Re: [PATCH] arch_numa: Restore nid checks before registering a memblock with a node

[Mike Rapoport <rppt@kernel.org>]

On Fri, Nov 29, 2024 at 08:42:55AM +0000, Marc Zyngier wrote:
> On Fri, 29 Nov 2024 08:24:16 +0000,
> Mike Rapoport <rppt@kernel.org> wrote:
> > 
> > On Thu, Nov 28, 2024 at 04:52:14PM +0000, Marc Zyngier wrote:
> > > Hi Mike,
> > > 
> > > On Thu, 28 Nov 2024 07:03:33 +0000,
> > > Mike Rapoport <rppt@kernel.org> wrote:
> > > > 
> > > > Hi Marc,
> > > > 
> > > > > diff --git a/drivers/base/arch_numa.c b/drivers/base/arch_numa.c
> > > > > index e187016764265..5457248eb0811 100644
> > > > > --- a/drivers/base/arch_numa.c
> > > > > +++ b/drivers/base/arch_numa.c
> > > > > @@ -207,7 +207,21 @@ static void __init setup_node_data(int nid, u64 start_pfn, u64 end_pfn)
> > > > >  static int __init numa_register_nodes(void)
> > > > >  {
> > > > >  	int nid;
> > > > > -
> > > > > +	struct memblock_region *mblk;
> > > > > +
> > > > > +	/* Check that valid nid is set to memblks */
> > > > > +	for_each_mem_region(mblk) {
> > > > > +		int mblk_nid = memblock_get_region_node(mblk);
> > > > > +		phys_addr_t start = mblk->base;
> > > > > +		phys_addr_t end = mblk->base + mblk->size - 1;
> > > > > +
> > > > > +		if (mblk_nid == NUMA_NO_NODE || mblk_nid >= MAX_NUMNODES) {
> > > > > +			pr_warn("Warning: invalid memblk node %d [mem %pap-%pap]\n",
> > > > > +				mblk_nid, &start, &end);
> > > > > +			return -EINVAL;
> > > > > +		}
> > > > 
> > > > We have memblock_validate_numa_coverage() that checks that amount of memory
> > > > with unset node id is less than a threshold. The loop here can be replaced
> > > > with something like
> > > > 
> > > > 	if (!memblock_validate_numa_coverage(0))
> > > > 		return -EINVAL;
> > > 
> > > Unfortunately, that doesn't seem to result in something that works
> > > (relevant extract only):
> > > 
> > > [    0.000000] NUMA: no nodes coverage for 9MB of 65516MB RAM
> > > [    0.000000] NUMA: Faking a node at [mem 0x0000000000500000-0x0000000fff0fffff]
> > > [    0.000000] NUMA: no nodes coverage for 0MB of 65516MB RAM
> > > [    0.000000] Unable to handle kernel paging request at virtual address 0000000000001d40
> > > 
> > > Any idea?
> > 
> > With 0 as the threshold the validation fails for the fake node, but it
> > should be fine with memblock_validate_numa_coverage(1)
> 
> Huh, subtle. This indeed seems to work. I'll respin the patch next week.

With the patch below memblock_validate_numa_coverage(0) should also work
and it makes more sense.

@Andrew, I can take both this and Marc's new patch via memblock tree if you
prefer.

From de55af44c02bc9aa43f05a785ac66a5aafa43354 Mon Sep 17 00:00:00 2001
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
Date: Fri, 29 Nov 2024 11:13:47 +0200
Subject: [PATCH] memblock: allow zero threshold in validate_numa_converage()

Currently memblock validate_numa_converage() returns false negative when
threshold set to zero.

Make the check if the memory size with invalid node ID is greater than
the threshold exclusive to fix that.

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 mm/memblock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index 0389ce5cd281..095c18b5c430 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -735,7 +735,7 @@ int __init_memblock memblock_add(phys_addr_t base, phys_addr_t size)
 /**
  * memblock_validate_numa_coverage - check if amount of memory with
  * no node ID assigned is less than a threshold
- * @threshold_bytes: maximal number of pages that can have unassigned node
+ * @threshold_bytes: maximal memory size that can have unassigned node
  * ID (in bytes).
  *
  * A buggy firmware may report memory that does not belong to any node.
@@ -755,7 +755,7 @@ bool __init_memblock memblock_validate_numa_coverage(unsigned long threshold_byt
 			nr_pages += end_pfn - start_pfn;
 	}
 
-	if ((nr_pages << PAGE_SHIFT) >= threshold_bytes) {
+	if ((nr_pages << PAGE_SHIFT) > threshold_bytes) {
 		mem_size_mb = memblock_phys_mem_size() >> 20;
 		pr_err("NUMA: no nodes coverage for %luMB of %luMB RAM\n",
 		       (nr_pages << PAGE_SHIFT) >> 20, mem_size_mb);
-- 
2.45.2

 
> Thanks for your help,
> 
> 	M.

-- 
Sincerely yours,
Mike.