Re: [PATCH v2 01/13] ArmPkg/ArmLib: add support for reading the max physical address space size

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 26/11/18 23:37, Ard Biesheuvel wrote:
> Add a helper function that returns the maximum physical address space
> size as supported by the current CPU.
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>  ArmPkg/Include/Library/ArmLib.h               | 17 +++++++++++++++++
>  ArmPkg/Library/ArmLib/AArch64/ArmLibSupport.S | 16 ++++++++++++++++
>  ArmPkg/Library/ArmLib/Arm/ArmLibSupport.S     |  8 ++++++++
>  3 files changed, 41 insertions(+)
> 
> diff --git a/ArmPkg/Include/Library/ArmLib.h b/ArmPkg/Include/Library/ArmLib.h
> index ffda50e9d767..b22879fe6e94 100644
> --- a/ArmPkg/Include/Library/ArmLib.h
> +++ b/ArmPkg/Include/Library/ArmLib.h
> @@ -29,6 +29,17 @@
>  #define EFI_MEMORY_CACHETYPE_MASK   (EFI_MEMORY_UC | EFI_MEMORY_WC | \
>                                       EFI_MEMORY_WT | EFI_MEMORY_WB | \
>                                       EFI_MEMORY_UCE)
> +//
> +// ARM_MMU_IDMAP_RANGE defines the maximum size of the identity mapping
> +// that covers the entire address space when running in UEFI. This is
> +// limited to what can architecturally be mapped using a 4 KB granule,
> +// even if the hardware is capable of mapping more using larger pages.
> +//
> +#ifdef MDE_CPU_ARM
> +#define ARM_MMU_IDMAP_RANGE     (1ULL << 32)
> +#else
> +#define ARM_MMU_IDMAP_RANGE     (1ULL << 48)
> +#endif
>  
>  /**
>   * The UEFI firmware must not use the ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_* attributes.
> @@ -733,4 +744,10 @@ ArmWriteCntvOff (
>    UINT64   Val
>    );
>  
> +UINTN
> +EFIAPI
> +ArmGetPhysicalAddressBits (
> +  VOID
> +  );
> +
>  #endif // __ARM_LIB__
> diff --git a/ArmPkg/Library/ArmLib/AArch64/ArmLibSupport.S b/ArmPkg/Library/ArmLib/AArch64/ArmLibSupport.S
> index 1ef2f61f5979..7332601241aa 100644
> --- a/ArmPkg/Library/ArmLib/AArch64/ArmLibSupport.S
> +++ b/ArmPkg/Library/ArmLib/AArch64/ArmLibSupport.S
> @@ -196,4 +196,20 @@ ASM_FUNC(ArmWriteSctlr)
>  3:msr   sctlr_el3, x0
>  4:ret
>  
> +ASM_FUNC(ArmGetPhysicalAddressBits)
> +  mrs   x0, id_aa64mmfr0_el1
> +  adr   x1, .LPARanges
> +  and   x0, x0, #7
> +  ldrb  w0, [x1, x0]
> +  ret
> +
> +//
> +// Bits 0..2 of the AA64MFR0_EL1 system register encode the size of the
> +// physical address space support on this CPU:
> +// 0 == 32 bits, 1 == 36 bits, etc etc
> +// 6 and 7 are reserved
> +//
> +.LPARanges:
> +  .byte 32, 36, 40, 42, 44, 48, 52, -1
> +
>  ASM_FUNCTION_REMOVE_IF_UNREFERENCED
> diff --git a/ArmPkg/Library/ArmLib/Arm/ArmLibSupport.S b/ArmPkg/Library/ArmLib/Arm/ArmLibSupport.S
> index f2a517671f0a..f2f3c9a25991 100644
> --- a/ArmPkg/Library/ArmLib/Arm/ArmLibSupport.S
> +++ b/ArmPkg/Library/ArmLib/Arm/ArmLibSupport.S
> @@ -165,4 +165,12 @@ ASM_FUNC(ArmWriteCpuActlr)
>    isb
>    bx      lr
>  
> +ASM_FUNC (ArmGetPhysicalAddressBits)
> +  mrc     p15, 0, r0, c0, c1, 4   // MMFR0
> +  and     r0, r0, #0xf            // VMSA [3:0]
> +  cmp     r0, #5                  // >5 implies LPAE support
> +  movlt   r0, #32                 // 32 bits if no LPAE
> +  movge   r0, #40                 // 40 bits if LPAE
> +  bx      lr
> +
>  ASM_FUNCTION_REMOVE_IF_UNREFERENCED
>