[Qemu-devel] [PATCH v6 16/16] VFIO: PLATFORM: add forwarded irq support

[Eric Auger]

Tests whether the forwarded IRQ modality is available.
In the positive device IRQs are forwarded. This control is
achieved with KVM-VFIO device. with such a modality injection
still is handled through irqfds. However end of interrupt is
not trapped anymore. As soon as the guest completes its virtual
IRQ, the corresponding physical IRQ is completed and the same
physical IRQ can hit again.

A new x-forward property enables to force forwarding off although
enabled by the kernel.

Signed-off-by: Eric Auger <address@hidden>
---
 hw/vfio/platform.c              | 52 +++++++++++++++++++++++++++++++++++++++++
 include/hw/vfio/vfio-platform.h |  2 ++
 trace-events                    |  1 +
 3 files changed, 55 insertions(+)

diff --git a/hw/vfio/platform.c b/hw/vfio/platform.c
index a59a842..2d07d2f 100644
--- a/hw/vfio/platform.c
+++ b/hw/vfio/platform.c
@@ -324,6 +324,52 @@ static void vfio_fake_intp_injection(void *opaque)
 }
 
 /*
+ * Functions used with forwarding capability
+ */
+
+#ifdef CONFIG_KVM
+
+static bool has_kvm_vfio_forward_capability(void)
+{
+    struct kvm_device_attr attr = {
+         .group = KVM_DEV_VFIO_DEVICE,
+         .attr = KVM_DEV_VFIO_DEVICE_FORWARD_IRQ};
+
+    if (ioctl(vfio_kvm_device_fd, KVM_HAS_DEVICE_ATTR, &attr) == 0) {
+        return true;
+    } else {
+        return false;
+    }
+}
+
+static int vfio_set_forwarding(VFIOINTp *intp)
+{
+    int ret;
+    struct kvm_device_attr attr = {
+         .group = KVM_DEV_VFIO_DEVICE,
+         .attr = KVM_DEV_VFIO_DEVICE_FORWARD_IRQ};
+
+    intp->fwd_irq = g_malloc0(sizeof(*intp->fwd_irq));
+    intp->fwd_irq->fd = intp->vdev->vbasedev.fd;
+    intp->fwd_irq->index = intp->pin;
+    intp->fwd_irq->gsi = intp->virtualID;
+
+    attr.addr = (uint64_t)(unsigned long)intp->fwd_irq;
+
+    if (ioctl(vfio_kvm_device_fd, KVM_SET_DEVICE_ATTR, &attr)) {
+            error_report("Failed to forward IRQ %d through KVM VFIO device",
+                         intp->pin);
+            g_free(intp->fwd_irq);
+            return -errno;
+    }
+    trace_vfio_start_fwd_injection(intp->pin);
+
+    return ret;
+}
+
+#endif
+
+/*
  * Functions used for irqfd
  */
 
@@ -375,6 +421,11 @@ static int vfio_start_irqfd_injection(VFIOINTp *intp)
         .flags = KVM_IRQFD_FLAG_RESAMPLE,
     };
 
+    if (has_kvm_vfio_forward_capability() &&
+                 intp->vdev->forward_allowed) {
+        vfio_set_forwarding(intp);
+    }
+
     if (kvm_vm_ioctl(kvm_state, KVM_IRQFD, &irqfd)) {
         error_report("vfio: Error: Failed to assign the irqfd: %m");
         goto fail_irqfd;
@@ -790,6 +841,7 @@ static Property vfio_platform_dev_properties[] = {
     DEFINE_PROP_UINT32("mmap-timeout-ms", VFIOPlatformDevice,
                        mmap_timeout, 1100),
     DEFINE_PROP_BOOL("x-irqfd", VFIOPlatformDevice, irqfd_allowed, true),
+    DEFINE_PROP_BOOL("x-forward", VFIOPlatformDevice, forward_allowed, true),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/include/hw/vfio/vfio-platform.h b/include/hw/vfio/vfio-platform.h
index e896c86..6c46295 100644
--- a/include/hw/vfio/vfio-platform.h
+++ b/include/hw/vfio/vfio-platform.h
@@ -48,6 +48,7 @@ typedef struct VFIOINTp {
     QEMUTimer *fake_eoi_timer; /* timer to handle fake IRQ completion */
     uint32_t fake_intp_period; /* delay between fake IRQ injections */
     uint32_t fake_intp_duration; /* duration of the IRQ */
+    struct kvm_arch_forwarded_irq *fwd_irq;
 } VFIOINTp;
 
 typedef int (*start_irq_fn_t)(VFIOINTp *intp);
@@ -72,6 +73,7 @@ typedef struct VFIOPlatformDevice {
     uint32_t len_x_fake_period;
     uint32_t len_x_fake_duration;
     bool irqfd_allowed; /* debug option to force irqfd on/off */
+    bool forward_allowed; /* debug option to force forwarding on/off */
 } VFIOPlatformDevice;
 
 
diff --git a/trace-events b/trace-events
index 1b81b66..29e03d2 100644
--- a/trace-events
+++ b/trace-events
@@ -1378,6 +1378,7 @@ vfio_get_device(const char * name, unsigned int flags, 
unsigned int num_regions,
 vfio_put_base_device(int fd) "close vdev->fd=%d"
 
 # hw/vfio/platform.c
+vfio_start_fwd_injection(int pin) "forwarding set for IRQ pin %d"
 vfio_platform_eoi(int pin, int fd) "EOI IRQ pin %d (fd=%d)"
 vfio_platform_mmap_set_enabled(bool enabled) "fast path = %d"
 vfio_platform_intp_mmap_enable(int pin) "IRQ #%d still active, stay in slow 
path"
-- 
1.8.3.2