This addition will be necessary for some HVF related work to follow.
For HVF on ARM there exists a set of APIs in macOS 13 to be able to
adjust the IPA size for a given VM. This is useful as by default HVF
uses 36 bits as the IPA size, so to support guests with > 64GB of RAM
we'll need to reach for this.

To have all the info necessary to carry this out however, we need some
plumbing to be able to grab the memory map and compute the highest GPA
prior to creating the VM. This is almost exactly like what kvm_type is
used for on ARM today, and is also what this will be used for. We will
compute the highest GPA and find what IPA size we'd need to satisfy this,
and if it's valid (macOS today caps at 40b) we'll set this to be the IPA
size in coming patches. This new method is only needed (today at least)
on ARM, and obviously only for HVF/macOS, so admittedly it is much less
generic than kvm_type today, but it seemed a somewhat sane way to get
the information we need from the memmap at VM creation time.

Signed-off-by: Danny Canter <danny_canter@apple.com>
---
 hw/arm/virt.c       | 9 ++++++++-
 hw/i386/x86.c       | 2 ++
 include/hw/boards.h | 5 +++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 687fe0bb8b..62ee5f849b 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2107,7 +2107,8 @@ static void machvirt_init(MachineState *machine)
 
     /*
      * In accelerated mode, the memory map is computed earlier in kvm_type()
-     * to create a VM with the right number of IPA bits.
+     * for Linux, or hvf_get_physical_address_range() for macOS to create a
+     * VM with the right number of IPA bits.
      */
     if (!vms->memmap) {
         Object *cpuobj;
@@ -3027,6 +3028,11 @@ static int virt_kvm_type(MachineState *ms, const char *type_str)
     return fixed_ipa ? 0 : requested_pa_size;
 }
 
+static int virt_hvf_get_physical_address_range(MachineState *ms)
+{
+    return 0;
+}
+
 static void virt_machine_class_init(ObjectClass *oc, void *data)
 {
     MachineClass *mc = MACHINE_CLASS(oc);
@@ -3086,6 +3092,7 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
     mc->valid_cpu_types = valid_cpu_types;
     mc->get_default_cpu_node_id = virt_get_default_cpu_node_id;
     mc->kvm_type = virt_kvm_type;
+    mc->hvf_get_physical_address_range = virt_hvf_get_physical_address_range;
     assert(!mc->get_hotplug_handler);
     mc->get_hotplug_handler = virt_machine_get_hotplug_handler;
     hc->pre_plug = virt_machine_device_pre_plug_cb;
diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index 01fc5e6562..fa7a0f6b98 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -382,6 +382,8 @@ static void x86_machine_class_init(ObjectClass *oc, void *data)
     mc->get_default_cpu_node_id = x86_get_default_cpu_node_id;
     mc->possible_cpu_arch_ids = x86_possible_cpu_arch_ids;
     mc->kvm_type = x86_kvm_type;
+    /* Not needed for x86 */
+    mc->hvf_get_physical_address_range = NULL;
     x86mc->save_tsc_khz = true;
     x86mc->fwcfg_dma_enabled = true;
     nc->nmi_monitor_handler = x86_nmi;
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 48ff6d8b93..bfc7cc7f90 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -215,6 +215,10 @@ typedef struct {
  *    Return the type of KVM corresponding to the kvm-type string option or
  *    computed based on other criteria such as the host kernel capabilities.
  *    kvm-type may be NULL if it is not needed.
+ * @hvf_get_physical_address_range:
+ *    Returns the physical address range in bits to use for the HVF virtual
+ *    machine based on the current boards memory map. This may be NULL if it
+ *    is not needed.
  * @numa_mem_supported:
  *    true if '--numa node.mem' option is supported and false otherwise
  * @hotplug_allowed:
@@ -256,6 +260,7 @@ struct MachineClass {
     void (*reset)(MachineState *state, ShutdownCause reason);
     void (*wakeup)(MachineState *state);
     int (*kvm_type)(MachineState *machine, const char *arg);
+    int (*hvf_get_physical_address_range)(MachineState *machine);
 
     BlockInterfaceType block_default_type;
     int units_per_default_bus;
-- 
2.39.5 (Apple Git-154)

On Wed, 28 Aug 2024 at 12:16, Danny Canter <danny_canter@apple.com> wrote:
>
> This addition will be necessary for some HVF related work to follow.
> For HVF on ARM there exists a set of APIs in macOS 13 to be able to
> adjust the IPA size for a given VM. This is useful as by default HVF
> uses 36 bits as the IPA size, so to support guests with > 64GB of RAM
> we'll need to reach for this.
>
> To have all the info necessary to carry this out however, we need some
> plumbing to be able to grab the memory map and compute the highest GPA
> prior to creating the VM. This is almost exactly like what kvm_type is
> used for on ARM today, and is also what this will be used for. We will
> compute the highest GPA and find what IPA size we'd need to satisfy this,
> and if it's valid (macOS today caps at 40b) we'll set this to be the IPA
> size in coming patches. This new method is only needed (today at least)
> on ARM, and obviously only for HVF/macOS, so admittedly it is much less
> generic than kvm_type today, but it seemed a somewhat sane way to get
> the information we need from the memmap at VM creation time.
>
> Signed-off-by: Danny Canter <danny_canter@apple.com>

> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> index 01fc5e6562..fa7a0f6b98 100644
> --- a/hw/i386/x86.c
> +++ b/hw/i386/x86.c
> @@ -382,6 +382,8 @@ static void x86_machine_class_init(ObjectClass *oc, void *data)
>      mc->get_default_cpu_node_id = x86_get_default_cpu_node_id;
>      mc->possible_cpu_arch_ids = x86_possible_cpu_arch_ids;
>      mc->kvm_type = x86_kvm_type;
> +    /* Not needed for x86 */
> +    mc->hvf_get_physical_address_range = NULL;
>      x86mc->save_tsc_khz = true;
>      x86mc->fwcfg_dma_enabled = true;
>      nc->nmi_monitor_handler = x86_nmi;

We guarantee that object and class structs are zero-initialized,
so we don't need to explicitly set this field to NULL.

Otherwise
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM