[PATCH v5 5/6] hw/arm/virt: Improve high memory region address assignment

[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).
'vms->high_compact' is false for now, meaning that we don't have
any behavior changes until it becomes configurable through property
'compact-highmem' in next patch.

Signed-off-by: Gavin Shan <gshan@redhat.com>
Tested-by: Zhenyu Zhang <zhenyzha@redhat.com>
---
 hw/arm/virt.c         | 23 +++++++++++++++--------
 include/hw/arm/virt.h |  1 +
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index ee98a8a3b6..c05cfb5314 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1717,22 +1717,29 @@ static void virt_set_high_memmap(VirtMachineState *vms,
         region_base = ROUND_UP(base, extended_memmap[i].size);
         region_size = extended_memmap[i].size;
 
-        vms->memmap[i].base = region_base;
-        vms->memmap[i].size = region_size;
-
         /*
          * Check each device to see if they fit in the PA space,
-         * moving highest_gpa as we go.
+         * moving highest_gpa as we go. For compatibility, move
+         * highest_gpa for disabled fitting devices as well, if
+         * the compact layout has been disabled.
          *
          * For each device that doesn't fit, disable it.
          */
         fits = (region_base + region_size) <= BIT_ULL(pa_bits);
-        if (fits) {
+        if (*region_enabled && fits) {
+            vms->memmap[i].base = region_base;
+            vms->memmap[i].size = region_size;
             vms->highest_gpa = region_base + region_size - 1;
+            base = region_base + region_size;
+        } else {
+            *region_enabled = false;
+            if (!vms->highmem_compact) {
+                base = region_base + region_size;
+                if (fits) {
+                    vms->highest_gpa = region_base + region_size - 1;
+                }
+            }
         }
-
-        *region_enabled &= fits;
-        base = region_base + region_size;
     }
 }
 
diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
index 6ec479ca2b..709f623741 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -144,6 +144,7 @@ struct VirtMachineState {
     PFlashCFI01 *flash[2];
     bool secure;
     bool highmem;
+    bool highmem_compact;
     bool highmem_ecam;
     bool highmem_mmio;
     bool highmem_redists;
-- 
2.23.0