linux-kernel - [PATCH v3 2/3] x86: probe memory block size advisement value during mm init

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20241022213450.15041-3-gourry@gourry.net>
Date: Tue, 22 Oct 2024 17:34:49 -0400
From: Gregory Price <gourry@...rry.net>
To: x86@...nel.org,
	linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	linux-mm@...ck.org
Cc: linux-cxl@...ck.org,
	Jonathan.Cameron@...wei.com,
	dan.j.williams@...el.com,
	rrichter@....com,
	Terry.Bowman@....com,
	dave.jiang@...el.com,
	ira.weiny@...el.com,
	alison.schofield@...el.com,
	gourry@...rry.net,
	dave.hansen@...ux.intel.com,
	luto@...nel.org,
	peterz@...radead.org,
	tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	hpa@...or.com,
	rafael@...nel.org,
	lenb@...nel.org,
	david@...hat.com,
	osalvador@...e.de,
	gregkh@...uxfoundation.org,
	akpm@...ux-foundation.org,
	rppt@...nel.org
Subject: [PATCH v3 2/3] x86: probe memory block size advisement value during mm init

Systems with hotplug may provide an advisement value on what the
memblock size should be.  Probe this value when the rest of the
configuration values are considered.

The new heuristic is as follows

1) set_memory_block_size_order value if already set (cmdline param)
2) minimum block size if memory is less than large block limit
3) if no hotplug advice: Max block size if system is bare-metal,
   otherwise use end of memory alignment.
4) if hotplug advice: lesser of advice and end of memory alignment.

Suggested-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Gregory Price <gourry@...rry.net>
---
 arch/x86/mm/init_64.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index ff253648706f..93d669f467f7 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1452,13 +1452,17 @@ static unsigned long probe_memory_block_size(void)
 	}
 
 	/*
-	 * Use max block size to minimize overhead on bare metal, where
-	 * alignment for memory hotplug isn't a concern.
+	 * When hotplug alignment is not a concern, maximize blocksize
+	 * to minimize overhead. Otherwise, align to the lesser of advice
+	 * alignment and end of memory alignment.
 	 */
-	if (!boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
+	bz = memory_block_probe_max_size();
+	if (!bz) {
 		bz = MAX_BLOCK_SIZE;
-		goto done;
-	}
+		if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
+			goto done;
+	} else
+		bz = max(min(bz, MAX_BLOCK_SIZE), MIN_MEMORY_BLOCK_SIZE);
 
 	/* Find the largest allowed block size that aligns to memory end */
 	for (bz = MAX_BLOCK_SIZE; bz > MIN_MEMORY_BLOCK_SIZE; bz >>= 1) {
-- 
2.43.0