Patch "x86/numa: Introduce numa_fill_memblks()" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    x86/numa: Introduce numa_fill_memblks()

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-numa-introduce-numa_fill_memblks.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 629df80a4e8756382550c7d79b24c4801c0b62ee
Author: Alison Schofield <alison.schofield@xxxxxxxxx>
Date:   Mon Jul 10 13:02:58 2023 -0700

    x86/numa: Introduce numa_fill_memblks()
    
    [ Upstream commit 8f012db27c9516be1a7aca93ea4a6ca9c75056c9 ]
    
    numa_fill_memblks() fills in the gaps in numa_meminfo memblks
    over an physical address range.
    
    The ACPI driver will use numa_fill_memblks() to implement a new Linux
    policy that prescribes extending proximity domains in a portion of a
    CFMWS window to the entire window.
    
    Dan Williams offered this explanation of the policy:
    A CFWMS is an ACPI data structure that indicates *potential* locations
    where CXL memory can be placed. It is the playground where the CXL
    driver has free reign to establish regions. That space can be populated
    by BIOS created regions, or driver created regions, after hotplug or
    other reconfiguration.
    
    When BIOS creates a region in a CXL Window it additionally describes
    that subset of the Window range in the other typical ACPI tables SRAT,
    SLIT, and HMAT. The rationale for BIOS not pre-describing the entire
    CXL Window in SRAT, SLIT, and HMAT is that it can not predict the
    future. I.e. there is nothing stopping higher or lower performance
    devices being placed in the same Window. Compare that to ACPI memory
    hotplug that just onlines additional capacity in the proximity domain
    with little freedom for dynamic performance differentiation.
    
    That leaves the OS with a choice, should unpopulated window capacity
    match the proximity domain of an existing region, or should it allocate
    a new one? This patch takes the simple position of minimizing proximity
    domain proliferation by reusing any proximity domain intersection for
    the entire Window. If the Window has no intersections then allocate a
    new proximity domain. Note that SRAT, SLIT and HMAT information can be
    enumerated dynamically in a standard way from device provided data.
    Think of CXL as the end of ACPI needing to describe memory attributes,
    CXL offers a standard discovery model for performance attributes, but
    Linux still needs to interoperate with the old regime.
    
    Reported-by: Derick Marks <derick.w.marks@xxxxxxxxx>
    Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
    Signed-off-by: Alison Schofield <alison.schofield@xxxxxxxxx>
    Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
    Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
    Tested-by: Derick Marks <derick.w.marks@xxxxxxxxx>
    Link: https://lore.kernel.org/all/ef078a6f056ca974e5af85997013c0fda9e3326d.1689018477.git.alison.schofield%40intel.com
    Stable-dep-of: 8f1004679987 ("ACPI/NUMA: Apply SRAT proximity domain to entire CFMWS window")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/x86/include/asm/sparsemem.h b/arch/x86/include/asm/sparsemem.h
index 64df897c0ee30..1be13b2dfe8bf 100644
--- a/arch/x86/include/asm/sparsemem.h
+++ b/arch/x86/include/asm/sparsemem.h
@@ -37,6 +37,8 @@ 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/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index 2aadb2019b4f2..c01c5506fd4ae 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -11,6 +11,7 @@
 #include <linux/nodemask.h>
 #include <linux/sched.h>
 #include <linux/topology.h>
+#include <linux/sort.h>
 
 #include <asm/e820/api.h>
 #include <asm/proto.h>
@@ -961,4 +962,83 @@ int memory_add_physaddr_to_nid(u64 start)
 	return nid;
 }
 EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
+
+static int __init cmp_memblk(const void *a, const void *b)
+{
+	const struct numa_memblk *ma = *(const struct numa_memblk **)a;
+	const struct numa_memblk *mb = *(const struct numa_memblk **)b;
+
+	return ma->start - mb->start;
+}
+
+static struct numa_memblk *numa_memblk_list[NR_NODE_MEMBLKS] __initdata;
+
+/**
+ * numa_fill_memblks - Fill gaps in numa_meminfo memblks
+ * @start: address to begin fill
+ * @end: address to end fill
+ *
+ * Find and extend numa_meminfo memblks to cover the @start-@end
+ * physical address range, such that the first memblk includes
+ * @start, the last memblk includes @end, and any gaps in between
+ * are filled.
+ *
+ * RETURNS:
+ * 0		  : Success
+ * NUMA_NO_MEMBLK : No memblk exists in @start-@end range
+ */
+
+int __init numa_fill_memblks(u64 start, u64 end)
+{
+	struct numa_memblk **blk = &numa_memblk_list[0];
+	struct numa_meminfo *mi = &numa_meminfo;
+	int count = 0;
+	u64 prev_end;
+
+	/*
+	 * Create a list of pointers to numa_meminfo memblks that
+	 * overlap start, end. Exclude (start == bi->end) since
+	 * end addresses in both a CFMWS range and a memblk range
+	 * are exclusive.
+	 *
+	 * This list of pointers is used to make in-place changes
+	 * that fill out the numa_meminfo memblks.
+	 */
+	for (int i = 0; i < mi->nr_blks; i++) {
+		struct numa_memblk *bi = &mi->blk[i];
+
+		if (start < bi->end && end >= bi->start) {
+			blk[count] = &mi->blk[i];
+			count++;
+		}
+	}
+	if (!count)
+		return NUMA_NO_MEMBLK;
+
+	/* Sort the list of pointers in memblk->start order */
+	sort(&blk[0], count, sizeof(blk[0]), cmp_memblk, NULL);
+
+	/* Make sure the first/last memblks include start/end */
+	blk[0]->start = min(blk[0]->start, start);
+	blk[count - 1]->end = max(blk[count - 1]->end, end);
+
+	/*
+	 * Fill any gaps by tracking the previous memblks
+	 * end address and backfilling to it if needed.
+	 */
+	prev_end = blk[0]->end;
+	for (int i = 1; i < count; i++) {
+		struct numa_memblk *curr = blk[i];
+
+		if (prev_end >= curr->start) {
+			if (prev_end < curr->end)
+				prev_end = curr->end;
+		} else {
+			curr->start = prev_end;
+			prev_end = curr->end;
+		}
+	}
+	return 0;
+}
+
 #endif
diff --git a/include/linux/numa.h b/include/linux/numa.h
index 59df211d051fa..0f512c0aba54b 100644
--- a/include/linux/numa.h
+++ b/include/linux/numa.h
@@ -12,6 +12,7 @@
 #define MAX_NUMNODES    (1 << NODES_SHIFT)
 
 #define	NUMA_NO_NODE	(-1)
+#define	NUMA_NO_MEMBLK	(-1)
 
 /* optionally keep NUMA memory info available post init */
 #ifdef CONFIG_NUMA_KEEP_MEMINFO
@@ -43,6 +44,12 @@ static inline int phys_to_target_node(u64 start)
 	return 0;
 }
 #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_map_to_online_node(int node)
 {



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