Re: [Xen-devel] [PATCH v2 05/41] acpi : add helper function for mapping memory

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Parth,

On 24/05/2015 07:40, Parth Dixit wrote:
>     On 17/05/15 21:03, Parth Dixit wrote:
>      > diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
>      > index 935999e..096e9ef 100644
>      > --- a/xen/arch/arm/Makefile
>      > +++ b/xen/arch/arm/Makefile
>      > @@ -2,6 +2,7 @@ subdir-$(arm32) += arm32
>      >  subdir-$(arm64) += arm64
>      >  subdir-y += platforms
>      >  subdir-$(arm64) += efi
>      > +subdir-$(HAS_ACPI) += acpi
>      >
>      >  obj-$(EARLY_PRINTK) += early_printk.o
>      >  obj-y += cpu.o
>      > diff --git a/xen/arch/arm/acpi/Makefile b/xen/arch/arm/acpi/Makefile
>      > new file mode 100644
>      > index 0000000..b5be22d
>      > --- /dev/null
>      > +++ b/xen/arch/arm/acpi/Makefile
>      > @@ -0,0 +1 @@
>      > +obj-y += lib.o
>      > diff --git a/xen/arch/arm/acpi/lib.c b/xen/arch/arm/acpi/lib.c
>      > new file mode 100644
>      > index 0000000..650beed
>      > --- /dev/null
>      > +++ b/xen/arch/arm/acpi/lib.c
>      > @@ -0,0 +1,8 @@
>      > +#include <xen/acpi.h>
>      > +#include <asm/mm.h>
>      > +
>      > +void __iomem *
>      > +acpi_os_map_iomem(acpi_physical_address phys, acpi_size size)
>      > +{
>      > +    return __va(phys);
>      > +}
>
>     I would have prefer two distinct patch: one for the refactoring of
>     acpi_os_map_memory and the other for implementing the ARM part
>     explaining why only using __va.
>
>     __va should only be used when the memory is direct-mapped to Xen (i.e
>     accessible directly). On ARM64, this only the case for the RAM. Can you
>     confirm that ACPI will always reside to the RAM?
>
>     I already asked the same question on the previous version but got no
>     answer from you...
>
> I did not found any document which says it will always reside in RAM or
> otherwise..
If so, you have use vmap or ioremap_cache as suggested by Jan.

Regards,

--
Julien Grall

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