[v6,01/18] mm: Clarify the spec for set_ptes()

Message ID	20240215103205.2607016-2-ryan.roberts@arm.com (mailing list archive)
State	New
Headers	show Return-Path: <owner-linux-mm@kvack.org> From: Ryan Roberts <ryan.roberts@arm.com> To: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>, Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>, Andrey Ryabinin <ryabinin.a.a@gmail.com>, Andrew Morton <akpm@linux-foundation.org>, Matthew Wilcox <willy@infradead.org>, Mark Rutland <mark.rutland@arm.com>, David Hildenbrand <david@redhat.com>, Kefeng Wang <wangkefeng.wang@huawei.com>, John Hubbard <jhubbard@nvidia.com>, Zi Yan <ziy@nvidia.com>, Barry Song <21cnbao@gmail.com>, Alistair Popple <apopple@nvidia.com>, Yang Shi <shy828301@gmail.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, "H. Peter Anvin" <hpa@zytor.com> Cc: Ryan Roberts <ryan.roberts@arm.com>, linux-arm-kernel@lists.infradead.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v6 01/18] mm: Clarify the spec for set_ptes() Date: Thu, 15 Feb 2024 10:31:48 +0000 Message-Id: <20240215103205.2607016-2-ryan.roberts@arm.com> In-Reply-To: <20240215103205.2607016-1-ryan.roberts@arm.com> References: <20240215103205.2607016-1-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org Precedence: bulk
Series	Transparent Contiguous PTEs for User Mappings \| expand [v6,00/18] Transparent Contiguous PTEs for User Mappings [v6,01/18] mm: Clarify the spec for set_ptes() [v6,02/18] mm: thp: Batch-collapse PMD with set_ptes() [v6,03/18] mm: Introduce pte_advance_pfn() and use for pte_next_pfn() [v6,04/18] arm64/mm: Convert pte_next_pfn() to pte_advance_pfn() [v6,05/18] x86/mm: Convert pte_next_pfn() to pte_advance_pfn() [v6,06/18] mm: Tidy up pte_next_pfn() definition [v6,07/18] arm64/mm: Convert READ_ONCE(*ptep) to ptep_get(ptep) [v6,08/18] arm64/mm: Convert set_pte_at() to set_ptes(..., 1) [v6,09/18] arm64/mm: Convert ptep_clear() to ptep_get_and_clear() [v6,10/18] arm64/mm: New ptep layer to manage contig bit [v6,11/18] arm64/mm: Split __flush_tlb_range() to elide trailing DSB [v6,12/18] arm64/mm: Wire up PTE_CONT for user mappings [v6,13/18] arm64/mm: Implement new wrprotect_ptes() batch API [v6,14/18] arm64/mm: Implement new [get_and_]clear_full_ptes() batch APIs [v6,15/18] mm: Add pte_batch_hint() to reduce scanning in folio_pte_batch() [v6,16/18] arm64/mm: Implement pte_batch_hint() [v6,17/18] arm64/mm: __always_inline to improve fork() perf [v6,18/18] arm64/mm: Automatically fold contpte mappings

Message ID

20240215103205.2607016-2-ryan.roberts@arm.com (mailing list archive)

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New

Headers

From: Ryan Roberts <ryan.roberts@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Ard Biesheuvel <ardb@kernel.org>,
	Marc Zyngier <maz@kernel.org>,
	James Morse <james.morse@arm.com>,
	Andrey Ryabinin <ryabinin.a.a@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Matthew Wilcox <willy@infradead.org>,
	Mark Rutland <mark.rutland@arm.com>,
	David Hildenbrand <david@redhat.com>,
	Kefeng Wang <wangkefeng.wang@huawei.com>,
	John Hubbard <jhubbard@nvidia.com>,
	Zi Yan <ziy@nvidia.com>,
	Barry Song <21cnbao@gmail.com>,
	Alistair Popple <apopple@nvidia.com>,
	Yang Shi <shy828301@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	x86@kernel.org,
	linuxppc-dev@lists.ozlabs.org,
	linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v6 01/18] mm: Clarify the spec for set_ptes()
Date: Thu, 15 Feb 2024 10:31:48 +0000
Message-Id: <20240215103205.2607016-2-ryan.roberts@arm.com>
In-Reply-To: <20240215103205.2607016-1-ryan.roberts@arm.com>
References: <20240215103205.2607016-1-ryan.roberts@arm.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: owner-linux-mm@kvack.org
Precedence: bulk

Series

Transparent Contiguous PTEs for User Mappings | expand

Commit Message

Ryan Roberts Feb. 15, 2024, 10:31 a.m. UTC

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@redhat.com>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.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.
  *

[v6,01/18] mm: Clarify the spec for set_ptes()

Commit Message

Patch