RE: [PATCH v3 1/5] x86/numa: Fix SRAT lookup of CFMWS ranges with numa_fill_memblks()

[Dan Williams]

Robert Richter wrote:
> For configurations that have the kconfig option NUMA_KEEP_MEMINFO
> disabled, the SRAT lookup done with numa_fill_memblks() fails
> returning NUMA_NO_MEMBLK (-1). An existing SRAT memory range cannot be
> found for a CFMWS address range. This causes the addition of a
> duplicate numa_memblk with a different node id and a subsequent page
> fault and kernel crash during boot.
> 
> numa_fill_memblks() is implemented and used in the init section only.
> The option NUMA_KEEP_MEMINFO is only for the case when NUMA data will
> be used outside of init. So fix the SRAT lookup by moving
> numa_fill_memblks() out of the NUMA_KEEP_MEMINFO block to make it
> always available in the init section.
> 
> Note that the issue was initially introduced with [1]. But since
> phys_to_target_node() was originally used that returned the valid node
> 0, an additional numa_memblk was not added. Though, the node id was
> wrong too.

Wrong node seems worth notifying and we can figure out on the backend
where the backport makes sense.

> 
> [1] commit fd49f99c1809 ("ACPI: NUMA: Add a node and memblk for each
>     CFMWS not in SRAT")
> 
> Fixes: 8f1004679987 ("ACPI/NUMA: Apply SRAT proximity domain to entire CFMWS window")
> Cc: Derick Marks <derick.w.marks@xxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Alison Schofield <alison.schofield@xxxxxxxxx>
> Signed-off-by: Robert Richter <rrichter@xxxxxxx>
> ---
>  arch/x86/include/asm/sparsemem.h | 2 +-
>  arch/x86/mm/numa.c               | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/sparsemem.h b/arch/x86/include/asm/sparsemem.h
> index 1be13b2dfe8b..1aaa447ef24b 100644
> --- a/arch/x86/include/asm/sparsemem.h
> +++ b/arch/x86/include/asm/sparsemem.h
> @@ -37,9 +37,9 @@ 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
>  extern int numa_fill_memblks(u64 start, u64 end);
>  #define numa_fill_memblks numa_fill_memblks

It just feels like numa_fill_memblks() has absolutely no business being
defined in arch/x86/include/asm/sparsemem.h.

The only use for numa_fill_memblks() is to arrange for NUMA nodes to be
applied to memory ranges hot-onlined by the CXL driver.

It belongs right next to numa_add_memblk(), and I suspect
arch/x86/include/asm/sparsemem.h was only chosen to avoid figuring out
what to do about the fact that linux/numa.h does not include asm/numa.h
and that all implementations either provide numa_add_memblk() or select
the generic implementation.

So I would prefer that this do the proper fix and get
numa_fill_memblks() completely out of the sparsemem.h path.

Something like the following which boots for me:

diff --git a/arch/x86/include/asm/numa.h b/arch/x86/include/asm/numa.h
index ef2844d69173..12a93a3466c4 100644
--- a/arch/x86/include/asm/numa.h
+++ b/arch/x86/include/asm/numa.h
@@ -26,6 +26,7 @@ extern s16 __apicid_to_node[MAX_LOCAL_APIC];
 extern nodemask_t numa_nodes_parsed __initdata;
 
 extern int __init numa_add_memblk(int nodeid, u64 start, u64 end);
+extern int __init numa_fill_memblks(u64 start, u64 end);
 extern void __init numa_set_distance(int from, int to, int distance);
 
 static inline void set_apicid_to_node(int apicid, s16 node)
diff --git a/arch/x86/include/asm/sparsemem.h b/arch/x86/include/asm/sparsemem.h
index 1be13b2dfe8b..64df897c0ee3 100644
--- a/arch/x86/include/asm/sparsemem.h
+++ b/arch/x86/include/asm/sparsemem.h
@@ -37,8 +37,6 @@ 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
-extern int numa_fill_memblks(u64 start, u64 end);
-#define numa_fill_memblks numa_fill_memblks
 #endif
 #endif /* __ASSEMBLY__ */
 
diff --git a/drivers/acpi/numa/srat.c b/drivers/acpi/numa/srat.c
index e45e64993c50..3b09fd39eeb4 100644
--- a/drivers/acpi/numa/srat.c
+++ b/drivers/acpi/numa/srat.c
@@ -208,6 +208,11 @@ int __init srat_disabled(void)
 	return acpi_numa < 0;
 }
 
+__weak int __init numa_fill_memblks(u64 start, u64 end)
+{
+	return NUMA_NO_MEMBLK;
+}
+
 #if defined(CONFIG_X86) || defined(CONFIG_ARM64) || defined(CONFIG_LOONGARCH)
 /*
  * Callback for SLIT parsing.  pxm_to_node() returns NUMA_NO_NODE for
diff --git a/include/linux/numa.h b/include/linux/numa.h
index 915033a75731..8485d98e554d 100644
--- a/include/linux/numa.h
+++ b/include/linux/numa.h
@@ -36,13 +36,6 @@ int memory_add_physaddr_to_nid(u64 start);
 int phys_to_target_node(u64 start);
 #endif
 
-#ifndef numa_fill_memblks
-static inline int __init numa_fill_memblks(u64 start, u64 end)
-{
-	return NUMA_NO_MEMBLK;
-}
-#endif
-
 #else /* !CONFIG_NUMA */
 static inline int numa_nearest_node(int node, unsigned int state)
 {