[Qemu-devel] [PATCH 2/2] pc: add 'etc/reserved-memory-end' fw_cfg interface for SeaBIOS

[Igor Mammedov]

'etc/reserved-memory-end' will allow QEMU to tell BIOS where PCI
BARs mapping could safely start in high memory.

Allowing BIOS to start mapping 64-bit PCI BARs at address where it
wouldn't conflict with other mappings QEMU might place before it.

That permits QEMU to reserve extra address space before
64-bit PCI hole for memory hotplug.

Signed-off-by: Igor Mammedov <address@hidden>
---
 hw/i386/pc.c         | 14 +++++++++++++-
 hw/pci-host/piix.c   |  3 ++-
 hw/pci-host/q35.c    |  3 ++-
 include/hw/i386/pc.h |  3 ++-
 4 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 6c82ada..b504047 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1095,11 +1095,23 @@ PcGuestInfo *pc_guest_info_init(ram_addr_t 
below_4g_mem_size,
 
 /* setup pci memory address space mapping into system address space */
 void pc_pci_as_mapping_init(Object *owner, MemoryRegion *system_memory,
-                            MemoryRegion *pci_address_space)
+                            MemoryRegion *pci_address_space,
+                            uint64_t reserved_memory_end)
 {
+    uint64_t *val;
+    FWCfgState *fw_cfg = fw_cfg_find();
+
     /* Set to lower priority than RAM */
     memory_region_add_subregion_overlap(system_memory, 0x0,
                                         pci_address_space, -1);
+    g_assert(fw_cfg);
+    /*
+     *  Align address at 1G, this makes sure it can be exactly covered
+     *  with a PAT entry even when using huge pages.
+     */
+    val = g_malloc(sizeof(*val));
+    *val = cpu_to_le64(ROUND_UP(reserved_memory_end, 0x1ULL << 30));
+    fw_cfg_add_file(fw_cfg, "etc/reserved-memory-end", val, sizeof(*val));
 }
 
 void pc_acpi_init(const char *default_dsdt)
diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
index 5d4e290..16205e7 100644
--- a/hw/pci-host/piix.c
+++ b/hw/pci-host/piix.c
@@ -351,7 +351,8 @@ PCIBus *i440fx_init(PCII440FXState **pi440fx_state,
 
     /* setup pci memory mapping */
     pc_pci_as_mapping_init(OBJECT(f), f->system_memory,
-                           f->pci_address_space);
+                           f->pci_address_space,
+                           0x100000000ULL + above_4g_mem_size);
 
     memory_region_init_alias(&f->smram_region, OBJECT(d), "smram-region",
                              f->pci_address_space, 0xa0000, 0x20000);
diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
index d1792de..1293353 100644
--- a/hw/pci-host/q35.c
+++ b/hw/pci-host/q35.c
@@ -353,7 +353,8 @@ static int mch_init(PCIDevice *d)
 
     /* setup pci memory mapping */
     pc_pci_as_mapping_init(OBJECT(mch), mch->system_memory,
-                           mch->pci_address_space);
+                           mch->pci_address_space,
+                           0x100000000ULL + mch->above_4g_mem_size);
 
     /* smram */
     cpu_smm_register(&mch_set_smm, mch);
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 8b3be3c..2663046 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -130,7 +130,8 @@ PcGuestInfo *pc_guest_info_init(ram_addr_t 
below_4g_mem_size,
 
 
 void pc_pci_as_mapping_init(Object *owner, MemoryRegion *system_memory,
-                            MemoryRegion *pci_address_space);
+                            MemoryRegion *pci_address_space,
+                            uint64_t reserved_memory_end);
 
 FWCfgState *pc_memory_init(MemoryRegion *system_memory,
                            const char *kernel_filename,
-- 
1.8.3.1