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Message-Id: <20240215103205.2607016-2-ryan.roberts@arm.com>
Date: Thu, 15 Feb 2024 10:31:48 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Ard Biesheuvel <ardb@...nel.org>,
Marc Zyngier <maz@...nel.org>,
James Morse <james.morse@....com>,
Andrey Ryabinin <ryabinin.a.a@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Matthew Wilcox <willy@...radead.org>,
Mark Rutland <mark.rutland@....com>,
David Hildenbrand <david@...hat.com>,
Kefeng Wang <wangkefeng.wang@...wei.com>,
John Hubbard <jhubbard@...dia.com>,
Zi Yan <ziy@...dia.com>,
Barry Song <21cnbao@...il.com>,
Alistair Popple <apopple@...dia.com>,
Yang Shi <shy828301@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>
Cc: Ryan Roberts <ryan.roberts@....com>,
linux-arm-kernel@...ts.infradead.org,
x86@...nel.org,
linuxppc-dev@...ts.ozlabs.org,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v6 01/18] mm: Clarify the spec for set_ptes()
set_ptes() spec implies that it can only be used to set a present pte
because it interprets the PFN field to increment it. However,
set_pte_at() has been implemented on top of set_ptes() since set_ptes()
was introduced, and set_pte_at() allows setting a pte to a not-present
state. So clarify the spec to state that when nr==1, new state of pte
may be present or not present. When nr>1, new state of all ptes must be
present.
While we are at it, tighten the spec to set requirements around the
initial state of ptes; when nr==1 it may be either present or
not-present. But when nr>1 all ptes must initially be not-present. All
set_ptes() callsites already conform to this requirement. Stating it
explicitly is useful because it allows for a simplification to the
upcoming arm64 contpte implementation.
Acked-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Ryan Roberts <ryan.roberts@....com>
---
include/linux/pgtable.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 49ab1f73b5c2..231370e1b80f 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -229,6 +229,10 @@ static inline pte_t pte_next_pfn(pte_t pte)
* @pte: Page table entry for the first page.
* @nr: Number of pages to map.
*
+ * When nr==1, initial state of pte may be present or not present, and new state
+ * may be present or not present. When nr>1, initial state of all ptes must be
+ * not present, and new state must be present.
+ *
* May be overridden by the architecture, or the architecture can define
* set_pte() and PFN_PTE_SHIFT.
*
--
2.25.1
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