[PATCH v4 4/6] hw/arm/virt: Use the PA range to compute the memory map

[Marc Zyngier <maz@kernel.org>]

The highmem attribute is nothing but another way to express the
PA range of a VM. To support HW that has a smaller PA range then
what QEMU assumes, pass this PA range to the virt_set_memmap()
function, allowing it to correctly exclude highmem devices
if they are outside of the PA range.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 hw/arm/virt.c | 53 ++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 46 insertions(+), 7 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 57c55e8a37..db4b0636e1 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1660,7 +1660,7 @@ static uint64_t virt_cpu_mp_affinity(VirtMachineState *vms, int idx)
     return arm_cpu_mp_affinity(idx, clustersz);
 }
 
-static void virt_set_memmap(VirtMachineState *vms)
+static void virt_set_memmap(VirtMachineState *vms, int pa_bits)
 {
     MachineState *ms = MACHINE(vms);
     hwaddr base, device_memory_base, device_memory_size, memtop;
@@ -1678,6 +1678,13 @@ static void virt_set_memmap(VirtMachineState *vms)
         exit(EXIT_FAILURE);
     }
 
+    /*
+     * !highmem is exactly the same as limiting the PA space to 32bit,
+     * irrespective of the underlying capabilities of the HW.
+     */
+    if (!vms->highmem)
+	    pa_bits = 32;
+
     /*
      * We compute the base of the high IO region depending on the
      * amount of initial and device memory. The device memory start/size
@@ -1691,8 +1698,9 @@ static void virt_set_memmap(VirtMachineState *vms)
 
     /* Base address of the high IO region */
     memtop = base = device_memory_base + ROUND_UP(device_memory_size, GiB);
-    if (!vms->highmem && memtop > 4 * GiB) {
-        error_report("highmem=off, but memory crosses the 4GiB limit\n");
+    if (memtop > BIT_ULL(pa_bits)) {
+	    error_report("Addressing limited to %d bits, but memory exceeds it by %llu bytes\n",
+			 pa_bits, memtop - BIT_ULL(pa_bits));
         exit(EXIT_FAILURE);
     }
     if (base < device_memory_base) {
@@ -1711,7 +1719,13 @@ static void virt_set_memmap(VirtMachineState *vms)
         vms->memmap[i].size = size;
         base += size;
     }
-    vms->highest_gpa = (vms->highmem ? base : memtop) - 1;
+
+    /*
+     * If base fits within pa_bits, all good. If it doesn't, limit it
+     * to the end of RAM, which is guaranteed to fit within pa_bits.
+     */
+    vms->highest_gpa = (base <= BIT_ULL(pa_bits) ? base : memtop) - 1;
+
     if (device_memory_size > 0) {
         ms->device_memory = g_malloc0(sizeof(*ms->device_memory));
         ms->device_memory->base = device_memory_base;
@@ -1902,12 +1916,38 @@ static void machvirt_init(MachineState *machine)
     unsigned int smp_cpus = machine->smp.cpus;
     unsigned int max_cpus = machine->smp.max_cpus;
 
+    possible_cpus = mc->possible_cpu_arch_ids(machine);
+
     /*
      * In accelerated mode, the memory map is computed earlier in kvm_type()
      * to create a VM with the right number of IPA bits.
      */
     if (!vms->memmap) {
-        virt_set_memmap(vms);
+        Object *cpuobj;
+        ARMCPU *armcpu;
+        int pa_bits;
+
+        /*
+         * Instanciate a temporary CPU object to find out about what
+         * we are about to deal with. Once this is done, get rid of
+         * the object.
+         */
+        cpuobj = object_new(possible_cpus->cpus[0].type);
+        armcpu = ARM_CPU(cpuobj);
+
+        if (object_property_get_bool(cpuobj, "aarch64", NULL)) {
+            pa_bits = arm_pamax(armcpu);
+        } else if (arm_feature(&armcpu->env, ARM_FEATURE_LPAE)) {
+            /* v7 with LPAE */
+            pa_bits = 40;
+        } else {
+            /* Anything else */
+            pa_bits = 32;
+        }
+
+        object_unref(cpuobj);
+
+        virt_set_memmap(vms, pa_bits);
     }
 
     /* We can probe only here because during property set
@@ -1989,7 +2029,6 @@ static void machvirt_init(MachineState *machine)
 
     create_fdt(vms);
 
-    possible_cpus = mc->possible_cpu_arch_ids(machine);
     assert(possible_cpus->len == max_cpus);
     for (n = 0; n < possible_cpus->len; n++) {
         Object *cpuobj;
@@ -2646,7 +2685,7 @@ static int virt_kvm_type(MachineState *ms, const char *type_str)
     max_vm_pa_size = kvm_arm_get_max_vm_ipa_size(ms, &fixed_ipa);
 
     /* we freeze the memory map to compute the highest gpa */
-    virt_set_memmap(vms);
+    virt_set_memmap(vms, max_vm_pa_size);
 
     requested_pa_size = 64 - clz64(vms->highest_gpa);
 
-- 
2.30.2