Re: [Qemu-devel] [kvmtool test PATCH 22/24] kvmtool: arm64: Add support for guest physical address size

[Will Deacon <will.deacon@arm.com>]

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 :)

Will