linux-kernel - Re: [PATCH v6 1/7] x86/numa: Fix SRAT lookup of CFMWS ranges with numa_fill

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Date: Tue, 30 Apr 2024 09:42:04 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: Robert Richter <rrichter@....com>, "Rafael J. Wysocki"
	<rafael@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar
	<mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
	<dave.hansen@...ux.intel.com>, <x86@...nel.org>, Andy Lutomirski
	<luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Alison Schofield
	<alison.schofield@...el.com>, Dan Williams <dan.j.williams@...el.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>, "H. Peter Anvin" <hpa@...or.com>, Len Brown
	<lenb@...nel.org>
Subject: Re: [PATCH v6 1/7] x86/numa: Fix SRAT lookup of CFMWS ranges with
 numa_fill_memblks()

Robert Richter wrote:
> For configurations that have the kconfig option NUMA_KEEP_MEMINFO
> disabled numa_fill_memblks() only returns with NUMA_NO_MEMBLK (-1).
> SRAT lookup fails then because 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.
> 
> Fix this by making numa_fill_memblks() always available regardless of
> NUMA_KEEP_MEMINFO.
> 
> The fix also removes numa_fill_memblks() from sparsemem.h using
> __weak.
> 
> From Dan:
> 
> """
> 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.
> """
> 
> 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, a message is seen then in the logs:
> 
>  kernel/numa.c:  pr_info_once("Unknown target node for memory at 0x%llx, assuming node 0\n",
> 
> [1] commit fd49f99c1809 ("ACPI: NUMA: Add a node and memblk for each
>     CFMWS not in SRAT")
> 
> Suggested-by: Dan Williams <dan.j.williams@...el.com>
> Link: https://lore.kernel.org/all/66271b0072317_69102944c@dwillia2-xfh.jf.intel.com.notmuch/
> 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>

Looks good,

Reviewed-by: Dan Williams <dan.j.williams@...el.com>