hvf: arm: Implement and use hvf_get_physical_address_range

This patch's main focus is to use the previously added
hvf_get_physical_address_range to inform VM creation
about the IPA size we need for the VM, so we can extend
the default 36b IPA size and support VMs with 64+GB of
RAM. This is done by freezing the memory map, computing
the highest GPA and then (depending on if the platform
supports an IPA size that large) telling the kernel to
use a size >= for the VM. In pursuit of this a couple of
things related to how we handle the physical address range
we expose to guests were altered, but for an explanation of
what we were doing:

Today, to get the IPA size we were reading id_aa64mmfr0_el1's
PARange field from a newly made vcpu. Unfortunately, HVF just
returns the hosts PARange directly for the initial value and
not the IPA size that will actually back the VM, so we believe
we have much more address space than we actually do today it seems.

Starting in macOS 13.0 some APIs were introduced to be able to
query the maximum IPA size the kernel supports, and to set the IPA
size for a given VM. However, this still has a couple of issues
on < macOS 15. Up until macOS 15 (and if the hardware supported
it) the max IPA size was 39 bits which is not a valid PARange
value, so we can't clamp down what we advertise in the vcpu's
id_aa64mmfr0_el1 to our IPA size. Starting in macOS 15 however,
the maximum IPA size is 40 bits (if it's supported in the hardware
as well) which is also a valid PARange value so we can set our IPA
size to the maximum as well as clamp down the PARange we advertise
to the guest. This allows VMs with 64+ GB of RAM and should fix the
oddness of the PARange situation as well.

Signed-off-by: Danny Canter <danny_canter@apple.com>
Message-id: 20240828111552.93482-4-danny_canter@apple.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 30 insertions, 1 deletions

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index d284a602e8..8b2b991d97 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -66,6 +66,7 @@
 #include "hw/intc/arm_gicv3_its_common.h"
 #include "hw/irq.h"
 #include "kvm_arm.h"
+#include "hvf_arm.h"
 #include "hw/firmware/smbios.h"
 #include "qapi/visitor.h"
 #include "qapi/qapi-visit-common.h"
@@ -3034,7 +3035,35 @@ static int virt_kvm_type(MachineState *ms, const char *type_str)
 
 static int virt_hvf_get_physical_address_range(MachineState *ms)
 {
-    return 0;
+    VirtMachineState *vms = VIRT_MACHINE(ms);
+
+    int default_ipa_size = hvf_arm_get_default_ipa_bit_size();
+    int max_ipa_size = hvf_arm_get_max_ipa_bit_size();
+
+    /* We freeze the memory map to compute the highest gpa */
+    virt_set_memmap(vms, max_ipa_size);
+
+    int requested_ipa_size = 64 - clz64(vms->highest_gpa);
+
+    /*
+     * If we're <= the default IPA size just use the default.
+     * If we're above the default but below the maximum, round up to
+     * the maximum. hvf_arm_get_max_ipa_bit_size() conveniently only
+     * returns values that are valid ARM PARange values.
+     */
+    if (requested_ipa_size <= default_ipa_size) {
+        requested_ipa_size = default_ipa_size;
+    } else if (requested_ipa_size <= max_ipa_size) {
+        requested_ipa_size = max_ipa_size;
+    } else {
+        error_report("-m and ,maxmem option values "
+                     "require an IPA range (%d bits) larger than "
+                     "the one supported by the host (%d bits)",
+                     requested_ipa_size, max_ipa_size);
+        return -1;
+    }
+
+    return requested_ipa_size;
 }
 
 static void virt_machine_class_init(ObjectClass *oc, void *data)