Re: [PATCH v5 18/18] kvm: arm64: Allow tuning the physical address size for VM

From: Suzuki K Poulose
Date: Mon Sep 17 2018 - 10:44:01 EST

Hi Peter,

On 17/09/2018 15:20, Peter Maydell wrote:
On 17 September 2018 at 11:41, Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
Allow specifying the physical address size limit for a new
VM via the kvm_type argument for the KVM_CREATE_VM ioctl. This
allows us to finalise the stage2 page table as early as possible
and hence perform the right checks on the memory slots
without complication. The size is ecnoded as Log2(PA_Size) in
bits[7:0] of the type field. For backward compatibility the
value 0 is reserved and implies 40bits. Also, lift the limit
of the IPA to host limit and allow lower IPA sizes (e.g, 32).

The userspace could check the extension KVM_CAP_ARM_VM_PHYS_SHIFT
for the availability of this feature. The cap check returns the
maximum limit for the physical address shift supported by the host.

Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Christoffer Dall <cdall@xxxxxxxxxx>
Cc: Peter Maydel <peter.maydell@xxxxxxxxxx>

Typo: my surname has two "l"s in it.

Sorry about that. I have fixed this locally. Btw, did you get
a chance to look at the patch itself ? If you did, are you fine
with the API ?