[SeaBIOS] [RFC] map 64-bit PCI devices after all possible RAM

[Igor Mammedov]

I'm posting it to get an oppinion on one of possible approaches
on where to map a hotplug memory.

This patch assumes that a space for hotplug memory is located right
after RamSizeOver4G region and QEMU will provide romfile to specify
where it ends so that BIOS could know from what base to start
64-bit PCI devices mapping.

Signed-off-by: Igor Mammedov 
---
 src/fw/pciinit.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
index b29db99..62f8d4e 100644
--- a/src/fw/pciinit.c
+++ b/src/fw/pciinit.c
@@ -18,6 +18,8 @@
 #include "paravirt.h" // RamSize
 #include "string.h" // memset
 #include "util.h" // pci_setup
+#include "byteorder.h" // le64_to_cpu
+#include "romfile.h" // romfile_loadint

#define PCI_DEVICE_MEM_MIN     0x1000
 #define PCI_BRIDGE_IO_MIN      0x1000
@@ -764,6 +766,8 @@ static void pci_bios_map_devices(struct pci_bus *busses)
 {
     if (pci_bios_init_root_regions(busses)) {
         struct pci_region r64_mem, r64_pref;
+        u64 base64 = le64_to_cpu(romfile_loadint("etc/mem64-end",
+                                 0x100000000ULL + RamSizeOver4G));
         r64_mem.list.first = NULL;
         r64_pref.list.first = NULL;
         pci_region_migrate_64bit_entries(&busses[0].r[PCI_REGION_TYPE_MEM],
@@ -779,7 +783,7 @@ static void pci_bios_map_devices(struct pci_bus *busses)
         u64 align_mem = pci_region_align(&r64_mem);
         u64 align_pref = pci_region_align(&r64_pref);

-        r64_mem.base = ALIGN(0x100000000LL + RamSizeOver4G, align_mem);
+        r64_mem.base = ALIGN(base64, align_mem);
         r64_pref.base = ALIGN(r64_mem.base + sum_mem, align_pref);
         pcimem64_start = r64_mem.base;
         pcimem64_end = r64_pref.base + sum_pref;