linux-kernel - [PATCH RFC 27/37] arm64: mte: Reserve tag block for the zero page

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Message-Id: <20230823131350.114942-28-alexandru.elisei@arm.com>
Date:   Wed, 23 Aug 2023 14:13:40 +0100
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,
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        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,
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Subject: [PATCH RFC 27/37] 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 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 7dff93492a7b..1ab875be5f9b 100644
--- a/arch/arm64/kernel/mte_tag_storage.c
+++ b/arch/arm64/kernel/mte_tag_storage.c
@@ -398,6 +398,8 @@ static int __init mte_tag_storage_activate_regions(void)
 		}
 	}
 
+	ret = reserve_metadata_storage(ZERO_PAGE(0), 0, GFP_HIGHUSER_MOVABLE);
+
 	return ret;
 }
 core_initcall(mte_tag_storage_activate_regions);
-- 
2.41.0