Re: [PATCH 1/5] ArmPkg/ArmLib: add support for reading the max physical address space size

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

On 26/11/18 12:46, Ard Biesheuvel wrote:
> On Fri, 23 Nov 2018 at 13:14, Ard Biesheuvel <ard.biesheuvel@linaro.org> 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>
>> ---
>>  ArmPkg/Include/Library/ArmLib.h               |  6 ++++++
>>  ArmPkg/Library/ArmLib/AArch64/ArmLibSupport.S | 16 ++++++++++++++++
>>  ArmPkg/Library/ArmLib/Arm/ArmLibSupport.S     |  8 ++++++++
>>  3 files changed, 30 insertions(+)
>>
>> diff --git a/ArmPkg/Include/Library/ArmLib.h b/ArmPkg/Include/Library/ArmLib.h
>> index ffda50e9d767..9a804c15fdb6 100644
>> --- a/ArmPkg/Include/Library/ArmLib.h
>> +++ b/ArmPkg/Include/Library/ArmLib.h
>> @@ -733,4 +733,10 @@ 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..75ab8dade485 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, -1, -1
>> +
> 
> Note: as Drew pointed out, we want 52 bits included as well in this
> enumeration. I will fix that up when applying (unless anyone objects)

Using index 6 == 52 and updating the comment:
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> 
>>  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
>> --
>> 2.17.1
>>