linux-kernel - [PATCH v2 RESEND 1/2] arm64: avoid flushing icache multiple times on contiguous HugeTLB

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-next>] [day] [month] [year] [list]

Message-Id: <20220302084624.33340-1-songmuchun@bytedance.com>
Date:   Wed,  2 Mar 2022 16:46:23 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     will@...nel.org, akpm@...ux-foundation.org, david@...hat.com,
        bodeddub@...zon.com, osalvador@...e.de, mike.kravetz@...cle.com,
        rientjes@...gle.com, mark.rutland@....com, catalin.marinas@....com,
        james.morse@....com, song.bao.hua@...ilicon.com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, duanxiongchun@...edance.com,
        fam.zheng@...edance.com, smuchun@...il.com,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v2 RESEND 1/2] arm64: avoid flushing icache multiple times on contiguous HugeTLB

When a contiguous HugeTLB page is mapped, set_pte_at() will be called
CONT_PTES/CONT_PMDS times.  Therefore, __sync_icache_dcache() will
flush cache multiple times if the page is executable (to ensure
the I-D cache coherency).  However, the first flushing cache already
covers subsequent cache flush operations.  So only flusing cache
for the head page if it is a HugeTLB page to avoid redundant cache
flushing.  In the next patch, it is also depends on this change
since the tail vmemmap pages of HugeTLB is mapped with read-only
meanning only head page struct can be modified.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 arch/arm64/mm/flush.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
index 2aaf950b906c..a06c6ac770d4 100644
--- a/arch/arm64/mm/flush.c
+++ b/arch/arm64/mm/flush.c
@@ -52,6 +52,13 @@ void __sync_icache_dcache(pte_t pte)
 {
 	struct page *page = pte_page(pte);
 
+	/*
+	 * HugeTLB pages are always fully mapped, so only setting head page's
+	 * PG_dcache_clean flag is enough.
+	 */
+	if (PageHuge(page))
+		page = compound_head(page);
+
 	if (!test_bit(PG_dcache_clean, &page->flags)) {
 		sync_icache_aliases((unsigned long)page_address(page),
 				    (unsigned long)page_address(page) +
-- 
2.11.0