[PATCH v2 3/4] hw/arm/virt: Improve address assignment for high memory regions

[Gavin Shan]

There are three high memory regions, which are VIRT_HIGH_REDIST2,
VIRT_HIGH_PCIE_ECAM and VIRT_HIGH_PCIE_MMIO. Their base addresses
are floating on highest RAM address. However, they can be disabled
in several cases.

(1) One specific high memory region is disabled by developer by
    toggling vms->highmem_{redists, ecam, mmio}.

(2) VIRT_HIGH_PCIE_ECAM region is disabled on machine, which is
    'virt-2.12' or ealier than it.

(3) VIRT_HIGH_PCIE_ECAM region is disabled when firmware is loaded
    on 32-bits system.

(4) One specific high memory region is disabled when it breaks the
    PA space limit.

The current implementation of virt_set_memmap() isn't comprehensive
because the space for one specific high memory region is always
reserved from the PA space for case (1), (2) and (3). In the code,
'base' and 'vms->highest_gpa' are always increased for those three
cases. It's unnecessary since the assigned space of the disabled
high memory region won't be used afterwards.

This improves the address assignment for those three high memory
region by skipping the address assignment for one specific high
memory region if it has been disabled in case (1), (2) and (3).

Signed-off-by: Gavin Shan <gshan@redhat.com>
---
 hw/arm/virt.c | 42 +++++++++++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 582a8960fc..e38b6919c9 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1746,10 +1746,26 @@ static void virt_set_memmap(VirtMachineState *vms, int 
pa_bits)
     for (i = VIRT_LOWMEMMAP_LAST; i < ARRAY_SIZE(extended_memmap); i++) {
         hwaddr region_base = ROUND_UP(base, extended_memmap[i].size);
         hwaddr region_size = extended_memmap[i].size;
-        bool fits;
+        bool *region_enabled, fits;
 
-        vms->memmap[i].base = region_base;
-        vms->memmap[i].size = region_size;
+        switch (i) {
+        case VIRT_HIGH_GIC_REDIST2:
+            region_enabled = &vms->highmem_redists;
+            break;
+        case VIRT_HIGH_PCIE_ECAM:
+            region_enabled = &vms->highmem_ecam;
+            break;
+        case VIRT_HIGH_PCIE_MMIO:
+            region_enabled = &vms->highmem_mmio;
+            break;
+        default:
+            region_enabled = NULL;
+        }
+
+        /* Skip unknwon or disabled regions */
+        if (!region_enabled || !*region_enabled) {
+            continue;
+        }
 
         /*
          * Check each device to see if they fit in the PA space,
@@ -1759,22 +1775,14 @@ static void virt_set_memmap(VirtMachineState *vms, int 
pa_bits)
          */
         fits = (region_base + region_size) <= BIT_ULL(pa_bits);
         if (fits) {
-            vms->highest_gpa = region_base + region_size - 1;
-        }
+            vms->memmap[i].base = region_base;
+            vms->memmap[i].size = region_size;
 
-        switch (i) {
-        case VIRT_HIGH_GIC_REDIST2:
-            vms->highmem_redists &= fits;
-            break;
-        case VIRT_HIGH_PCIE_ECAM:
-            vms->highmem_ecam &= fits;
-            break;
-        case VIRT_HIGH_PCIE_MMIO:
-            vms->highmem_mmio &= fits;
-            break;
+            base = region_base + region_size;
+            vms->highest_gpa = region_base + region_size - 1;
+        } else {
+            *region_enabled = false;
         }
-
-        base = region_base + region_size;
     }
 
     if (device_memory_size > 0) {
-- 
2.23.0