linux-kernel - Re: [PATCH 1/3] x86/numa: Fix SRAT lookup for CFMWS ranges with numa_fill

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Date: Mon, 18 Mar 2024 14:26:41 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: Robert Richter <rrichter@....com>, "Rafael J. Wysocki"
	<rafael@...nel.org>, Alison Schofield <alison.schofield@...el.com>, "Dan
 Williams" <dan.j.williams@...el.com>, Dave Hansen
	<dave.hansen@...ux.intel.com>
CC: <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-cxl@...r.kernel.org>, Robert Richter <rrichter@....com>, Derick Marks
	<derick.w.marks@...el.com>, Len Brown <lenb@...nel.org>
Subject: Re: [PATCH 1/3] x86/numa: Fix SRAT lookup for CFMWS ranges with
 numa_fill_memblks()

Robert Richter wrote:
> With 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.
> 
> 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.
> 
> Fix this by enabling NUMA_KEEP_MEMINFO for x86 with ACPI and NUMA
> enabled.
> 
> [1] 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@...el.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Alison Schofield <alison.schofield@...el.com>
> Signed-off-by: Robert Richter <rrichter@....com>
> ---
>  drivers/acpi/numa/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/acpi/numa/Kconfig b/drivers/acpi/numa/Kconfig
> index 849c2bd820b9..2f4ac6ac6768 100644
> --- a/drivers/acpi/numa/Kconfig
> +++ b/drivers/acpi/numa/Kconfig
> @@ -3,6 +3,7 @@ config ACPI_NUMA
>  	bool "NUMA support"
>  	depends on NUMA
>  	depends on (X86 || ARM64 || LOONGARCH)
> +	select NUMA_KEEP_MEMINFO if X86
>  	default y if ARM64

A fix is needed, yes, but this is the wrong one. NUMA_KEEP_MEMINFO is
only about marking numa_meminfo data as not "__init". Since
numa_fill_memblks() *is* an __init function, it should have no
dependency on NUMA_KEEP_MEMINFO.

The fix here involves moving the definition of numa_fill_memblks() out
of the "#ifdef CONFIG_NUMA_KEEP_MEMINFO" in
arch/x86/include/asm/sparsemem.h so that it does not fallback to the
default definition in include/linux/numa.h.

It should also be the case that cxl_acpi needs this:

diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
index 67998dbd1d46..1bf25185c35b 100644
--- a/drivers/cxl/Kconfig
+++ b/drivers/cxl/Kconfig
@@ -6,6 +6,7 @@ menuconfig CXL_BUS
        select FW_UPLOAD
        select PCI_DOE
        select FIRMWARE_TABLE
+       select NUMA_KEEP_MEMINFO if NUMA
        help
          CXL is a bus that is electrically compatible with PCI Express, but
          layers three protocols on that signalling (CXL.io, CXL.cache, and