[PATCH] x86/mm: Fix phys_to_target_node() export

[PATCH] x86/mm: Fix phys_to_target_node() export

[Dan Williams]

The core-mm has a default __weak implementation of phys_to_target_node()
when the architecture does not override it. That symbol is exported
for modules. However, while the export in mm/memory_hotplug.c exported
the symbol in the configuration cases of:

	CONFIG_NUMA_KEEP_MEMINFO=y
	CONFIG_MEMORY_HOTPLUG=y

...and:

	CONFIG_NUMA_KEEP_MEMINFO=n
	CONFIG_MEMORY_HOTPLUG=y

...it failed to export the symbol in the case of:

	CONFIG_NUMA_KEEP_MEMINFO=y
	CONFIG_MEMORY_HOTPLUG=n

Always export the symbol from the CONFIG_NUMA_KEEP_MEMINFO section of
arch/x86/mm/numa.c, and teach mm/memory_hotplug.c to optionally export
in case arch/x86/mm/numa.c has already performed the export.

The dependency on NUMA_KEEP_MEMINFO for DEV_DAX_HMEM_DEVICES is invalid
now that the symbol is properly exported in all combinations of
CONFIG_NUMA_KEEP_MEMINFO and CONFIG_MEMORY_HOTPLUG. Note that in the
CONFIG_NUMA=n case no export is needed since their is a dummy static
inline implementation of phys_to_target_node() in that case.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Reported-by: kernel test robot <lkp@intel.com>
Fixes: a035b6bf863e ("mm/memory_hotplug: introduce default phys_to_target_node() implementation")
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: x86@kernel.org
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 arch/x86/mm/numa.c  |    1 +
 drivers/dax/Kconfig |    1 -
 mm/memory_hotplug.c |    5 +++++
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index 44148691d78b..e025947f19e0 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -938,6 +938,7 @@ int phys_to_target_node(phys_addr_t start)
 
 	return meminfo_to_nid(&numa_reserved_meminfo, start);
 }
+EXPORT_SYMBOL_GPL(phys_to_target_node);
 
 int memory_add_physaddr_to_nid(u64 start)
 {
diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index 567428e10b7b..d2834c2cfa10 100644
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -50,7 +50,6 @@ config DEV_DAX_HMEM
 	  Say M if unsure.
 
 config DEV_DAX_HMEM_DEVICES
-	depends on NUMA_KEEP_MEMINFO # for phys_to_target_node()
 	depends on DEV_DAX_HMEM && DAX=y
 	def_bool y
 
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index b44d4c7ba73b..ed326b489674 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -365,9 +365,14 @@ int __weak phys_to_target_node(u64 start)
 			start);
 	return 0;
 }
+
+/* If the arch did not export a strong symbol, export the weak one. */
+#ifndef CONFIG_NUMA_KEEP_MEMINFO
 EXPORT_SYMBOL_GPL(phys_to_target_node);
 #endif
 
+#endif
+
 /* find the smallest valid pfn in the range [start_pfn, end_pfn) */
 static unsigned long find_smallest_section_pfn(int nid, struct zone *zone,
 				     unsigned long start_pfn,
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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Randy Dunlap]

On 10/29/20 7:29 PM, Dan Williams wrote:
> The core-mm has a default __weak implementation of phys_to_target_node()
> when the architecture does not override it. That symbol is exported
> for modules. However, while the export in mm/memory_hotplug.c exported
> the symbol in the configuration cases of:
> 
> 	CONFIG_NUMA_KEEP_MEMINFO=y
> 	CONFIG_MEMORY_HOTPLUG=y
> 
> ...and:
> 
> 	CONFIG_NUMA_KEEP_MEMINFO=n
> 	CONFIG_MEMORY_HOTPLUG=y
> 
> ...it failed to export the symbol in the case of:
> 
> 	CONFIG_NUMA_KEEP_MEMINFO=y
> 	CONFIG_MEMORY_HOTPLUG=n
> 
> Always export the symbol from the CONFIG_NUMA_KEEP_MEMINFO section of
> arch/x86/mm/numa.c, and teach mm/memory_hotplug.c to optionally export
> in case arch/x86/mm/numa.c has already performed the export.
> 
> The dependency on NUMA_KEEP_MEMINFO for DEV_DAX_HMEM_DEVICES is invalid
> now that the symbol is properly exported in all combinations of
> CONFIG_NUMA_KEEP_MEMINFO and CONFIG_MEMORY_HOTPLUG. Note that in the
> CONFIG_NUMA=n case no export is needed since their is a dummy static
> inline implementation of phys_to_target_node() in that case.
> 
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Reported-by: Thomas Gleixner <tglx@linutronix.de>
> Reported-by: kernel test robot <lkp@intel.com>
> Fixes: a035b6bf863e ("mm/memory_hotplug: introduce default phys_to_target_node() implementation")
> Cc: Joao Martins <joao.m.martins@oracle.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: x86@kernel.org
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Looks good. Thanks.

Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested


> ---
>  arch/x86/mm/numa.c  |    1 +
>  drivers/dax/Kconfig |    1 -
>  mm/memory_hotplug.c |    5 +++++
>  3 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> index 44148691d78b..e025947f19e0 100644
> --- a/arch/x86/mm/numa.c
> +++ b/arch/x86/mm/numa.c
> @@ -938,6 +938,7 @@ int phys_to_target_node(phys_addr_t start)
>  
>  	return meminfo_to_nid(&numa_reserved_meminfo, start);
>  }
> +EXPORT_SYMBOL_GPL(phys_to_target_node);
>  
>  int memory_add_physaddr_to_nid(u64 start)
>  {
> diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
> index 567428e10b7b..d2834c2cfa10 100644
> --- a/drivers/dax/Kconfig
> +++ b/drivers/dax/Kconfig
> @@ -50,7 +50,6 @@ config DEV_DAX_HMEM
>  	  Say M if unsure.
>  
>  config DEV_DAX_HMEM_DEVICES
> -	depends on NUMA_KEEP_MEMINFO # for phys_to_target_node()
>  	depends on DEV_DAX_HMEM && DAX=y
>  	def_bool y
>  
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index b44d4c7ba73b..ed326b489674 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -365,9 +365,14 @@ int __weak phys_to_target_node(u64 start)
>  			start);
>  	return 0;
>  }
> +
> +/* If the arch did not export a strong symbol, export the weak one. */
> +#ifndef CONFIG_NUMA_KEEP_MEMINFO
>  EXPORT_SYMBOL_GPL(phys_to_target_node);
>  #endif
>  
> +#endif
> +
>  /* find the smallest valid pfn in the range [start_pfn, end_pfn) */
>  static unsigned long find_smallest_section_pfn(int nid, struct zone *zone,
>  				     unsigned long start_pfn,
> 
> 


-- 
~Randy
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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[David Hildenbrand]

On 30.10.20 03:29, Dan Williams wrote:
> The core-mm has a default __weak implementation of phys_to_target_node()
> when the architecture does not override it. That symbol is exported
> for modules. However, while the export in mm/memory_hotplug.c exported
> the symbol in the configuration cases of:
> 
> 	CONFIG_NUMA_KEEP_MEMINFO=y
> 	CONFIG_MEMORY_HOTPLUG=y
> 
> ...and:
> 
> 	CONFIG_NUMA_KEEP_MEMINFO=n
> 	CONFIG_MEMORY_HOTPLUG=y
> 
> ...it failed to export the symbol in the case of:
> 
> 	CONFIG_NUMA_KEEP_MEMINFO=y
> 	CONFIG_MEMORY_HOTPLUG=n
> 
> Always export the symbol from the CONFIG_NUMA_KEEP_MEMINFO section of
> arch/x86/mm/numa.c, and teach mm/memory_hotplug.c to optionally export
> in case arch/x86/mm/numa.c has already performed the export.
> 
> The dependency on NUMA_KEEP_MEMINFO for DEV_DAX_HMEM_DEVICES is invalid
> now that the symbol is properly exported in all combinations of
> CONFIG_NUMA_KEEP_MEMINFO and CONFIG_MEMORY_HOTPLUG. Note that in the
> CONFIG_NUMA=n case no export is needed since their is a dummy static
> inline implementation of phys_to_target_node() in that case.
> 
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Reported-by: Thomas Gleixner <tglx@linutronix.de>
> Reported-by: kernel test robot <lkp@intel.com>
> Fixes: a035b6bf863e ("mm/memory_hotplug: introduce default phys_to_target_node() implementation")
> Cc: Joao Martins <joao.m.martins@oracle.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: x86@kernel.org
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>   arch/x86/mm/numa.c  |    1 +
>   drivers/dax/Kconfig |    1 -
>   mm/memory_hotplug.c |    5 +++++
>   3 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> index 44148691d78b..e025947f19e0 100644
> --- a/arch/x86/mm/numa.c
> +++ b/arch/x86/mm/numa.c
> @@ -938,6 +938,7 @@ int phys_to_target_node(phys_addr_t start)
>   
>   	return meminfo_to_nid(&numa_reserved_meminfo, start);
>   }
> +EXPORT_SYMBOL_GPL(phys_to_target_node);
>   
>   int memory_add_physaddr_to_nid(u64 start)
>   {
> diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
> index 567428e10b7b..d2834c2cfa10 100644
> --- a/drivers/dax/Kconfig
> +++ b/drivers/dax/Kconfig
> @@ -50,7 +50,6 @@ config DEV_DAX_HMEM
>   	  Say M if unsure.
>   
>   config DEV_DAX_HMEM_DEVICES
> -	depends on NUMA_KEEP_MEMINFO # for phys_to_target_node()
>   	depends on DEV_DAX_HMEM && DAX=y
>   	def_bool y
>   
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index b44d4c7ba73b..ed326b489674 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -365,9 +365,14 @@ int __weak phys_to_target_node(u64 start)
>   			start);
>   	return 0;
>   }
> +
> +/* If the arch did not export a strong symbol, export the weak one. */
> +#ifndef CONFIG_NUMA_KEEP_MEMINFO
>   EXPORT_SYMBOL_GPL(phys_to_target_node);
>   #endif
>   
> +#endif
> +
>   /* find the smallest valid pfn in the range [start_pfn, end_pfn) */
>   static unsigned long find_smallest_section_pfn(int nid, struct zone *zone,
>   				     unsigned long start_pfn,
> 
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb
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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Dan Williams]

On Thu, Oct 29, 2020 at 7:29 PM Dan Williams <dan.j.williams@intel.com> wrote:
>
> The core-mm has a default __weak implementation of phys_to_target_node()
> when the architecture does not override it. That symbol is exported
> for modules. However, while the export in mm/memory_hotplug.c exported
> the symbol in the configuration cases of:
>
>         CONFIG_NUMA_KEEP_MEMINFO=y
>         CONFIG_MEMORY_HOTPLUG=y
>
> ...and:
>
>         CONFIG_NUMA_KEEP_MEMINFO=n
>         CONFIG_MEMORY_HOTPLUG=y
>
> ...it failed to export the symbol in the case of:
>
>         CONFIG_NUMA_KEEP_MEMINFO=y
>         CONFIG_MEMORY_HOTPLUG=n
>
> Always export the symbol from the CONFIG_NUMA_KEEP_MEMINFO section of
> arch/x86/mm/numa.c, and teach mm/memory_hotplug.c to optionally export
> in case arch/x86/mm/numa.c has already performed the export.
>
> The dependency on NUMA_KEEP_MEMINFO for DEV_DAX_HMEM_DEVICES is invalid
> now that the symbol is properly exported in all combinations of
> CONFIG_NUMA_KEEP_MEMINFO and CONFIG_MEMORY_HOTPLUG. Note that in the
> CONFIG_NUMA=n case no export is needed since their is a dummy static
> inline implementation of phys_to_target_node() in that case.
>
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Reported-by: Thomas Gleixner <tglx@linutronix.de>
> Reported-by: kernel test robot <lkp@intel.com>
> Fixes: a035b6bf863e ("mm/memory_hotplug: introduce default phys_to_target_node() implementation")
> Cc: Joao Martins <joao.m.martins@oracle.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: x86@kernel.org
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Thomas, do you want to ack this so Andrew can pick it up, or I can
take it through as a device-dax update, but either way the diffstat
warrants x86 + mm acks.
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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Thomas Gleixner]

On Fri, Oct 30 2020 at 18:54, Dan Williams wrote:
> Thomas, do you want to ack this so Andrew can pick it up, or I can
> take it through as a device-dax update, but either way the diffstat
> warrants x86 + mm acks.

It's butt ugly but I couldn't come up with anything better right
away. So, FWIW:

Acked-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Thomas Gleixner <tglx@linutronix.de>
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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Dan Williams]

On Fri, Oct 30, 2020 at 8:02 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Fri, Oct 30 2020 at 18:54, Dan Williams wrote:
> > Thomas, do you want to ack this so Andrew can pick it up, or I can
> > take it through as a device-dax update, but either way the diffstat
> > warrants x86 + mm acks.
>
> It's butt ugly but I couldn't come up with anything better right
> away. So, FWIW:
>
> Acked-by: Thomas Gleixner <tglx@linutronix.de>
> Tested-by: Thomas Gleixner <tglx@linutronix.de>

Almost-threw-up-in-my-mouth-a-little-bit-by?
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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Christoph Hellwig]

On Thu, Oct 29, 2020 at 07:29:45PM -0700, Dan Williams wrote:
> The core-mm has a default __weak implementation of phys_to_target_node()
> when the architecture does not override it. That symbol is exported
> for modules. However, while the export in mm/memory_hotplug.c exported
> the symbol in the configuration cases of:

Which just means that we should never export weak symbols.  So instead
of hacking around this introduce a symbol that indicates that the
architecture impements phys_to_target_node, and don't defined it at all
in common code for that case.

> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -365,9 +365,14 @@ int __weak phys_to_target_node(u64 start)
>  			start);
>  	return 0;
>  }
> +
> +/* If the arch did not export a strong symbol, export the weak one. */
> +#ifndef CONFIG_NUMA_KEEP_MEMINFO
>  EXPORT_SYMBOL_GPL(phys_to_target_node);
>  #endif
>  
> +#endif

i.e. move the ifdef to include the actual phys_to_target_node
definition, and remove the __weak from it here.
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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Dan Williams]

[-- Attachment #1: Type: text/plain, Size: 1922 bytes --]

On Sat, Oct 31, 2020 at 2:10 AM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Thu, Oct 29, 2020 at 07:29:45PM -0700, Dan Williams wrote:
> > The core-mm has a default __weak implementation of phys_to_target_node()
> > when the architecture does not override it. That symbol is exported
> > for modules. However, while the export in mm/memory_hotplug.c exported
> > the symbol in the configuration cases of:
>
> Which just means that we should never export weak symbols.  So instead
> of hacking around this introduce a symbol that indicates that the
> architecture impements phys_to_target_node, and don't defined it at all
> in common code for that case.

So I agree with this, but it made me realize that the way
memory_add_physaddr_to_nid() was defined as an exported weak symbol is
similarly broken.

> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -365,9 +365,14 @@ int __weak phys_to_target_node(u64 start)
> >                       start);
> >       return 0;
> >  }
> > +
> > +/* If the arch did not export a strong symbol, export the weak one. */
> > +#ifndef CONFIG_NUMA_KEEP_MEMINFO
> >  EXPORT_SYMBOL_GPL(phys_to_target_node);
> >  #endif
> >
> > +#endif
>
> i.e. move the ifdef to include the actual phys_to_target_node
> definition, and remove the __weak from it here.

The trick is finding an arch common way to pick up the presence of the
phys_to_target_node() override, and it still has the wart of ifdefery
in C code.

I went a bit deeper and moved all the fallback routines to
linux/numa.h and the overrides in all archs that care to
asm/sparsemem.h. Note that asm/sparsemem.h was not my first choice,
but it happened to be where powerpc was already defining its
phys-addr-to-node-id infrastructure, and my first choice header,
asm/numa.h, is not universally available.

The attached patch is going through some kbuild-robot exposure to make
sure I did not break anything else.

[-- Attachment #2: 0001-x86-mm-Fix-phys_to_target_node-export.patch --]
[-- Type: text/x-patch, Size: 8531 bytes --]

From ec0a0ca84fc4ba64dadc86146d2ac42379a686ff Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Thu, 29 Oct 2020 19:14:07 -0700
Subject: [PATCH] x86/mm: Fix phys_to_target_node() export

The core-mm has a default __weak implementation of phys_to_target_node()
to mirror the weak definition of memory_add_physaddr_to_nid(). That
symbol is exported for modules. However, while the export in
mm/memory_hotplug.c exported the symbol in the configuration cases of:

	CONFIG_NUMA_KEEP_MEMINFO=y
	CONFIG_MEMORY_HOTPLUG=y

...and:

	CONFIG_NUMA_KEEP_MEMINFO=n
	CONFIG_MEMORY_HOTPLUG=y

...it failed to export the symbol in the case of:

	CONFIG_NUMA_KEEP_MEMINFO=y
	CONFIG_MEMORY_HOTPLUG=n

Not only is that broken, but Christoph points out that the kernel should
not be exporting any __weak symbol, which means that
memory_add_physaddr_to_nid() example that phys_to_target_node() copied
is broken too.

Rework the definition of phys_to_target_node() and
memory_add_physaddr_to_nid() to not require weak symbols. Move to the
common arch override design-pattern of an asm header defining a symbol
to replace the default implementation.

The only common header that all memory_add_physaddr_to_nid() producing
architectures implement is asm/sparsemem.h. In fact, powerpc already
defines its memory_add_physaddr_to_nid() helper in sparsemem.h.
Double-down on that observation and define phys_to_target_node() where
necessary in asm/sparsemem.h. An alternate consideration that was
discarded was to put this override in asm/numa.h, but that entangles
with the definition of MAX_NUMNODES relative to the inclusion of
linux/nodemask.h, and requires powerpc to grow a new header.

The dependency on NUMA_KEEP_MEMINFO for DEV_DAX_HMEM_DEVICES is invalid
now that the symbol is properly exported / stubbed in all combinations
of CONFIG_NUMA_KEEP_MEMINFO and CONFIG_MEMORY_HOTPLUG.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Christoph Hellwig <hch@infradead.org>
Fixes: a035b6bf863e ("mm/memory_hotplug: introduce default phys_to_target_node() implementation")
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: x86@kernel.org
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 arch/ia64/include/asm/sparsemem.h    |  4 ++++
 arch/powerpc/include/asm/sparsemem.h |  3 ++-
 arch/x86/include/asm/sparsemem.h     | 10 ++++++++++
 arch/x86/mm/numa.c                   |  2 ++
 drivers/dax/Kconfig                  |  1 -
 include/linux/memory_hotplug.h       | 14 --------------
 include/linux/numa.h                 | 28 +++++++++++++++++++++++++++-
 mm/memory_hotplug.c                  | 18 ------------------
 8 files changed, 45 insertions(+), 35 deletions(-)

diff --git a/arch/ia64/include/asm/sparsemem.h b/arch/ia64/include/asm/sparsemem.h
index 336d0570e1fa..0dfc1511a7a6 100644
--- a/arch/ia64/include/asm/sparsemem.h
+++ b/arch/ia64/include/asm/sparsemem.h
@@ -18,4 +18,8 @@
 #endif
 
 #endif /* CONFIG_SPARSEMEM */
+
+int memory_add_physaddr_to_nid(u64 addr);
+#define memory_add_physaddr_to_nid memory_add_physaddr_to_nid
+
 #endif /* _ASM_IA64_SPARSEMEM_H */
diff --git a/arch/powerpc/include/asm/sparsemem.h b/arch/powerpc/include/asm/sparsemem.h
index 1e6fa371cc38..52519d2c5713 100644
--- a/arch/powerpc/include/asm/sparsemem.h
+++ b/arch/powerpc/include/asm/sparsemem.h
@@ -16,6 +16,8 @@
 extern int create_section_mapping(unsigned long start, unsigned long end,
 				  int nid, pgprot_t prot);
 extern int remove_section_mapping(unsigned long start, unsigned long end);
+extern int memory_add_physaddr_to_nid(u64 start);
+#define memory_add_physaddr_to_nid memory_add_physaddr_to_nid
 
 #ifdef CONFIG_NUMA
 extern int hot_add_scn_to_nid(unsigned long scn_addr);
@@ -26,6 +28,5 @@ static inline int hot_add_scn_to_nid(unsigned long scn_addr)
 }
 #endif /* CONFIG_NUMA */
 #endif /* CONFIG_MEMORY_HOTPLUG */
-
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_SPARSEMEM_H */
diff --git a/arch/x86/include/asm/sparsemem.h b/arch/x86/include/asm/sparsemem.h
index 6bfc878f6771..6a9ccc1b2be5 100644
--- a/arch/x86/include/asm/sparsemem.h
+++ b/arch/x86/include/asm/sparsemem.h
@@ -28,4 +28,14 @@
 #endif
 
 #endif /* CONFIG_SPARSEMEM */
+
+#ifndef __ASSEMBLY__
+#ifdef CONFIG_NUMA_KEEP_MEMINFO
+extern int phys_to_target_node(phys_addr_t start);
+#define phys_to_target_node phys_to_target_node
+extern int memory_add_physaddr_to_nid(u64 start);
+#define memory_add_physaddr_to_nid memory_add_physaddr_to_nid
+#endif
+#endif /* __ASSEMBLY__ */
+
 #endif /* _ASM_X86_SPARSEMEM_H */
diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index 44148691d78b..5eb4dc2b97da 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -938,6 +938,7 @@ int phys_to_target_node(phys_addr_t start)
 
 	return meminfo_to_nid(&numa_reserved_meminfo, start);
 }
+EXPORT_SYMBOL_GPL(phys_to_target_node);
 
 int memory_add_physaddr_to_nid(u64 start)
 {
@@ -947,4 +948,5 @@ int memory_add_physaddr_to_nid(u64 start)
 		nid = numa_meminfo.blk[0].nid;
 	return nid;
 }
+EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
 #endif
diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index 567428e10b7b..d2834c2cfa10 100644
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -50,7 +50,6 @@ config DEV_DAX_HMEM
 	  Say M if unsure.
 
 config DEV_DAX_HMEM_DEVICES
-	depends on NUMA_KEEP_MEMINFO # for phys_to_target_node()
 	depends on DEV_DAX_HMEM && DAX=y
 	def_bool y
 
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index d65c6fdc5cfc..551093b74596 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -281,20 +281,6 @@ static inline bool movable_node_is_enabled(void)
 }
 #endif /* ! CONFIG_MEMORY_HOTPLUG */
 
-#ifdef CONFIG_NUMA
-extern int memory_add_physaddr_to_nid(u64 start);
-extern int phys_to_target_node(u64 start);
-#else
-static inline int memory_add_physaddr_to_nid(u64 start)
-{
-	return 0;
-}
-static inline int phys_to_target_node(u64 start)
-{
-	return 0;
-}
-#endif
-
 #if defined(CONFIG_MEMORY_HOTPLUG) || defined(CONFIG_DEFERRED_STRUCT_PAGE_INIT)
 /*
  * pgdat resizing functions
diff --git a/include/linux/numa.h b/include/linux/numa.h
index 8cb33ccfb671..301ff9ee69ed 100644
--- a/include/linux/numa.h
+++ b/include/linux/numa.h
@@ -2,6 +2,7 @@
 #ifndef _LINUX_NUMA_H
 #define _LINUX_NUMA_H
 #include <linux/types.h>
+#include <asm/sparsemem.h>
 
 #ifdef CONFIG_NODES_SHIFT
 #define NODES_SHIFT     CONFIG_NODES_SHIFT
@@ -23,11 +24,36 @@
 #ifdef CONFIG_NUMA
 /* Generic implementation available */
 int numa_map_to_online_node(int node);
-#else
+
+#ifndef memory_add_physaddr_to_nid
+static inline int memory_add_physaddr_to_nid(u64 start)
+{
+	pr_info_once("Unknown online node for memory at 0x%llx, assuming node 0\n",
+			start);
+	return 0;
+}
+#endif
+#ifndef phys_to_target_node
+static inline int phys_to_target_node(u64 start)
+{
+	pr_info_once("Unknown target node for memory at 0x%llx, assuming node 0\n",
+			start);
+	return 0;
+}
+#endif
+#else /* !CONFIG_NUMA */
 static inline int numa_map_to_online_node(int node)
 {
 	return NUMA_NO_NODE;
 }
+static inline int memory_add_physaddr_to_nid(u64 start)
+{
+	return 0;
+}
+static inline int phys_to_target_node(u64 start)
+{
+	return 0;
+}
 #endif
 
 #endif /* _LINUX_NUMA_H */
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index b44d4c7ba73b..63b2e46b6555 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -350,24 +350,6 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages,
 	return err;
 }
 
-#ifdef CONFIG_NUMA
-int __weak memory_add_physaddr_to_nid(u64 start)
-{
-	pr_info_once("Unknown online node for memory at 0x%llx, assuming node 0\n",
-			start);
-	return 0;
-}
-EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
-
-int __weak phys_to_target_node(u64 start)
-{
-	pr_info_once("Unknown target node for memory at 0x%llx, assuming node 0\n",
-			start);
-	return 0;
-}
-EXPORT_SYMBOL_GPL(phys_to_target_node);
-#endif
-
 /* find the smallest valid pfn in the range [start_pfn, end_pfn) */
 static unsigned long find_smallest_section_pfn(int nid, struct zone *zone,
 				     unsigned long start_pfn,
-- 
2.25.4


[-- Attachment #3: Type: text/plain, Size: 167 bytes --]

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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Randy Dunlap]

On 11/2/20 3:52 PM, Dan Williams wrote:
> On Sat, Oct 31, 2020 at 2:10 AM Christoph Hellwig <hch@infradead.org> wrote:
>>
>> On Thu, Oct 29, 2020 at 07:29:45PM -0700, Dan Williams wrote:
>>> The core-mm has a default __weak implementation of phys_to_target_node()
>>> when the architecture does not override it. That symbol is exported
>>> for modules. However, while the export in mm/memory_hotplug.c exported
>>> the symbol in the configuration cases of:
>>
>> Which just means that we should never export weak symbols.  So instead
>> of hacking around this introduce a symbol that indicates that the
>> architecture impements phys_to_target_node, and don't defined it at all
>> in common code for that case.
> 
> So I agree with this, but it made me realize that the way
> memory_add_physaddr_to_nid() was defined as an exported weak symbol is
> similarly broken.
> 
>>> --- a/mm/memory_hotplug.c
>>> +++ b/mm/memory_hotplug.c
>>> @@ -365,9 +365,14 @@ int __weak phys_to_target_node(u64 start)
>>>                       start);
>>>       return 0;
>>>  }
>>> +
>>> +/* If the arch did not export a strong symbol, export the weak one. */
>>> +#ifndef CONFIG_NUMA_KEEP_MEMINFO
>>>  EXPORT_SYMBOL_GPL(phys_to_target_node);
>>>  #endif
>>>
>>> +#endif
>>
>> i.e. move the ifdef to include the actual phys_to_target_node
>> definition, and remove the __weak from it here.
> 
> The trick is finding an arch common way to pick up the presence of the
> phys_to_target_node() override, and it still has the wart of ifdefery
> in C code.
> 
> I went a bit deeper and moved all the fallback routines to
> linux/numa.h and the overrides in all archs that care to
> asm/sparsemem.h. Note that asm/sparsemem.h was not my first choice,
> but it happened to be where powerpc was already defining its
> phys-addr-to-node-id infrastructure, and my first choice header,
> asm/numa.h, is not universally available.
> 
> The attached patch is going through some kbuild-robot exposure to make
> sure I did not break anything else.
> 

Works for me. Thanks.

Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested

-- 
~Randy
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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Christoph Hellwig]

This version looks sensible to me:

Reviewed-by: Christoph Hellwig <hch@lst.de>
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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Thomas Gleixner]

On Mon, Nov 02 2020 at 15:52, Dan Williams wrote:
> On Sat, Oct 31, 2020 at 2:10 AM Christoph Hellwig <hch@infradead.org> wrote:
> The dependency on NUMA_KEEP_MEMINFO for DEV_DAX_HMEM_DEVICES is invalid
> now that the symbol is properly exported / stubbed in all combinations
> of CONFIG_NUMA_KEEP_MEMINFO and CONFIG_MEMORY_HOTPLUG.
>
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Reported-by: Thomas Gleixner <tglx@linutronix.de>
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Christoph Hellwig <hch@infradead.org>
> Fixes: a035b6bf863e ("mm/memory_hotplug: introduce default phys_to_target_node() implementation")
> Cc: Joao Martins <joao.m.martins@oracle.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: x86@kernel.org
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: Fenghua Yu <fenghua.yu@intel.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Tested-by: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Andrew Morton]

On Mon, 2 Nov 2020 15:52:39 -0800 Dan Williams <dan.j.williams@intel.com> wrote:

> The attached patch is going through some kbuild-robot exposure to make
> sure I did not break anything else.

I'll duck this for now - please send it along formally if/when testing
is successful.
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Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Dan Williams]

On Tue, Nov 3, 2020 at 5:38 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Mon, 2 Nov 2020 15:52:39 -0800 Dan Williams <dan.j.williams@intel.com> wrote:
>
> > The attached patch is going through some kbuild-robot exposure to make
> > sure I did not break anything else.
>
> I'll duck this for now - please send it along formally if/when testing
> is successful.

Yeah, the robots are angry, some reworks needed.
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