From: Dave Hansen <dave.hansen@intel.com>
To: "David Hildenbrand (Arm)" <david@kernel.org>,
Yeoreum Yun <yeoreum.yun@arm.com>,
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Subject: Re: [RFC PATCH 10/34] x86: mm: carve out the generic compile-time folded pgtable case in effective_prot()
Date: Mon, 13 Jul 2026 10:57:18 -0700 [thread overview]
Message-ID: <32d459d1-ad19-4baf-bbb1-0565458001d2@intel.com> (raw)
In-Reply-To: <6007625e-c3f9-4ad6-99a8-61396bccbcec@kernel.org>
On 7/13/26 08:02, David Hildenbrand (Arm) wrote:
> It's always been the latter:
>
> ...folding => PUD => PMD => PTE
This is kinda arguing semantics, and there are different ways to look at
it. But I'd argue it couldn't *possibly* have always been this way.
Linux hasn't always had a PUD or a PMD for that matter. The i386 only
had two levels. PAE support was added later.
I think the pmd_t came with Alpha support (before my time) and pud_t
came later IIRC. I'm pretty sure Linux didn't have a pud_t when I first
started hacking on it circa 2001.
Second (and again this is my subjective opinion) a pgd_t* has always
been the "top" or "base" of the page tables. This is why there's an
mm->pgd and not an mm->pud. We've also talked *forever* about things
like a "special pgd" for the LDT remap. Or having two pgd pages for KPTI.
My point is that the PGD hasn't itself ever been folded. It's the top
hardware level of the page tables and always has been.
I really do think this series is changing things, not keeping them the same.
next prev parent reply other threads:[~2026-07-13 17:57 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-13 13:55 [RFC PATCH 00/34] mm: optimize unnecessary loads due to ptep_get() and friends out Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 01/34] ARM: mm: make nommu pgd_t a scalar Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 02/34] ARM: mm: make 2-level " Yeoreum Yun
2026-07-13 15:38 ` Arnd Bergmann
2026-07-13 16:04 ` David Hildenbrand (Arm)
2026-07-13 16:26 ` David Hildenbrand (Arm)
2026-07-14 10:26 ` Pedro Falcato
2026-07-14 10:54 ` David Hildenbrand (Arm)
2026-07-14 11:55 ` Arnd Bergmann
2026-07-14 13:34 ` David Laight
2026-07-14 15:06 ` Arnd Bergmann
2026-07-14 12:34 ` David Laight
2026-07-14 13:03 ` David Hildenbrand (Arm)
2026-07-13 13:55 ` [RFC PATCH 03/34] ARM: mm: remove custom pgdp_get() Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 04/34] LoongArch: mm: define pud_leaf() only when PUD exists Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 05/34] MIPS: " Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 06/34] mm/pgtable: define (pgd|p4d|pud)_leaf() for folded page tables Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 07/34] mm/pgtable: define (pgd|p4d|pud)_offset_lockless() " Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 08/34] loongarch: kvm: remove stack copy address of pXd in pXd_offset() Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 09/34] riscv: " Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 10/34] x86: mm: carve out the generic compile-time folded pgtable case in effective_prot() Yeoreum Yun
2026-07-13 14:19 ` Dave Hansen
2026-07-13 14:41 ` David Hildenbrand (Arm)
2026-07-13 14:55 ` Dave Hansen
2026-07-13 15:02 ` David Hildenbrand (Arm)
2026-07-13 17:57 ` Dave Hansen [this message]
2026-07-13 19:49 ` David Hildenbrand (Arm)
2026-07-13 20:27 ` Dave Hansen
2026-07-13 21:17 ` David Hildenbrand (Arm)
2026-07-13 21:40 ` Dave Hansen
2026-07-14 10:50 ` David Hildenbrand (Arm)
2026-07-14 11:40 ` Yeoreum Yun
2026-07-14 14:35 ` Dave Hansen
2026-07-14 16:08 ` Yeoreum Yun
2026-07-14 16:31 ` David Hildenbrand (Arm)
2026-07-14 16:51 ` Yeoreum Yun
2026-07-14 17:29 ` David Hildenbrand (Arm)
2026-07-13 14:48 ` Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 11/34] mm: vmscan: remove stack copy address of pud pass in wallk_pud_range() Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 12/34] arm64: mm: use proper set_pXd() for generic compile-time folded patable in kasan_early_init() Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 13/34] arm64: mm: define pud_set_huge() when __PGTABLE_PMD_FOLDED not defined Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 14/34] csky: mm: use proper set_pXd() for generic compile-time folded patable in vmalloc_fault() Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 15/34] mips: mm: use proper set_pXd() for generic compile-time folded patable in vmalloc_fault path Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 16/34] nios2: " Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 17/34] riscv: mm: use proper set_pXd() for generic compile-time folded patable in vmalloc_fault() Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 18/34] riscv: mm: use proper set_pXd() for generic compile-time folded patable in setup_vm_final() Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 19/34] x86: power: use proper set_pXd() for generic compile-time folded patable in resume_one_md_table_init() Yeoreum Yun
2026-07-13 14:38 ` Dave Hansen
2026-07-13 14:59 ` David Hildenbrand (Arm)
2026-07-13 15:01 ` Yeoreum Yun
2026-07-13 13:55 ` [RFC PATCH 20/34] x86: kexec: use proper set_pXd() for generic compile-time folded patable in machine_kexec_page_table_set_one() Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 21/34] x86: platform: use proper set_pXd() for generic compile-time folded patable in setup_olpc_ofw_pgd() Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 22/34] x86: mm: use proper set_pXd() for generic compile-time folded patable in one_md_table_init() Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 23/34] x86: mm: skip pud setup when using generic compile-time folded pagetable Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 24/34] x86: mm: call try_to_free_pmd_page() when CONFIG_PGTABLE_LEVELS > 2 Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 25/34] x86: mm: remove usage of pgd_page_vaddr() for CONFIG_x86_PAE Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 26/34] x86: mm: define pudp_set_access_flags() when CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD is enabled only Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 27/34] m68k: mm: remove usage of pgd_page_vaddr() for CONFIG_PGTABLE_LEVELS=3 Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 28/34] arm: mm: use proper pgtable APIs for generic compile-time folded patable in kasan_init() Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 29/34] mm/pgtable: disallow calling folded set_pgd/set_p4d/set_pud Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 30/34] mm/pgtable: disallow calling folded (pgd|p4d|pud)_page, pgd_page_vaddr() and (p4d|pud)_pgtable Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 31/34] mm/pgtable: optimize pmdp_get() and friends for folded pagetable levels Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 32/34] openrisc/pgtable: drop __pmd_offset() Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 33/34] mm/pgtable: catch abuse of folded dummy pgd_t/p4d_t/pud_t Yeoreum Yun
2026-07-13 13:56 ` [RFC PATCH 34/34] arm64: pgtable: convert pte_present() from macro to static inline Yeoreum Yun
2026-07-13 14:08 ` [RFC PATCH 00/34] mm: optimize unnecessary loads due to ptep_get() and friends out David Hildenbrand (Arm)
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