[Qemu-devel] [PATCH] hw/pci: reserve IO and mem for pci express downstream ports with no devices attached

[Marcel Apfelbaum <marcel.a@redhat.com>]

commit c6e298e1f12e0f4ca02b6da5e42919ae055f6830
    hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached

introduced support for hot-plugging devices behind pci-2-pci bridges.
Extend hotplug support also for pci express downstream ports.

Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
---
 src/fw/pciinit.c  | 23 +++++++++++++++++++++--
 src/hw/pci_regs.h |  2 ++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
index 0ad548f..edb3fe9 100644
--- a/src/fw/pciinit.c
+++ b/src/fw/pciinit.c
@@ -636,6 +636,25 @@ pci_region_create_entry(struct pci_bus *bus, struct pci_device *dev,
     return entry;
 }
 
+static int pci_bus_hotplug_support(struct pci_bus *bus)
+{
+    u8 shpc_cap = pci_find_capability(bus->bus_dev, PCI_CAP_ID_SHPC);
+    u8 pcie_cap = pci_find_capability(bus->bus_dev, PCI_CAP_ID_EXP);
+    int downstream_port = 0;
+    int slot_implemented = 0;
+
+    if (pcie_cap) {
+        u16 pcie_flags = pci_config_readw(bus->bus_dev->bdf,
+                                          pcie_cap + PCI_EXP_FLAGS);
+        u16 port_type = ((pcie_flags & PCI_EXP_FLAGS_TYPE) >>
+                        PCI_EXP_FLAGS_TYPE_SHIFT) & 0xf;
+        downstream_port = (port_type == PCI_EXP_TYPE_DOWNSTREAM) ||
+                          (port_type == PCI_EXP_TYPE_ROOT_PORT);
+        slot_implemented = !!(pcie_flags & PCI_EXP_FLAGS_SLOT);
+    }
+    return shpc_cap || (downstream_port && slot_implemented);
+}
+
 static int pci_bios_check_devices(struct pci_bus *busses)
 {
     dprintf(1, "PCI: check devices\n");
@@ -678,7 +697,7 @@ static int pci_bios_check_devices(struct pci_bus *busses)
             continue;
         struct pci_bus *parent = &busses[pci_bdf_to_bus(s->bus_dev->bdf)];
         int type;
-        u8 shpc_cap = pci_find_capability(s->bus_dev, PCI_CAP_ID_SHPC);
+        int hotplug_support = pci_bus_hotplug_support(s);
         for (type = 0; type < PCI_REGION_TYPE_COUNT; type++) {
             u64 align = (type == PCI_REGION_TYPE_IO) ?
                 PCI_BRIDGE_IO_MIN : PCI_BRIDGE_MEM_MIN;
@@ -687,7 +706,7 @@ static int pci_bios_check_devices(struct pci_bus *busses)
             if (pci_region_align(&s->r[type]) > align)
                  align = pci_region_align(&s->r[type]);
             u64 sum = pci_region_sum(&s->r[type]);
-            if (!sum && shpc_cap)
+            if (!sum && hotplug_support)
                 sum = align; /* reserve min size for hot-plug */
             u64 size = ALIGN(sum, align);
             int is64 = pci_bios_bridge_region_is64(&s->r[type],
diff --git a/src/hw/pci_regs.h b/src/hw/pci_regs.h
index e5effd4..6a71569 100644
--- a/src/hw/pci_regs.h
+++ b/src/hw/pci_regs.h
@@ -426,6 +426,8 @@
 #define PCI_EXP_DEVCTL2		40	/* Device Control 2 */
 #define  PCI_EXP_DEVCTL2_ARI	0x20	/* Alternative Routing-ID */
 
+#define PCI_EXP_FLAGS_TYPE_SHIFT 4
+
 /* Extended Capabilities (PCI-X 2.0 and Express) */
 #define PCI_EXT_CAP_ID(header)		(header & 0x0000ffff)
 #define PCI_EXT_CAP_VER(header)		((header >> 16) & 0xf)
-- 
1.8.3.1