[RFC v3 17/24] hw/arm/virt: Reserve one bit of guest physical address for RME

From: Jean-Philippe Brucker <[email protected]>

When RME is enabled, the upper GPA bit is used to distinguish protected
from unprotected addresses. Reserve it when setting up the guest memory
map.

Signed-off-by: Jean-Philippe Brucker <[email protected]>
Signed-off-by: Mathieu Poirier <[email protected]>
---
 hw/arm/virt.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index fe195d145676..2132e6595baf 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -3972,17 +3972,27 @@ static int virt_kvm_type(MachineState *ms, const char *type_str)
 {
     VirtMachineState *vms = VIRT_MACHINE(ms);
     int max_vm_pa_size, requested_pa_size;
+    int rme_reserve_bit = 0;
     bool fixed_ipa;
     int vm_type;
 
-    max_vm_pa_size = kvm_arm_get_max_vm_ipa_size(ms, &fixed_ipa);
-
     vm_type = (ms->cgs ? KVM_VM_TYPE_ARM_REALM : KVM_VM_TYPE_ARM_NORMAL);
 
+    if (vm_type) {
+        /*
+         * With RME, the upper GPA bit differentiates Realm from NS memory.
+         * Reserve the upper bit to ensure that highmem devices will fit.
+         */
+        rme_reserve_bit = 1;
+    }
+
+    max_vm_pa_size = kvm_arm_get_max_vm_ipa_size(ms, &fixed_ipa) -
+                     rme_reserve_bit;
+
     /* we freeze the memory map to compute the highest gpa */
     virt_set_memmap(vms, max_vm_pa_size);
 
-    requested_pa_size = 64 - clz64(vms->highest_gpa);
+    requested_pa_size = 64 - clz64(vms->highest_gpa) + rme_reserve_bit;
 
     /*
      * KVM requires the IPA size to be at least 32 bits.
@@ -3991,11 +4001,11 @@ static int virt_kvm_type(MachineState *ms, const char *type_str)
         requested_pa_size = 32;
     }
 
-    if (requested_pa_size > max_vm_pa_size) {
+    if (requested_pa_size > max_vm_pa_size + rme_reserve_bit) {
         error_report("-m and ,maxmem option values "
                      "require an IPA range (%d bits) larger than "
                      "the one supported by the host (%d bits)",
-                     requested_pa_size, max_vm_pa_size);
+                     requested_pa_size, max_vm_pa_size + rme_reserve_bit);
         return -1;
     }
     /*
-- 
2.43.0