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SubjectRe: [kvmtool test PATCH 22/24] kvmtool: arm64: Add support for guest physical address size
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Hi,

On 04/07/18 15:09, Will Deacon wrote:
> On Fri, Jun 29, 2018 at 12:15:42PM +0100, Suzuki K Poulose wrote:
>> Add an option to specify the physical address size used by this
>> VM.
>>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>> ---
>> arm/aarch64/include/kvm/kvm-config-arch.h | 5 ++++-
>> arm/include/arm-common/kvm-config-arch.h | 1 +
>> 2 files changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/arm/aarch64/include/kvm/kvm-config-arch.h b/arm/aarch64/include/kvm/kvm-config-arch.h
>> index 04be43d..dabd22c 100644
>> --- a/arm/aarch64/include/kvm/kvm-config-arch.h
>> +++ b/arm/aarch64/include/kvm/kvm-config-arch.h
>> @@ -8,7 +8,10 @@
>> "Create PMUv3 device"), \
>> OPT_U64('\0', "kaslr-seed", &(cfg)->kaslr_seed, \
>> "Specify random seed for Kernel Address Space " \
>> - "Layout Randomization (KASLR)"),
>> + "Layout Randomization (KASLR)"), \
>> + OPT_INTEGER('\0', "phys-shift", &(cfg)->phys_shift, \
>> + "Specify maximum physical address size (not " \
>> + "the amount of memory)"),
>
> Given that this is a shift value, I think the help message could be more
> informative. Something like:
>
> "Specify maximum number of bits in a guest physical address"
>
> I think I'd actually leave out any mention of memory, because this does
> actually have an effect on the amount of addressable memory in a way that I
> don't think we want to describe in half of a usage message line :)
Is there any particular reasons to expose this option to the user?

I have recently sent a series to allow the user to specify the position
of the RAM [1]. With that series in mind, I think the user would not
really need to specify the maximum physical shift. Instead we could
automatically find it.

Cheers,

[1]
http://archive.armlinux.org.uk/lurker/message/20180510.140428.1c295b5b.en.html

>
> Will
>

--
Julien Grall

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