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[Qemu-devel] [PATCH v2] pci: fix pci_requester_id()


From: Peter Xu
Subject: [Qemu-devel] [PATCH v2] pci: fix pci_requester_id()
Date: Mon, 16 May 2016 15:13:20 +0800

The original pci_requester_id() is not really getting requester ID, but
only BDF. It will not work if we enable IOMMU IR with SID verifications
when with PCI bridges.  Renaming it to pci_get_bdf().

Meanwhile, we provide the correct implementation to get requester
ID. VT-d spec 5.1.1 is a good reference to go, though it talks only
about interrupt delivery, the rule works exactly the same for
non-interrupt cases.

Currently, there are three use cases for pci_requester_id():

- PCIX status bits: here we need BDF only, not requester ID. Replacing
  with pci_get_bdf().
- PCIe Error injection and MSI delivery: for both these cases, we are
  looking for requester IDs. Kept untouched to leverage the new impl.

Signed-off-by: Peter Xu <address@hidden>
---
 hw/i386/kvm/pci-assign.c |  2 +-
 hw/pci/pci.c             | 29 +++++++++++++++++++++++++++++
 include/hw/pci/pci.h     |  7 +++++--
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/hw/i386/kvm/pci-assign.c b/hw/i386/kvm/pci-assign.c
index bf425a2..c40ab36 100644
--- a/hw/i386/kvm/pci-assign.c
+++ b/hw/i386/kvm/pci-assign.c
@@ -1481,7 +1481,7 @@ static int assigned_device_pci_cap_init(PCIDevice 
*pci_dev, Error **errp)
          * error bits, leave the rest. */
         status = pci_get_long(pci_dev->config + pos + PCI_X_STATUS);
         status &= ~(PCI_X_STATUS_BUS | PCI_X_STATUS_DEVFN);
-        status |= pci_requester_id(pci_dev);
+        status |= pci_get_bdf(pci_dev);
         status &= ~(PCI_X_STATUS_SPL_DISC | PCI_X_STATUS_UNX_SPL |
                     PCI_X_STATUS_SPL_ERR);
         pci_set_long(pci_dev->config + pos + PCI_X_STATUS, status);
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index bb605ef..7430715 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -2498,6 +2498,35 @@ PCIDevice *pci_get_function_0(PCIDevice *pci_dev)
     }
 }
 
+/* Parse bridges up to the root complex and get final Requester ID
+ * for this device.  For PCIe-all topology, this works exactly as
+ * pci_get_bdf() does. However, several tricks are required for
+ * legacy PCI topology and PCIe-to-PCI bridges, to be better aligned
+ * with spec. */
+uint16_t pci_requester_id(PCIDevice *dev)
+{
+    uint8_t bus_n;
+    uint16_t result = pci_get_bdf(dev);
+    while ((bus_n = pci_bus_num(dev->bus))) {
+        /* We are under PCI/PCIe bridges */
+        dev = dev->bus->parent_dev;
+        if (pci_is_express(dev)) {
+            if (pcie_cap_get_type(dev) == PCI_EXP_TYPE_PCI_BRIDGE) {
+                /* When we pass through PCIe-to-PCI/PCIX bridges, we
+                 * override the requester ID using secondary bus
+                 * number with zeroed devfn (pcie-to-pci bridge spec
+                 * chap 2.3). */
+                result = PCI_BUILD_BDF(bus_n, 0);
+            }
+        } else {
+            /* Legacy PCI bus, override requester ID with the
+             * bridge's BDF upstream. */
+            result = pci_get_bdf(dev);
+        }
+    }
+    return result;
+}
+
 static const TypeInfo pci_device_type_info = {
     .name = TYPE_PCI_DEVICE,
     .parent = TYPE_DEVICE,
diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index ef6ba51..351266c 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -15,6 +15,7 @@
 #define PCI_DEVFN(slot, func)   ((((slot) & 0x1f) << 3) | ((func) & 0x07))
 #define PCI_SLOT(devfn)         (((devfn) >> 3) & 0x1f)
 #define PCI_FUNC(devfn)         ((devfn) & 0x07)
+#define PCI_BUILD_BDF(bus, devfn)     ((bus << 8) | (devfn))
 #define PCI_SLOT_MAX            32
 #define PCI_FUNC_MAX            8
 
@@ -685,11 +686,13 @@ static inline uint32_t pci_config_size(const PCIDevice *d)
     return pci_is_express(d) ? PCIE_CONFIG_SPACE_SIZE : PCI_CONFIG_SPACE_SIZE;
 }
 
-static inline uint16_t pci_requester_id(PCIDevice *dev)
+static inline uint16_t pci_get_bdf(PCIDevice *dev)
 {
-    return (pci_bus_num(dev->bus) << 8) | dev->devfn;
+    return PCI_BUILD_BDF(pci_bus_num(dev->bus), dev->devfn);
 }
 
+uint16_t pci_requester_id(PCIDevice *dev);
+
 /* DMA access functions */
 static inline AddressSpace *pci_get_address_space(PCIDevice *dev)
 {
-- 
2.4.11




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