[PATCH] WHPX: Add support for device backed memory regions

[Aidan Khoury <aidan@revers.engineering>]

Due to skipping the mapping of read only device memory, Windows
Hypervisor Platform would fail to emulate such memory accesses when booting
OVMF EDK2 firmware. This patch adds ROM device memory region support
for WHPX since the Windows Hypervisor Platform supports mapping read-only
device memory, which allows successful booting of OVMF EDK2 firmware.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/513
          https://gitlab.com/qemu-project/qemu/-/issues/934
Buglink: https://bugs.launchpad.net/bugs/1821595

Signed-off-by: Aidan Khoury <aidan@revers.engineering>
---
 target/i386/whpx/whpx-all.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/target/i386/whpx/whpx-all.c b/target/i386/whpx/whpx-all.c
index b22a3314b4..7a61df1135 100644
--- a/target/i386/whpx/whpx-all.c
+++ b/target/i386/whpx/whpx-all.c
@@ -2363,11 +2363,18 @@ static void whpx_process_section(MemoryRegionSection *section, int add)
     MemoryRegion *mr = section->mr;
     hwaddr start_pa = section->offset_within_address_space;
     ram_addr_t size = int128_get64(section->size);
+    bool is_romd = false;
     unsigned int delta;
     uint64_t host_va;
 
     if (!memory_region_is_ram(mr)) {
-        return;
+        if (memory_region_is_romd(mr)) {
+            is_romd = true;
+            warn_report("WHPX: ROMD region 0x%016" PRIx64 "->0x%016" PRIx64,
+                        start_pa, start_pa + size);
+        } else {
+            return;
+        }
     }
 
     delta = qemu_real_host_page_size() - (start_pa & ~qemu_real_host_page_mask());
@@ -2386,7 +2393,7 @@ static void whpx_process_section(MemoryRegionSection *section, int add)
             + section->offset_within_region + delta;
 
     whpx_update_mapping(start_pa, size, (void *)(uintptr_t)host_va, add,
-                        memory_region_is_rom(mr), mr->name);
+                        memory_region_is_rom(mr) || is_romd, mr->name);
 }
 
 static void whpx_region_add(MemoryListener *listener,
-- 
2.37.1