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Date:   Mon, 15 Apr 2019 10:58:21 +1000
From:   Oliver <oohall@...il.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Linux MM <linux-mm@...ck.org>,
        Dan Williams <dan.j.williams@...el.com>, ira.weiny@...el.com,
        Jérôme Glisse <jglisse@...hat.com>,
        ohall@...il.com, x86@...nel.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        anshuman.khandual@....com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH 3/3] mm: introduce ARCH_HAS_PTE_DEVMAP

On Sat, Apr 13, 2019 at 4:57 AM Robin Murphy <robin.murphy@....com> wrote:
>
> ARCH_HAS_ZONE_DEVICE is somewhat meaningless in itself, and combined
> with the long-out-of-date comment can lead to the impression than an
> architecture may just enable it (since __add_pages() now "comprehends
> device memory" for itself) and expect things to work.

Good cleanup. ARCH_HAS_ZONE_DEVICE made sense at the time, but it
probably should have been renamed after the memory hotplug rework.

+cc mpe since he does the merging, and

Acked-by: Oliver O'Halloran <oohall@...il.com>

> In practice, however, ZONE_DEVICE users have little chance of
> functioning correctly without __HAVE_ARCH_PTE_DEVMAP, so let's clean
> that up the same way as ARCH_HAS_PTE_SPECIAL and make it the proper
> dependency so the real situation is clearer.
>
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---
>  arch/powerpc/Kconfig                         | 2 +-
>  arch/powerpc/include/asm/book3s/64/pgtable.h | 1 -
>  arch/x86/Kconfig                             | 2 +-
>  arch/x86/include/asm/pgtable.h               | 4 ++--
>  arch/x86/include/asm/pgtable_types.h         | 1 -
>  include/linux/mm.h                           | 4 ++--
>  include/linux/pfn_t.h                        | 4 ++--
>  mm/Kconfig                                   | 5 ++---
>  mm/gup.c                                     | 2 +-
>  9 files changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 5e3d0853c31d..77e1993bba80 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -135,6 +135,7 @@ config PPC
>         select ARCH_HAS_MMIOWB                  if PPC64
>         select ARCH_HAS_PHYS_TO_DMA
>         select ARCH_HAS_PMEM_API                if PPC64
> +       select ARCH_HAS_PTE_DEVMAP              if PPC_BOOK3S_64
>         select ARCH_HAS_PTE_SPECIAL
>         select ARCH_HAS_MEMBARRIER_CALLBACKS
>         select ARCH_HAS_SCALED_CPUTIME          if VIRT_CPU_ACCOUNTING_NATIVE && PPC64
> @@ -142,7 +143,6 @@ config PPC
>         select ARCH_HAS_TICK_BROADCAST          if GENERIC_CLOCKEVENTS_BROADCAST
>         select ARCH_HAS_UACCESS_FLUSHCACHE      if PPC64
>         select ARCH_HAS_UBSAN_SANITIZE_ALL
> -       select ARCH_HAS_ZONE_DEVICE             if PPC_BOOK3S_64
>         select ARCH_HAVE_NMI_SAFE_CMPXCHG
>         select ARCH_MIGHT_HAVE_PC_PARPORT
>         select ARCH_MIGHT_HAVE_PC_SERIO
> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index 581f91be9dd4..02c22ac8f387 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -90,7 +90,6 @@
>  #define _PAGE_SOFT_DIRTY       _RPAGE_SW3 /* software: software dirty tracking */
>  #define _PAGE_SPECIAL          _RPAGE_SW2 /* software: special page */
>  #define _PAGE_DEVMAP           _RPAGE_SW1 /* software: ZONE_DEVICE page */
> -#define __HAVE_ARCH_PTE_DEVMAP
>
>  /*
>   * Drivers request for cache inhibited pte mapping using _PAGE_NO_CACHE
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 5ad92419be19..ffd50f27f395 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -60,6 +60,7 @@ config X86
>         select ARCH_HAS_KCOV                    if X86_64
>         select ARCH_HAS_MEMBARRIER_SYNC_CORE
>         select ARCH_HAS_PMEM_API                if X86_64
> +       select ARCH_HAS_PTE_DEVMAP              if X86_64
>         select ARCH_HAS_PTE_SPECIAL
>         select ARCH_HAS_REFCOUNT
>         select ARCH_HAS_UACCESS_FLUSHCACHE      if X86_64
> @@ -69,7 +70,6 @@ config X86
>         select ARCH_HAS_STRICT_MODULE_RWX
>         select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
>         select ARCH_HAS_UBSAN_SANITIZE_ALL
> -       select ARCH_HAS_ZONE_DEVICE             if X86_64
>         select ARCH_HAVE_NMI_SAFE_CMPXCHG
>         select ARCH_MIGHT_HAVE_ACPI_PDC         if ACPI
>         select ARCH_MIGHT_HAVE_PC_PARPORT
> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
> index 2779ace16d23..89a1f6fd48bf 100644
> --- a/arch/x86/include/asm/pgtable.h
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -254,7 +254,7 @@ static inline int has_transparent_hugepage(void)
>         return boot_cpu_has(X86_FEATURE_PSE);
>  }
>
> -#ifdef __HAVE_ARCH_PTE_DEVMAP
> +#ifdef CONFIG_ARCH_HAS_PTE_DEVMAP
>  static inline int pmd_devmap(pmd_t pmd)
>  {
>         return !!(pmd_val(pmd) & _PAGE_DEVMAP);
> @@ -715,7 +715,7 @@ static inline int pte_present(pte_t a)
>         return pte_flags(a) & (_PAGE_PRESENT | _PAGE_PROTNONE);
>  }
>
> -#ifdef __HAVE_ARCH_PTE_DEVMAP
> +#ifdef CONFIG_ARCH_HAS_PTE_DEVMAP
>  static inline int pte_devmap(pte_t a)
>  {
>         return (pte_flags(a) & _PAGE_DEVMAP) == _PAGE_DEVMAP;
> diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
> index d6ff0bbdb394..b5e49e6bac63 100644
> --- a/arch/x86/include/asm/pgtable_types.h
> +++ b/arch/x86/include/asm/pgtable_types.h
> @@ -103,7 +103,6 @@
>  #if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
>  #define _PAGE_NX       (_AT(pteval_t, 1) << _PAGE_BIT_NX)
>  #define _PAGE_DEVMAP   (_AT(u64, 1) << _PAGE_BIT_DEVMAP)
> -#define __HAVE_ARCH_PTE_DEVMAP
>  #else
>  #define _PAGE_NX       (_AT(pteval_t, 0))
>  #define _PAGE_DEVMAP   (_AT(pteval_t, 0))
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index d76dfb7ac617..fe05c94f23e9 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -504,7 +504,7 @@ struct inode;
>  #define page_private(page)             ((page)->private)
>  #define set_page_private(page, v)      ((page)->private = (v))
>
> -#if !defined(__HAVE_ARCH_PTE_DEVMAP) || !defined(CONFIG_TRANSPARENT_HUGEPAGE)
> +#if !defined(CONFIG_ARCH_HAS_PTE_DEVMAP) || !defined(CONFIG_TRANSPARENT_HUGEPAGE)
>  static inline int pmd_devmap(pmd_t pmd)
>  {
>         return 0;
> @@ -1698,7 +1698,7 @@ static inline void sync_mm_rss(struct mm_struct *mm)
>  }
>  #endif
>
> -#ifndef __HAVE_ARCH_PTE_DEVMAP
> +#ifndef CONFIG_ARCH_HAS_PTE_DEVMAP
>  static inline int pte_devmap(pte_t pte)
>  {
>         return 0;
> diff --git a/include/linux/pfn_t.h b/include/linux/pfn_t.h
> index 7bb77850c65a..de8bc66b10a4 100644
> --- a/include/linux/pfn_t.h
> +++ b/include/linux/pfn_t.h
> @@ -104,7 +104,7 @@ static inline pud_t pfn_t_pud(pfn_t pfn, pgprot_t pgprot)
>  #endif
>  #endif
>
> -#ifdef __HAVE_ARCH_PTE_DEVMAP
> +#ifdef CONFIG_ARCH_HAS_PTE_DEVMAP
>  static inline bool pfn_t_devmap(pfn_t pfn)
>  {
>         const u64 flags = PFN_DEV|PFN_MAP;
> @@ -122,7 +122,7 @@ pmd_t pmd_mkdevmap(pmd_t pmd);
>         defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
>  pud_t pud_mkdevmap(pud_t pud);
>  #endif
> -#endif /* __HAVE_ARCH_PTE_DEVMAP */
> +#endif /* CONFIG_ARCH_HAS_PTE_DEVMAP */
>
>  #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
>  static inline bool pfn_t_special(pfn_t pfn)
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 25c71eb8a7db..fcb7ab08e294 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -655,8 +655,7 @@ config IDLE_PAGE_TRACKING
>           See Documentation/admin-guide/mm/idle_page_tracking.rst for
>           more details.
>
> -# arch_add_memory() comprehends device memory
> -config ARCH_HAS_ZONE_DEVICE
> +config ARCH_HAS_PTE_DEVMAP
>         bool
>
>  config ZONE_DEVICE
> @@ -664,7 +663,7 @@ config ZONE_DEVICE
>         depends on MEMORY_HOTPLUG
>         depends on MEMORY_HOTREMOVE
>         depends on SPARSEMEM_VMEMMAP
> -       depends on ARCH_HAS_ZONE_DEVICE
> +       depends on ARCH_HAS_PTE_DEVMAP
>         select XARRAY_MULTI
>
>         help
> diff --git a/mm/gup.c b/mm/gup.c
> index f84e22685aaa..72a5c7d1e1a7 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1623,7 +1623,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
>  }
>  #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
>
> -#if defined(__HAVE_ARCH_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
> +#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
>  static int __gup_device_huge(unsigned long pfn, unsigned long addr,
>                 unsigned long end, struct page **pages, int *nr)
>  {
> --
> 2.21.0.dirty
>

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