[PATCH 2/5] arm: qemu: enable LPAE on 32-bit

[Heinrich Schuchardt]

On 6/6/20 10:32 PM, Heinrich Schuchardt wrote:
> On 6/6/20 7:15 PM, Ard Biesheuvel wrote:
>> QEMU's mach-virt machine only supports selecting CPU models that
>> implement the virtualization extensions, and are therefore guaranteed
>> to support LPAE as well.
>
> I wonder why
> qemu-system-arm -machine virt -cpu help
> lists cortex-a9 (which is not LPAE enabled).
>
> But when I try to use it I get
> qemu-system-arm: mach-virt: CPU type cortex-a9-arm-cpu not supported
> This looks like a missing feature in QEMU.
>
> The default CPU for machine=virt is arm,cortex-a15.
>
> Acked-by: Heinrich Schuchardt <xypron.glpk at gmx.de.
>
>>
>> Initially, QEMU would not allow emulating these CPUs running in HYP
>> mode (or EL2, for AArch64), but today, it also contains a complete
>> implementation of the virtualization extensions themselves.
>>
>> This means we could be running U-Boot in HYP mode, in which case the
>> LPAE long descriptor page table format is the only format that is
>> supported. If we are not running in HYP mode, we can use either.
>>
>> So let's enable CONFIG_ARMV7_LPAE for qemu_arm_defconfig so that we
>> get the best support for running with the MMU and caches enabled at
>> any privilege level.
>>
>> Signed-off-by: Ard Biesheuvel <ardb at kernel.org>

You missed to CC the maintainer of QEMU ARM 'VIRT' BOARD. - We have
scripts/get_maintainer.pl to find the maintainers.

Cc: Tuomas Tynkkynen <tuomas.tynkkynen at iki.fi>

Best regards

Heinrich

>> ---
>>  configs/qemu_arm_defconfig | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/configs/qemu_arm_defconfig b/configs/qemu_arm_defconfig
>> index a8473988bd76..75bdce7708c7 100644
>> --- a/configs/qemu_arm_defconfig
>> +++ b/configs/qemu_arm_defconfig
>> @@ -1,5 +1,6 @@
>>  CONFIG_ARM=y
>>  CONFIG_ARM_SMCCC=y
>> +CONFIG_ARMV7_LPAE=y
>>  CONFIG_ARCH_QEMU=y
>>  CONFIG_ENV_SIZE=0x40000
>>  CONFIG_ENV_SECT_SIZE=0x40000
>>