qemu: ioeventfd for virtio-ccw.

index 5af9357..fc3d7ed 100644
@@ -448,12 +448,15 @@ enum {
 	kvm_ioeventfd_flag_nr_datamatch,
 	kvm_ioeventfd_flag_nr_pio,
 	kvm_ioeventfd_flag_nr_deassign,
+	kvm_ioeventfd_flag_nr_virtio_ccw_notify,
 	kvm_ioeventfd_flag_nr_max,
 };
 
 #define KVM_IOEVENTFD_FLAG_DATAMATCH (1 << kvm_ioeventfd_flag_nr_datamatch)
 #define KVM_IOEVENTFD_FLAG_PIO       (1 << kvm_ioeventfd_flag_nr_pio)
 #define KVM_IOEVENTFD_FLAG_DEASSIGN  (1 << kvm_ioeventfd_flag_nr_deassign)
+#define KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY \
+	(1 << kvm_ioeventfd_flag_nr_virtio_ccw_notify)
 
 #define KVM_IOEVENTFD_VALID_FLAG_MASK  ((1 << kvm_ioeventfd_flag_nr_max) - 1)
 

index 85f6f22..82e6746 100644
@@ -68,7 +68,7 @@ int css_create_css_image(uint8_t cssid, bool default_image)
     return 0;
 }
 
-static uint16_t css_build_subchannel_id(SubchDev *sch)
+uint16_t css_build_subchannel_id(SubchDev *sch)
 {
     if (channel_subsys->max_cssid > 0) {
         return (sch->cssid << 8) | (1 << 3) | (sch->ssid << 1) | 1;

index 85ed05d..b536ab5 100644
@@ -90,6 +90,7 @@ bool css_devno_used(uint8_t cssid, uint8_t ssid, uint16_t devno);
 void css_subch_assign(uint8_t cssid, uint8_t ssid, uint16_t schid,
                       uint16_t devno, SubchDev *sch);
 void css_sch_build_virtual_schib(SubchDev *sch, uint8_t chpid, uint8_t type);
+uint16_t css_build_subchannel_id(SubchDev *sch);
 void css_reset(void);
 void css_reset_sch(SubchDev *sch);
 void css_queue_crw(uint8_t rsc, uint8_t erc, int chain, uint16_t rsid);

217 lines not on this page · raw message

index 48474b3..db83e0f 100644
@@ -66,6 +66,11 @@ typedef struct VirtIOCCWDeviceClass {
 /* Change here if we want to support more feature bits. */
 #define VIRTIO_CCW_FEATURE_SIZE 1
 
+/* Performance improves when virtqueue kick processing is decoupled from the
+ * vcpu thread using ioeventfd for some devices. */
+#define VIRTIO_CCW_FLAG_USE_IOEVENTFD_BIT 1
+#define VIRTIO_CCW_FLAG_USE_IOEVENTFD   (1 << VIRTIO_CCW_FLAG_USE_IOEVENTFD_BIT)
+
 struct VirtioCcwDevice {
     DeviceState parent_obj;
     SubchDev *sch;

@@ -78,6 +83,8 @@ struct VirtioCcwDevice {
     virtio_net_conf net;
     VirtIOSCSIConf scsi;
     VirtioBusState bus;
+    bool ioeventfd_started;
+    uint32_t flags;
     /* Guest provided values: */
     hwaddr indicators;
     hwaddr indicators2;

index e450db7..3e891d4 100644
@@ -1068,6 +1068,7 @@ void kvm_s390_io_interrupt(S390CPU *cpu, uint16_t subchannel_id,
                            uint32_t io_int_word);
 void kvm_s390_crw_mchk(S390CPU *cpu);
 void kvm_s390_enable_css_support(S390CPU *cpu);
+int kvm_s390_assign_subch_ioeventfd(int fd, uint32_t sch, int vq, bool assign);
 #else
 static inline void kvm_s390_io_interrupt(S390CPU *cpu,
                                         uint16_t subchannel_id,

@@ -1082,6 +1083,11 @@ static inline void kvm_s390_crw_mchk(S390CPU *cpu)
 static inline void kvm_s390_enable_css_support(S390CPU *cpu)
 {
 }
+static inline int kvm_s390_assign_subch_ioeventfd(int fd, uint32_t sch, int vq,
+                                                  bool assign)
+{
+    return -ENOSYS;
+}
 #endif
 
 static inline void s390_io_interrupt(S390CPU *cpu,

@@ -1108,4 +1114,14 @@ static inline void s390_crw_mchk(S390CPU *cpu)
     }
 }
 
+static inline int s390_assign_subch_ioeventfd(int fd, uint32_t sch_id, int vq,
+                                              bool assign)
+{
+    if (kvm_enabled()) {
+        return kvm_s390_assign_subch_ioeventfd(fd, sch_id, vq, assign);
+    } else {
+        return -ENOSYS;
+    }
+}
+
 #endif

index 3929771..4237374 100644
@@ -847,3 +847,22 @@ void kvm_s390_enable_css_support(S390CPU *cpu)
     r = kvm_vcpu_ioctl(CPU(cpu), KVM_ENABLE_CAP, &cap);
     assert(r == 0);
 }
+
+int kvm_s390_assign_subch_ioeventfd(int fd, uint32_t sch, int vq, bool assign)
+{
+    struct kvm_ioeventfd kick = {
+        .flags = KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY |
+        KVM_IOEVENTFD_FLAG_DATAMATCH,
+        .fd = fd,
+        .datamatch = vq,
+        .addr = sch,
+        .len = 8,
+    };
+    if (!kvm_check_extension(kvm_state, KVM_CAP_IOEVENTFD)) {
+        return -ENOSYS;
+    }
+    if (!assign) {
+        kick.flags |= KVM_IOEVENTFD_FLAG_DEASSIGN;
+    }
+    return kvm_vm_ioctl(kvm_state, KVM_IOEVENTFD, &kick);
+}