Re: [PATCH v2 0/3] hvf: arm: Support creating VMs with 64+GB of RAM on macOS 15+

[Peter Maydell]

On Wed, 28 Aug 2024 at 12:16, Danny Canter <danny_canter@apple.com> wrote:
>
> This patchsets focus is on lighting up the ability to create VMs with 64+GB
> of RAM through using some new APIs introduced in macOS 13. Due to the IPA 
> sizes
> supported in macOS, the first version we can properly support this requirement
> is macOS 15 as (if the hardware supports it also) the kernel adds support for 
> a
> 40b IPA size, which is the first supported ARM PARange value after 36b, so we
> can advertise this to the guest properly as well in id_aa64mmfr0_el1.
>
> Today if you asked for a > 64GB VM you'd be met with a pretty unwieldy
> HV_BAD_ARGUMENT. On machines without 40b IPA support this patchset also
> improves this, and the message mirrors the kvm_type error you'd get on ARM:
>
> "qemu-system-aarch64: -accel hvf: Addressing limited to 36 bits, but memory
> exceeds it by 18253611008 bytes"
>
> Changes from V1 to V2 (Thanks Peter for review!):
>
> - Added a new function pointer to MachineClass to be able to freeze the memory
> map and compute the highest guest physical address. We use this to inform VM
> creation on what IPA size we should ask the kernel for. This is very similar 
> to
> what ARM's kvm_type() does.
>
> - Fixed redundant loop in `round_down_to_parange_bit_size`
>
> - Move the splitting up of hv_vm_create logic per platform to a separate 
> patch.
> This is mostly for readability.

I only had one minor comment on patch 1, so I've applied the
series to target-arm.next and made that tweak there.

thanks
-- PMM