5 files changed, 61 insertions, 17 deletions

diff --git a/hw/cxl/cxl-host.c b/hw/cxl/cxl-host.c
index 3c1ec8732a..6e923ceeaf 100644
--- a/hw/cxl/cxl-host.c
+++ b/hw/cxl/cxl-host.c
@@ -146,21 +146,28 @@ static PCIDevice *cxl_cfmws_find_device(CXLFixedWindow *fw, hwaddr addr)
         return NULL;
     }
 
-    hb_cstate = cxl_get_hb_cstate(hb);
-    if (!hb_cstate) {
-        return NULL;
-    }
+    if (cxl_get_hb_passthrough(hb)) {
+        rp = pcie_find_port_first(hb->bus);
+        if (!rp) {
+            return NULL;
+        }
+    } else {
+        hb_cstate = cxl_get_hb_cstate(hb);
+        if (!hb_cstate) {
+            return NULL;
+        }
 
-    cache_mem = hb_cstate->crb.cache_mem_registers;
+        cache_mem = hb_cstate->crb.cache_mem_registers;
 
-    target_found = cxl_hdm_find_target(cache_mem, addr, &target);
-    if (!target_found) {
-        return NULL;
-    }
+        target_found = cxl_hdm_find_target(cache_mem, addr, &target);
+        if (!target_found) {
+            return NULL;
+        }
 
-    rp = pcie_find_port_by_pn(hb->bus, target);
-    if (!rp) {
-        return NULL;
+        rp = pcie_find_port_by_pn(hb->bus, target);
+        if (!rp) {
+            return NULL;
+        }
     }
 
     d = pci_bridge_get_sec_bus(PCI_BRIDGE(rp))->devices[0];
diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
index e752a21292..ead33f0c05 100644
--- a/hw/pci-bridge/pci_expander_bridge.c
+++ b/hw/pci-bridge/pci_expander_bridge.c
@@ -15,6 +15,7 @@
 #include "hw/pci/pci.h"
 #include "hw/pci/pci_bus.h"
 #include "hw/pci/pci_host.h"
+#include "hw/pci/pcie_port.h"
 #include "hw/qdev-properties.h"
 #include "hw/pci/pci_bridge.h"
 #include "hw/pci-bridge/pci_expander_bridge.h"
@@ -79,6 +80,13 @@ CXLComponentState *cxl_get_hb_cstate(PCIHostState *hb)
     return &host->cxl_cstate;
 }
 
+bool cxl_get_hb_passthrough(PCIHostState *hb)
+{
+    CXLHost *host = PXB_CXL_HOST(hb);
+
+    return host->passthrough;
+}
+
 static int pxb_bus_num(PCIBus *bus)
 {
     PXBDev *pxb = convert_to_pxb(bus->parent_dev);
@@ -289,15 +297,32 @@ static int pxb_map_irq_fn(PCIDevice *pci_dev, int pin)
     return pin - PCI_SLOT(pxb->devfn);
 }
 
-static void pxb_dev_reset(DeviceState *dev)
+static void pxb_cxl_dev_reset(DeviceState *dev)
 {
     CXLHost *cxl = PXB_CXL_DEV(dev)->cxl.cxl_host_bridge;
     CXLComponentState *cxl_cstate = &cxl->cxl_cstate;
+    PCIHostState *hb = PCI_HOST_BRIDGE(cxl);
     uint32_t *reg_state = cxl_cstate->crb.cache_mem_registers;
     uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
+    int dsp_count = 0;
 
     cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
-    ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
+    /*
+     * The CXL specification allows for host bridges with no HDM decoders
+     * if they only have a single root port.
+     */
+    if (!PXB_DEV(dev)->hdm_for_passthrough) {
+        dsp_count = pcie_count_ds_ports(hb->bus);
+    }
+    /* Initial reset will have 0 dsp so wait until > 0 */
+    if (dsp_count == 1) {
+        cxl->passthrough = true;
+        /* Set Capability ID in header to NONE */
+        ARRAY_FIELD_DP32(reg_state, CXL_HDM_CAPABILITY_HEADER, ID, 0);
+    } else {
+        ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT,
+                         8);
+    }
 }
 
 static gint pxb_compare(gconstpointer a, gconstpointer b)
@@ -481,9 +506,18 @@ static void pxb_cxl_dev_realize(PCIDevice *dev, Error **errp)
     }
 
     pxb_dev_realize_common(dev, CXL, errp);
-    pxb_dev_reset(DEVICE(dev));
+    pxb_cxl_dev_reset(DEVICE(dev));
 }
 
+static Property pxb_cxl_dev_properties[] = {
+    /* Note: 0 is not a legal PXB bus number. */
+    DEFINE_PROP_UINT8("bus_nr", PXBDev, bus_nr, 0),
+    DEFINE_PROP_UINT16("numa_node", PXBDev, numa_node, NUMA_NODE_UNASSIGNED),
+    DEFINE_PROP_BOOL("bypass_iommu", PXBDev, bypass_iommu, false),
+    DEFINE_PROP_BOOL("hdm_for_passthrough", PXBDev, hdm_for_passthrough, false),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
 static void pxb_cxl_dev_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc   = DEVICE_CLASS(klass);
@@ -497,12 +531,12 @@ static void pxb_cxl_dev_class_init(ObjectClass *klass, void *data)
      */
 
     dc->desc = "CXL Host Bridge";
-    device_class_set_props(dc, pxb_dev_properties);
+    device_class_set_props(dc, pxb_cxl_dev_properties);
     set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
 
     /* Host bridges aren't hotpluggable. FIXME: spec reference */
     dc->hotpluggable = false;
-    dc->reset = pxb_dev_reset;
+    dc->reset = pxb_cxl_dev_reset;
 }
 
 static const TypeInfo pxb_cxl_dev_info = {
diff --git a/include/hw/cxl/cxl.h b/include/hw/cxl/cxl.h
index b161be59b7..b2cffbb364 100644
--- a/include/hw/cxl/cxl.h
+++ b/include/hw/cxl/cxl.h
@@ -49,6 +49,7 @@ struct CXLHost {
     PCIHostState parent_obj;
 
     CXLComponentState cxl_cstate;
+    bool passthrough;
 };
 
 #define TYPE_PXB_CXL_HOST "pxb-cxl-host"
diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
index ec4203b83f..42c7e581a7 100644
--- a/include/hw/cxl/cxl_component.h
+++ b/include/hw/cxl/cxl_component.h
@@ -247,6 +247,7 @@ static inline hwaddr cxl_decode_ig(int ig)
 }
 
 CXLComponentState *cxl_get_hb_cstate(PCIHostState *hb);
+bool cxl_get_hb_passthrough(PCIHostState *hb);
 
 void cxl_doe_cdat_init(CXLComponentState *cxl_cstate, Error **errp);
 void cxl_doe_cdat_release(CXLComponentState *cxl_cstate);
diff --git a/include/hw/pci/pci_bridge.h b/include/hw/pci/pci_bridge.h
index 63a7521567..81a058bb2c 100644
--- a/include/hw/pci/pci_bridge.h
+++ b/include/hw/pci/pci_bridge.h
@@ -92,6 +92,7 @@ struct PXBDev {
     uint8_t bus_nr;
     uint16_t numa_node;
     bool bypass_iommu;
+    bool hdm_for_passthrough;
     struct cxl_dev {
         CXLHost *cxl_host_bridge; /* Pointer to a CXLHost */
     } cxl;