Re: [PATCH] ACPI: Add memory semantics to acpi_os_map_memory()

[Ard Biesheuvel]

On Mon, 26 Jul 2021 at 12:00, Lorenzo Pieralisi
<lorenzo.pieralisi@xxxxxxx> wrote:
>
> The memory attributes attached to memory regions depend on architecture
> specific mappings.
>
> For some memory regions, the attributes specified by firmware (eg
> uncached) are not sufficient to determine how a memory region should be
> mapped by an OS (for instance a region that is define as uncached in
> firmware can be mapped as Normal or Device memory on arm64) and
> therefore the OS must be given control on how to map the region to match
> the expected mapping behaviour (eg if a mapping is requested with memory
> semantics, it must allow unaligned accesses).
>
> Rework acpi_os_map_memory() and acpi_os_ioremap() back-end to split
> them into two separate code paths:
>
> acpi_os_memmap() -> memory semantics
> acpi_os_ioremap() -> MMIO semantics
>
> The split allows the architectural implementation back-ends to detect
> the default memory attributes required by the mapping in question
> (ie the mapping API defines the semantics memory vs MMIO) and map the
> memory accordingly.
>
> Link: https://lore.kernel.org/linux-arm-kernel/31ffe8fc-f5ee-2858-26c5-0fd8bdd68702@xxxxxxx
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Hanjun Guo <guohanjun@xxxxxxxxxx>
> Cc: Sudeep Holla <sudeep.holla@xxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>

For the patch in general

Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>

Couple of nits/questions below

> ---
>  arch/arm64/include/asm/acpi.h |  3 +++
>  arch/arm64/kernel/acpi.c      | 19 ++++++++++++++++---
>  drivers/acpi/osl.c            | 23 ++++++++++++++++-------
>  include/acpi/acpi_io.h        |  8 ++++++++
>  4 files changed, 43 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
> index bd68e1b7f29f..7535dc7cc5aa 100644
> --- a/arch/arm64/include/asm/acpi.h
> +++ b/arch/arm64/include/asm/acpi.h
> @@ -50,6 +50,9 @@ pgprot_t __acpi_get_mem_attribute(phys_addr_t addr);
>  void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size);
>  #define acpi_os_ioremap acpi_os_ioremap
>
> +void __iomem *acpi_os_memmap(acpi_physical_address phys, acpi_size size);
> +#define acpi_os_memmap acpi_os_memmap
> +
>  typedef u64 phys_cpuid_t;
>  #define PHYS_CPUID_INVALID INVALID_HWID
>
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index f3851724fe35..1c9c2f7a1c04 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -273,7 +273,8 @@ pgprot_t __acpi_get_mem_attribute(phys_addr_t addr)
>         return __pgprot(PROT_DEVICE_nGnRnE);
>  }
>
> -void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
> +static void __iomem *__acpi_os_ioremap(acpi_physical_address phys,
> +                                      acpi_size size, bool memory)
>  {
>         efi_memory_desc_t *md, *region = NULL;
>         pgprot_t prot;
> @@ -299,9 +300,11 @@ void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
>          * It is fine for AML to remap regions that are not represented in the
>          * EFI memory map at all, as it only describes normal memory, and MMIO
>          * regions that require a virtual mapping to make them accessible to
> -        * the EFI runtime services.
> +        * the EFI runtime services. Determine the region default
> +        * attributes by checking the requested memory semantics.
>          */
> -       prot = __pgprot(PROT_DEVICE_nGnRnE);
> +       prot = memory ? __pgprot(PROT_NORMAL_NC) :
> +                       __pgprot(PROT_DEVICE_nGnRnE);
>         if (region) {
>                 switch (region->type) {
>                 case EFI_LOADER_CODE:
> @@ -361,6 +364,16 @@ void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
>         return __ioremap(phys, size, prot);
>  }
>
> +void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
> +{
> +       return __acpi_os_ioremap(phys, size, false);
> +}
> +
> +void __iomem *acpi_os_memmap(acpi_physical_address phys, acpi_size size)
> +{
> +       return __acpi_os_ioremap(phys, size, true);
> +}
> +
>  /*
>   * Claim Synchronous External Aborts as a firmware first notification.
>   *
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index 45c5c0e45e33..6db62f3a390e 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -284,7 +284,8 @@ acpi_map_lookup_virt(void __iomem *virt, acpi_size size)
>  #define should_use_kmap(pfn)   page_is_ram(pfn)
>  #endif
>
> -static void __iomem *acpi_map(acpi_physical_address pg_off, unsigned long pg_sz)
> +static void __iomem *acpi_map(acpi_physical_address pg_off, unsigned long pg_sz,
> +                             bool memory)
>  {
>         unsigned long pfn;
>
> @@ -294,7 +295,8 @@ static void __iomem *acpi_map(acpi_physical_address pg_off, unsigned long pg_sz)
>                         return NULL;
>                 return (void __iomem __force *)kmap(pfn_to_page(pfn));
>         } else
> -               return acpi_os_ioremap(pg_off, pg_sz);
> +               return memory ? acpi_os_memmap(pg_off, pg_sz) :
> +                               acpi_os_ioremap(pg_off, pg_sz);
>  }
>
>  static void acpi_unmap(acpi_physical_address pg_off, void __iomem *vaddr)
> @@ -309,9 +311,10 @@ static void acpi_unmap(acpi_physical_address pg_off, void __iomem *vaddr)
>  }
>
>  /**
> - * acpi_os_map_iomem - Get a virtual address for a given physical address range.
> + * __acpi_os_map_iomem - Get a virtual address for a given physical address range.
>   * @phys: Start of the physical address range to map.
>   * @size: Size of the physical address range to map.
> + * @memory: true if remapping memory, false if IO
>   *
>   * Look up the given physical address range in the list of existing ACPI memory
>   * mappings.  If found, get a reference to it and return a pointer to it (its
> @@ -321,8 +324,8 @@ static void acpi_unmap(acpi_physical_address pg_off, void __iomem *vaddr)
>   * During early init (when acpi_permanent_mmap has not been set yet) this
>   * routine simply calls __acpi_map_table() to get the job done.
>   */
> -void __iomem __ref
> -*acpi_os_map_iomem(acpi_physical_address phys, acpi_size size)
> +static void __iomem __ref
> +*__acpi_os_map_iomem(acpi_physical_address phys, acpi_size size, bool memory)
>  {
>         struct acpi_ioremap *map;
>         void __iomem *virt;
> @@ -353,7 +356,7 @@ void __iomem __ref
>
>         pg_off = round_down(phys, PAGE_SIZE);
>         pg_sz = round_up(phys + size, PAGE_SIZE) - pg_off;
> -       virt = acpi_map(phys, size);
> +       virt = acpi_map(phys, size, memory);
>         if (!virt) {
>                 mutex_unlock(&acpi_ioremap_lock);
>                 kfree(map);
> @@ -372,11 +375,17 @@ void __iomem __ref
>         mutex_unlock(&acpi_ioremap_lock);
>         return map->virt + (phys - map->phys);
>  }
> +
> +void __iomem __ref
> +*acpi_os_map_iomem(acpi_physical_address phys, acpi_size size)

I am aware that this just duplicated the prototype above, but I think
this should be

void __iomem *__ref

given that the __ref comes after the * in the prototype below.

> +{
> +       return __acpi_os_map_iomem(phys, size, false);
> +}
>  EXPORT_SYMBOL_GPL(acpi_os_map_iomem);
>
>  void *__ref acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
>  {
> -       return (void *)acpi_os_map_iomem(phys, size);
> +       return (void *)__acpi_os_map_iomem(phys, size, true);

I think this should be (__force void *) to shut up sparse address
space warnings.

>  }
>  EXPORT_SYMBOL_GPL(acpi_os_map_memory);
>
> diff --git a/include/acpi/acpi_io.h b/include/acpi/acpi_io.h
> index 027faa8883aa..a0212e67d6f4 100644
> --- a/include/acpi/acpi_io.h
> +++ b/include/acpi/acpi_io.h
> @@ -14,6 +14,14 @@ static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys,
>  }
>  #endif
>
> +#ifndef acpi_os_memmap
> +static inline void __iomem *acpi_os_memmap(acpi_physical_address phys,
> +                                           acpi_size size)
> +{
> +       return ioremap_cache(phys, size);
> +}
> +#endif
> +
>  extern bool acpi_permanent_mmap;
>
>  void __iomem __ref
> --
> 2.31.0
>