linux-kernel - [PATCH 2/4] mm: rmap: Allow platforms without mm

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]

Date:   Fri,  8 Jul 2022 00:52:40 +1200
From:   Barry Song <21cnbao@...il.com>
To:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org, x86@...nel.org,
        catalin.marinas@....com, will@...nel.org, linux-doc@...r.kernel.org
Cc:     corbet@....net, arnd@...db.de, linux-kernel@...r.kernel.org,
        darren@...amperecomputing.com, yangyicong@...ilicon.com,
        huzhanyuan@...o.com, lipeifeng@...o.com, zhangshiming@...o.com,
        guojian@...o.com, realmz6@...il.com,
        Barry Song <v-songbaohua@...o.com>,
        Nadav Amit <namit@...are.com>, Mel Gorman <mgorman@...e.de>
Subject: [PATCH 2/4] mm: rmap: Allow platforms without mm_cpumask to defer TLB flush

From: Barry Song <v-songbaohua@...o.com>

Platforms like ARM64 have hareware TLB shootdown broadcast. They
don't maintain mm_cpumask and they just send tlbi and related
sync instructions for TLB flush.
So if mm_cpumask is empty, we also allow deferred TLB flush

Cc: Nadav Amit <namit@...are.com>
Cc: Mel Gorman <mgorman@...e.de>
Signed-off-by: Barry Song <v-songbaohua@...o.com>>
---
 mm/rmap.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 5bcb334cd6f2..d320c29a4ad8 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -692,8 +692,13 @@ static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
 	if (!(flags & TTU_BATCH_FLUSH))
 		return false;
 
-	/* If remote CPUs need to be flushed then defer batch the flush */
-	if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
+	/*
+	 * If remote CPUs need to be flushed then defer batch the flush;
+	 * If ARCHs like ARM64 have hardware TLB flush broadcast, thus
+	 * they don't maintain mm_cpumask() at all, defer batch as well.
+	 */
+	if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids ||
+	    cpumask_empty(mm_cpumask(mm)))
 		should_defer = true;
 	put_cpu();
 
-- 
2.25.1