[PATCH] hw/arm/virt: KVM: The IPA lower bound is 32

[Andrew Jones]

The virt machine already checks KVM_CAP_ARM_VM_IPA_SIZE to get the
upper bound of the IPA size. If that bound is lower than the highest
possible GPA for the machine, then QEMU will error out. However, the
IPA is set to 40 when the highest GPA is less than or equal to 40,
even when KVM may only support an IPA limit as low as 32. This means
KVM may fail the VM creation unnecessarily. Additionally, 40 is
selected with the value 0, which means use the default, and that gets
around a check in some versions of KVM, causing a difficult to debug
fail. Always use the IPA size that corresponds to the highest possible
GPA, unless it's lower than 32, in which case use 32.

Signed-off-by: Andrew Jones <drjones@redhat.com>
---
 hw/arm/virt.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 371147f3ae9c..7bf563715b4e 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2547,14 +2547,13 @@ static int virt_kvm_type(MachineState *ms, const char 
*type_str)
                      "require an IPA range (%d bits) larger than "
                      "the one supported by the host (%d bits)",
                      requested_pa_size, max_vm_pa_size);
-       exit(1);
+        exit(1);
     }
+
     /*
-     * By default we return 0 which corresponds to an implicit legacy
-     * 40b IPA setting. Otherwise we return the actual requested PA
-     * logsize
+     * KVM requires the IPA size to be at least 32 bits.
      */
-    return requested_pa_size > 40 ? requested_pa_size : 0;
+    return requested_pa_size < 32 ? 32 : requested_pa_size;
 }
 
 static void virt_machine_class_init(ObjectClass *oc, void *data)
-- 
2.27.0