[PATCH v3 2/3] pci-assign: Use PCI-2.3-based shared legacy interrupts

[Jan Kiszka <jan.kiszka@siemens.com>]

Enable the new KVM feature that allows legacy interrupt sharing for
PCI-2.3-compliant devices. This requires to synchronize any guest
change of the INTx mask bit to the kernel.

The feature is controlled by the property 'share_intx' and is off by
default for now.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

Changes in v3:
 - fixed nit :)

 hw/device-assignment.c |   24 ++++++++++++++++++++++++
 hw/device-assignment.h |   10 ++++++----
 qemu-kvm.c             |    9 +++++++++
 qemu-kvm.h             |    2 ++
 4 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/hw/device-assignment.c b/hw/device-assignment.c
index a5f1abb..e2a8479 100644
--- a/hw/device-assignment.c
+++ b/hw/device-assignment.c
@@ -782,6 +782,13 @@ static int assign_device(AssignedDevice *dev)
                 "cause host memory corruption if the device issues DMA write "
                 "requests!\n");
     }
+    if (dev->features & ASSIGNED_DEVICE_SHARE_INTX_MASK) {
+        assigned_dev_data.flags |= KVM_DEV_ASSIGN_PCI_2_3;
+
+        /* hide host-side INTx masking from the guest */
+        dev->emulate_config_read[PCI_COMMAND + 1] |=
+            PCI_COMMAND_INTX_DISABLE >> 8;
+    }
 
     r = kvm_assign_pci_device(kvm_state, &assigned_dev_data);
     if (r < 0) {
@@ -1121,10 +1128,25 @@ static void assigned_dev_pci_write_config(PCIDevice *pci_dev, uint32_t address,
                                           uint32_t val, int len)
 {
     AssignedDevice *assigned_dev = DO_UPCAST(AssignedDevice, dev, pci_dev);
+    uint16_t old_cmd = pci_get_word(pci_dev->config + PCI_COMMAND);
     uint32_t emulate_mask, full_emulation_mask;
+    int ret;
 
     pci_default_write_config(pci_dev, address, val, len);
 
+    if (range_covers_byte(address, len, PCI_COMMAND + 1)) {
+        bool intx_masked = (pci_get_word(pci_dev->config + PCI_COMMAND) &
+                            PCI_COMMAND_INTX_DISABLE);
+
+        if (intx_masked != !!(old_cmd & PCI_COMMAND_INTX_DISABLE)) {
+            ret = kvm_device_intx_set_mask(kvm_state,
+                                           calc_assigned_dev_id(assigned_dev),
+                                           intx_masked);
+            if (ret) {
+                perror("assigned_dev_pci_write_config: set intx mask");
+            }
+        }
+    }
     if (assigned_dev->cap.available & ASSIGNED_DEVICE_CAP_MSI) {
         if (range_covers_byte(address, len,
                               pci_dev->msi_cap + PCI_MSI_FLAGS)) {
@@ -1748,6 +1770,8 @@ static Property da_properties[] =
                    ASSIGNED_DEVICE_USE_IOMMU_BIT, true),
     DEFINE_PROP_BIT("prefer_msi", AssignedDevice, features,
                    ASSIGNED_DEVICE_PREFER_MSI_BIT, true),
+    DEFINE_PROP_BIT("share_intx", AssignedDevice, features,
+                    ASSIGNED_DEVICE_SHARE_INTX_BIT, false),
     DEFINE_PROP_INT32("bootindex", AssignedDevice, bootindex, -1),
     DEFINE_PROP_STRING("configfd", AssignedDevice, configfd_name),
     DEFINE_PROP_END_OF_LIST(),
diff --git a/hw/device-assignment.h b/hw/device-assignment.h
index b4bcfa6..5d271d5 100644
--- a/hw/device-assignment.h
+++ b/hw/device-assignment.h
@@ -74,11 +74,13 @@ typedef struct {
     PCIRegion *region;
 } AssignedDevRegion;
 
-#define ASSIGNED_DEVICE_USE_IOMMU_BIT	0
-#define ASSIGNED_DEVICE_PREFER_MSI_BIT	1
+#define ASSIGNED_DEVICE_USE_IOMMU_BIT   0
+#define ASSIGNED_DEVICE_PREFER_MSI_BIT  1
+#define ASSIGNED_DEVICE_SHARE_INTX_BIT  2
 
-#define ASSIGNED_DEVICE_USE_IOMMU_MASK	(1 << ASSIGNED_DEVICE_USE_IOMMU_BIT)
-#define ASSIGNED_DEVICE_PREFER_MSI_MASK	(1 << ASSIGNED_DEVICE_PREFER_MSI_BIT)
+#define ASSIGNED_DEVICE_USE_IOMMU_MASK  (1 << ASSIGNED_DEVICE_USE_IOMMU_BIT)
+#define ASSIGNED_DEVICE_PREFER_MSI_MASK (1 << ASSIGNED_DEVICE_PREFER_MSI_BIT)
+#define ASSIGNED_DEVICE_SHARE_INTX_MASK (1 << ASSIGNED_DEVICE_SHARE_INTX_BIT)
 
 typedef struct {
     uint32_t addr_lo;
diff --git a/qemu-kvm.c b/qemu-kvm.c
index 09a35f0..2047ebb 100644
--- a/qemu-kvm.c
+++ b/qemu-kvm.c
@@ -54,6 +54,15 @@ static int kvm_old_assign_irq(KVMState *s,
     return kvm_vm_ioctl(s, KVM_ASSIGN_IRQ, assigned_irq);
 }
 
+int kvm_device_intx_set_mask(KVMState *s, uint32_t dev_id, bool masked)
+{
+    struct kvm_assigned_pci_dev assigned_dev;
+
+    assigned_dev.assigned_dev_id = dev_id;
+    assigned_dev.flags = masked ? KVM_DEV_ASSIGN_MASK_INTX : 0;
+    return kvm_vm_ioctl(s, KVM_ASSIGN_SET_INTX_MASK, &assigned_dev);
+}
+
 #ifdef KVM_CAP_ASSIGN_DEV_IRQ
 int kvm_assign_irq(KVMState *s, struct kvm_assigned_irq *assigned_irq)
 {
diff --git a/qemu-kvm.h b/qemu-kvm.h
index 3c4f023..2b23daf 100644
--- a/qemu-kvm.h
+++ b/qemu-kvm.h
@@ -114,6 +114,8 @@ int kvm_assign_irq(KVMState *s, struct kvm_assigned_irq *assigned_irq);
  */
 int kvm_deassign_irq(KVMState *s, struct kvm_assigned_irq *assigned_irq);
 
+int kvm_device_intx_set_mask(KVMState *s, uint32_t dev_id, bool masked);
+
 /*!
  * \brief Notifies host kernel about a PCI device to be deassigned from a guest
  *
-- 
1.7.3.4