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

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

On Mon, Nov 26, 2018 at 11:43 PM Philippe Mathieu-Daudé
<philmd@redhat.com> wrote:
>
> 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

Oops the comment is now invalid for the index == 6.

> > +//
> > +.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
> >