[PATCH v4 3/6] hw/arm/virt: Honor highmem setting when computing the memory map

[Marc Zyngier]

Even when the VM is configured with highmem=off, the highest_gpa
field includes devices that are above the 4GiB limit.
Similarily, nothing seem to check that the memory is within
the limit set by the highmem=off option.

This leads to failures in virt_kvm_type() on systems that have
a crippled IPA range, as the reported IPA space is larger than
what it should be.

Instead, honor the user-specified limit to only use the devices
at the lowest end of the spectrum, and fail if we have memory
crossing the 4GiB limit.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 hw/arm/virt.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 4d1d629432..57c55e8a37 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1663,7 +1663,7 @@ static uint64_t virt_cpu_mp_affinity(VirtMachineState 
*vms, int idx)
 static void virt_set_memmap(VirtMachineState *vms)
 {
     MachineState *ms = MACHINE(vms);
-    hwaddr base, device_memory_base, device_memory_size;
+    hwaddr base, device_memory_base, device_memory_size, memtop;
     int i;
 
     vms->memmap = extended_memmap;
@@ -1690,7 +1690,11 @@ static void virt_set_memmap(VirtMachineState *vms)
     device_memory_size = ms->maxram_size - ms->ram_size + ms->ram_slots * GiB;
 
     /* Base address of the high IO region */
-    base = device_memory_base + ROUND_UP(device_memory_size, GiB);
+    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");
+        exit(EXIT_FAILURE);
+    }
     if (base < device_memory_base) {
         error_report("maxmem/slots too huge");
         exit(EXIT_FAILURE);
@@ -1707,7 +1711,7 @@ static void virt_set_memmap(VirtMachineState *vms)
         vms->memmap[i].size = size;
         base += size;
     }
-    vms->highest_gpa = base - 1;
+    vms->highest_gpa = (vms->highmem ? base : memtop) - 1;
     if (device_memory_size > 0) {
         ms->device_memory = g_malloc0(sizeof(*ms->device_memory));
         ms->device_memory->base = device_memory_base;
-- 
2.30.2