From: Geert Uytterhoeven <geert@linux-m68k.org>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
John Hubbard <jhubbard@nvidia.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Yang Shi <shy828301@gmail.com>, Vlastimil Babka <vbabka@suse.cz>,
Nadav Amit <namit@vmware.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Peter Xu <peterx@redhat.com>,
linux-mm@kvack.org, x86@kernel.org, linux-alpha@vger.kernel.org,
linux-snps-arc@lists.infradead.org,
linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org,
linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org,
loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org,
linux-mips@vger.kernel.org, openrisc@lists.librecores.org,
linux-parisc@vger.kernel.org, linuxp
Subject: Re: [PATCH mm-unstable v1 11/26] microblaze/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE
Date: Sun, 26 Feb 2023 21:13:33 +0100 [thread overview]
Message-ID: <CAMuHMdX-FDga8w=pgg1myskEx6wp+oyZifhPPPFnWrc1zW7ZpQ@mail.gmail.com> (raw)
In-Reply-To: <20230113171026.582290-12-david@redhat.com>
Hi David,
On Fri, Jan 13, 2023 at 6:16 PM David Hildenbrand <david@redhat.com> wrote:
> Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit
> from the type. Generic MM currently only uses 5 bits for the type
> (MAX_SWAPFILES_SHIFT), so the stolen bit is effectively unused.
>
> The shift by 2 when converting between PTE and arch-specific swap entry
> makes the swap PTE layout a little bit harder to decipher.
>
> While at it, drop the comment from paulus---copy-and-paste leftover
> from powerpc where we actually have _PAGE_HASHPTE---and mask the type in
> __swp_entry_to_pte() as well.
>
> Cc: Michal Simek <monstr@monstr.eu>
> Signed-off-by: David Hildenbrand <david@redhat.com>
Thanks for your patch, which is now commit b5c88f21531c3457
("microblaze/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE") in
> arch/m68k/include/asm/mcf_pgtable.h | 4 +--
What is this m68k change doing here?
Sorry for not noticing this earlier.
Furthermore, several things below look strange to me...
> arch/microblaze/include/asm/pgtable.h | 45 +++++++++++++++++++++------
> 2 files changed, 37 insertions(+), 12 deletions(-)
>
> diff --git a/arch/m68k/include/asm/mcf_pgtable.h b/arch/m68k/include/asm/mcf_pgtable.h
> index 3f8f4d0e66dd..e573d7b649f7 100644
> --- a/arch/m68k/include/asm/mcf_pgtable.h
> +++ b/arch/m68k/include/asm/mcf_pgtable.h
> @@ -46,8 +46,8 @@
> #define _CACHEMASK040 (~0x060)
> #define _PAGE_GLOBAL040 0x400 /* 68040 global bit, used for kva descs */
>
> -/* We borrow bit 7 to store the exclusive marker in swap PTEs. */
> -#define _PAGE_SWP_EXCLUSIVE 0x080
> +/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
> +#define _PAGE_SWP_EXCLUSIVE CF_PAGE_NOCACHE
CF_PAGE_NOCACHE is 0x80, so this is still bit 7, thus the new comment
is wrong?
>
> /*
> * Externally used page protection values.
> diff --git a/arch/microblaze/include/asm/pgtable.h b/arch/microblaze/include/asm/pgtable.h
> index 42f5988e998b..7e3de54bf426 100644
> --- a/arch/microblaze/include/asm/pgtable.h
> +++ b/arch/microblaze/include/asm/pgtable.h
> @@ -131,10 +131,10 @@ extern pte_t *va_to_pte(unsigned long address);
> * of the 16 available. Bit 24-26 of the TLB are cleared in the TLB
> * miss handler. Bit 27 is PAGE_USER, thus selecting the correct
> * zone.
> - * - PRESENT *must* be in the bottom two bits because swap cache
> - * entries use the top 30 bits. Because 4xx doesn't support SMP
> - * anyway, M is irrelevant so we borrow it for PAGE_PRESENT. Bit 30
> - * is cleared in the TLB miss handler before the TLB entry is loaded.
> + * - PRESENT *must* be in the bottom two bits because swap PTEs use the top
> + * 30 bits. Because 4xx doesn't support SMP anyway, M is irrelevant so we
> + * borrow it for PAGE_PRESENT. Bit 30 is cleared in the TLB miss handler
> + * before the TLB entry is loaded.
So the PowerPC 4xx comment is still here?
> * - All other bits of the PTE are loaded into TLBLO without
> * * modification, leaving us only the bits 20, 21, 24, 25, 26, 30 for
> * software PTE bits. We actually use bits 21, 24, 25, and
> @@ -155,6 +155,9 @@ extern pte_t *va_to_pte(unsigned long address);
> #define _PAGE_ACCESSED 0x400 /* software: R: page referenced */
> #define _PMD_PRESENT PAGE_MASK
>
> +/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
> +#define _PAGE_SWP_EXCLUSIVE _PAGE_DIRTY
_PAGE_DIRTY is 0x80, so this is also bit 7, thus the new comment is
wrong?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
next prev parent reply other threads:[~2023-02-26 20:13 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-13 17:10 [PATCH mm-unstable v1 00/26] mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on all architectures with swap PTEs David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 01/26] mm/debug_vm_pgtable: more pte_swp_exclusive() sanity checks David Hildenbrand
2023-01-14 16:09 ` David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 02/26] alpha/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 03/26] arc/mm: " David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 04/26] arm/mm: " David Hildenbrand
2023-01-13 17:38 ` Russell King (Oracle)
2023-02-07 0:32 ` Mark Brown
2023-02-08 14:12 ` David Hildenbrand
2023-02-08 16:39 ` Mark Brown
2023-01-13 17:10 ` [PATCH mm-unstable v1 05/26] csky/mm: " David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 06/26] hexagon/mm: " David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 07/26] ia64/mm: " David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 08/26] loongarch/mm: " David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 09/26] m68k/mm: remove dummy __swp definitions for nommu David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 10/26] m68k/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 11/26] microblaze/mm: " David Hildenbrand
2023-02-26 20:13 ` Geert Uytterhoeven [this message]
2023-02-27 13:31 ` David Hildenbrand
2023-02-27 14:43 ` Geert Uytterhoeven
2023-02-27 17:01 ` David Hildenbrand
2023-02-27 19:46 ` Geert Uytterhoeven
2023-02-28 15:55 ` David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 12/26] mips/mm: " David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 13/26] nios2/mm: refactor swap PTE layout David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 14/26] nios2/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 15/26] openrisc/mm: " David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 16/26] parisc/mm: " David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 17/26] powerpc/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on 32bit book3s David Hildenbrand
2023-02-10 5:08 ` Michael Ellerman
2023-01-13 17:10 ` [PATCH mm-unstable v1 18/26] powerpc/nohash/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 19/26] riscv/mm: " David Hildenbrand
2023-02-28 15:50 ` Palmer Dabbelt
2023-02-28 15:56 ` David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 20/26] sh/mm: " David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 21/26] sparc/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on 32bit David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 22/26] sparc/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on 64bit David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 23/26] um/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 24/26] x86/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE also on 32bit David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 25/26] xtensa/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE David Hildenbrand
2023-01-13 17:10 ` [PATCH mm-unstable v1 26/26] mm: remove __HAVE_ARCH_PTE_SWP_EXCLUSIVE David Hildenbrand
2023-02-28 21:11 ` [PATCH mm-unstable v1 00/26] mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on all architectures with swap PTEs patchwork-bot+linux-riscv
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