linux-kernel - [PATCH RFC v2 18/27] arm64: mte: Reserve tag block for the zero page

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Date:   Sun, 19 Nov 2023 16:57:12 +0000
From:   Alexandru Elisei <alexandru.elisei@....com>
To:     catalin.marinas@....com, will@...nel.org, oliver.upton@...ux.dev,
        maz@...nel.org, james.morse@....com, suzuki.poulose@....com,
        yuzenghui@...wei.com, arnd@...db.de, akpm@...ux-foundation.org,
        mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com, mhiramat@...nel.org,
        rppt@...nel.org, hughd@...gle.com
Cc:     pcc@...gle.com, steven.price@....com, anshuman.khandual@....com,
        vincenzo.frascino@....com, david@...hat.com, eugenis@...gle.com,
        kcc@...gle.com, hyesoo.yu@...sung.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
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        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-trace-kernel@...r.kernel.org
Subject: [PATCH RFC v2 18/27] arm64: mte: Reserve tag block for the zero page

On arm64, the zero page receives special treatment by having the tagged
flag set on MTE initialization, not when the page is mapped in a process
address space. Reserve the corresponding tag block when tag storage
management is being activated.

Signed-off-by: Alexandru Elisei <alexandru.elisei@....com>
---
 arch/arm64/kernel/mte_tag_storage.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/kernel/mte_tag_storage.c b/arch/arm64/kernel/mte_tag_storage.c
index 833480048170..a1cc239f7211 100644
--- a/arch/arm64/kernel/mte_tag_storage.c
+++ b/arch/arm64/kernel/mte_tag_storage.c
@@ -393,6 +393,8 @@ static int __init mte_tag_storage_activate_regions(void)
 		totalcma_pages += range_len(tag_range);
 	}
 
+	reserve_tag_storage(ZERO_PAGE(0), 0, GFP_HIGHUSER_MOVABLE);
+
 	return 0;
 
 out_disabled:
-- 
2.42.1