Re: [PATCH v2 2/2] hw/arm/virt: KVM: The IPA lower bound is 32

[Marc Zyngier <maz@kernel.org>]

On Wed, 10 Mar 2021 13:52:18 +0000,
Andrew Jones <drjones@redhat.com> wrote:
> 
> The virt machine already checks KVM_CAP_ARM_VM_IPA_SIZE to get the
> upper bound of the IPA size. If that bound is lower than the highest
> possible GPA for the machine, then QEMU will error out. However, the
> IPA is set to 40 when the highest GPA is less than or equal to 40,
> even when KVM may support an IPA limit as low as 32. This means KVM
> may fail the VM creation unnecessarily. Additionally, 40 is selected
> with the value 0, which means use the default, and that gets around
> a check in some versions of KVM, causing a difficult to debug fail.
> Always use the IPA size that corresponds to the highest possible GPA,
> unless it's lower than 32, in which case use 32. Also, we must still
> use 0 when KVM only supports the legacy fixed 40 bit IPA.
> 
> Suggested-by: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Andrew Jones <drjones@redhat.com>

Reviewed-by: Marc Zyngier <maz@kernel.org>

	M.

-- 
Without deviation from the norm, progress is not possible.