Messages in this thread | | | Subject | Re: [kvmtool test PATCH 22/24] kvmtool: arm64: Add support for guest physical address size | From | Julien Grall <> | Date | Thu, 5 Jul 2018 13:47:26 +0100 |
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Hi Will,
On 04/07/18 16:52, Will Deacon wrote: > On Wed, Jul 04, 2018 at 04:00:11PM +0100, Julien Grall wrote: >> 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. > > Marc makes a good point that it doesn't help for MMIO regions, so I'm trying > to understand whether we can do something differently there and avoid > sacrificing the type parameter.
I am not sure to understand this. kvmtools knows the memory layout (including MMIOs) of the guest, so couldn't it guess the maximum physical shift for that?
Cheers,
-- Julien Grall
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