linux-kernel - Re: [PATCH v3 1/5] x86/numa: Fix SRAT lookup of CFMWS ranges with numa_fill

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Date: Wed, 24 Apr 2024 17:41:19 +0200
From: Robert Richter <rrichter@....com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: "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>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-cxl@...r.kernel.org, Derick Marks <derick.w.marks@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v3 1/5] x86/numa: Fix SRAT lookup of CFMWS ranges with
 numa_fill_memblks()

On 22.04.24 19:20:48, Dan Williams wrote:
> 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.

Updating the description here.

> 
> > 
> > [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@...el.com>
> > Cc: Dan Williams <dan.j.williams@...el.com>
> > Cc: Alison Schofield <alison.schofield@...el.com>
> > Signed-off-by: Robert Richter <rrichter@....com>
> > ---
> >  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:

I have kept this patch as a stable change but took your patch on top.

Thanks,

-Robert