel() to return false when f/w
> assisted dump is active.
> 
> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
> ---
>  arch/powerpc/include/asm/kexec.h |  8 ++++++--
>  arch/powerpc/kernel/crash_dump.c | 12 ++++++++++++
>  2 files changed, 18 insertions(+), 2 deletions(-)

LGTM,

Acked-by: Baoquan He <bhe@redhat.com>

> 
> diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
> index a1ddba01e7d1..e1b43aa12175 100644
> --- a/arch/powerpc/include/asm/kexec.h
> +++ b/arch/powerpc/include/asm/kexec.h
> @@ -99,10 +99,14 @@ void relocate_new_kernel(unsigned long indirection_page, unsigned long reboot_co
>  
>  void kexec_copy_flush(struct kimage *image);
>  
> -#if defined(CONFIG_CRASH_DUMP) && defined(CONFIG_PPC_RTAS)
> +#if defined(CONFIG_CRASH_DUMP)
> +bool is_kdump_kernel(void);
> +#define is_kdump_kernel			is_kdump_kernel
> +#if defined(CONFIG_PPC_RTAS)
>  void crash_free_reserved_phys_range(unsigned long begin, unsigned long end);
>  #define crash_free_reserved_phys_range crash_free_reserved_phys_range
> -#endif
> +#endif /* CONFIG_PPC_RTAS */
> +#endif /* CONFIG_CRASH_DUMP */
>  
>  #ifdef CONFIG_KEXEC_FILE
>  extern const struct kexec_file_ops kexec_elf64_ops;
> diff --git a/arch/powerpc/kernel/crash_dump.c b/arch/powerpc/kernel/crash_dump.c
> index 9a3b85bfc83f..2086fa6cdc25 100644
> --- a/arch/powerpc/kernel/crash_dump.c
> +++ b/arch/powerpc/kernel/crash_dump.c
> @@ -19,6 +19,7 @@
>  #include <linux/uio.h>
>  #include <asm/rtas.h>
>  #include <asm/inst.h>
> +#include <asm/fadump.h>
>  
>  #ifdef DEBUG
>  #include <asm/udbg.h>
> @@ -92,6 +93,17 @@ ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
>  	return csize;
>  }
>  
> +/*
> + * Return true only when kexec based kernel dump capturing method is used.
> + * This ensures all restritions applied for kdump case are not automatically
> + * applied for fadump case.
> + */
> +bool is_kdump_kernel(void)
> +{
> +	return !is_fadump_active() && elfcorehdr_addr != ELFCORE_ADDR_MAX;
> +}
> +EXPORT_SYMBOL_GPL(is_kdump_kernel);
> +
>  #ifdef CONFIG_PPC_RTAS
>  /*
>   * The crashkernel region will almost always overlap the RTAS region, so
> -- 
> 2.41.0
> 

Re: [PATCH v3 1/2] vmcore: remove dependency with is_kdump_kernel() for exporting vmcore

[Baoquan He]

On 09/12/23 at 01:59pm, Hari Bathini wrote:
> 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 may not be desirable
> for fadump, allow is_kdump_kernel() to be defined differently for such
> scenarios. With this, is_kdump_kernel() could be false while vmcore is
> usable. So, remove unnecessary dependency with is_kdump_kernel(), for
> exporting vmcore.
> 
> [1] https://docs.kernel.org/powerpc/firmware-assisted-dump.html
> 
> Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
> ---
> 
> Changes in v3:
> * Decoupled is_vmcore_usable() & vmcore_unusable() from is_kdump_kernel()
>   as suggested here: 
>     https://lore.kernel.org/linuxppc-dev/ZP7si3UMVpPfYV+w@MiWiFi-R3L-srv/T/#m13ae5a7e4ba6f4d8397f0f66581832292eee3a85
> 
> 
>  include/linux/crash_dump.h | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)

LGTM,

Acked-by: Baoquan He <bhe@redhat.com>

> 
> diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
> index 0f3a656293b0..acc55626afdc 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 +65,7 @@ static inline bool is_kdump_kernel(void)
>  {
>  	return elfcorehdr_addr != ELFCORE_ADDR_MAX;
>  }
> +#endif
>  
>  /* is_vmcore_usable() checks if the kernel is booting after a panic and
>   * the vmcore region is usable.
> @@ -75,7 +77,8 @@ 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 elfcorehdr_addr != ELFCORE_ADDR_ERR &&
> +		elfcorehdr_addr != ELFCORE_ADDR_MAX ? 1 : 0;
>  }
>  
>  /* vmcore_unusable() marks the vmcore as unusable,
> @@ -84,8 +87,7 @@ static inline int is_vmcore_usable(void)
>  
>  static inline void vmcore_unusable(void)
>  {
> -	if (is_kdump_kernel())
> -		elfcorehdr_addr = ELFCORE_ADDR_ERR;
> +	elfcorehdr_addr = ELFCORE_ADDR_ERR;
>  }
>  
>  /**
> -- 
> 2.41.0
> 

Re: [PATCH v3 1/2] vmcore: remove dependency with is_kdump_kernel() for exporting vmcore

[Michael Ellerman]

On Tue, 12 Sep 2023 13:59:49 +0530, Hari Bathini wrote:
> 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 may not be desirable
> for fadump, allow is_kdump_kernel() to be defined differently for such
> scenarios. With this, is_kdump_kernel() could be false while vmcore is
> usable. So, remove unnecessary dependency with is_kdump_kernel(), for
> exporting vmcore.
> 
> [...]

Applied to powerpc/next.

[1/2] vmcore: remove dependency with is_kdump_kernel() for exporting vmcore
      https://git.kernel.org/powerpc/c/86328b338c3996b814417dd68e3f899a1a649059
[2/2] powerpc/fadump: make is_kdump_kernel() return false when fadump is active
      https://git.kernel.org/powerpc/c/b098f1c32365304633077d73e4ae21c72d4241b3

cheers