[Qemu-devel] [PATCH v2 4/4] vfio/quirks: Enable ioeventfd quirks to be handled by vfio directly

[Alex Williamson <alex.williamson@redhat.com>]

With vfio ioeventfd support, we can program vfio-pci to perform a
specified BAR write when an eventfd is triggered.  This allows the
KVM ioeventfd to be wired directly to vfio-pci, entirely avoiding
userspace handling for these events.  On the same micro-benchmark
where the ioeventfd got us to almost 90% of performance versus
disabling the GeForce quirks, this gets us to within 95%.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 hw/vfio/pci-quirks.c |   50 +++++++++++++++++++++++++++++++++++++++++++-------
 hw/vfio/pci.c        |    2 ++
 hw/vfio/pci.h        |    2 ++
 hw/vfio/trace-events |    2 +-
 4 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c
index 4cedc733bc0a..94be27dd0a3b 100644
--- a/hw/vfio/pci-quirks.c
+++ b/hw/vfio/pci-quirks.c
@@ -16,6 +16,7 @@
 #include "qemu/range.h"
 #include "qapi/error.h"
 #include "qapi/visitor.h"
+#include <sys/ioctl.h>
 #include "hw/nvram/fw_cfg.h"
 #include "pci.h"
 #include "trace.h"
@@ -287,13 +288,31 @@ static VFIOQuirk *vfio_quirk_alloc(int nr_mem)
     return quirk;
 }
 
-static void vfio_ioeventfd_exit(VFIOIOEventFD *ioeventfd)
+static void vfio_ioeventfd_exit(VFIOPCIDevice *vdev, VFIOIOEventFD *ioeventfd)
 {
     QLIST_REMOVE(ioeventfd, next);
+
     memory_region_del_eventfd(ioeventfd->mr, ioeventfd->addr, ioeventfd->size,
                               ioeventfd->match_data, ioeventfd->data,
                               &ioeventfd->e);
-    qemu_set_fd_handler(event_notifier_get_fd(&ioeventfd->e), NULL, NULL, NULL);
+
+    if (ioeventfd->vfio) {
+        struct vfio_device_ioeventfd vfio_ioeventfd;
+
+        vfio_ioeventfd.argsz = sizeof(vfio_ioeventfd);
+        vfio_ioeventfd.flags = ioeventfd->size;
+        vfio_ioeventfd.data = ioeventfd->data;
+        vfio_ioeventfd.offset = ioeventfd->region->fd_offset +
+                                ioeventfd->region_addr;
+        vfio_ioeventfd.fd = -1;
+
+        ioctl(vdev->vbasedev.fd, VFIO_DEVICE_IOEVENTFD, &vfio_ioeventfd);
+
+    } else {
+        qemu_set_fd_handler(event_notifier_get_fd(&ioeventfd->e),
+                            NULL, NULL, NULL);
+    }
+
     event_notifier_cleanup(&ioeventfd->e);
     trace_vfio_ioeventfd_exit(memory_region_name(ioeventfd->mr),
                               (uint64_t)ioeventfd->addr, ioeventfd->size,
@@ -307,7 +326,7 @@ static void vfio_drop_dynamic_eventfds(VFIOPCIDevice *vdev, VFIOQuirk *quirk)
 
     QLIST_FOREACH_SAFE(ioeventfd, &quirk->ioeventfds, next, tmp) {
         if (ioeventfd->dynamic) {
-            vfio_ioeventfd_exit(ioeventfd);
+            vfio_ioeventfd_exit(vdev, ioeventfd);
         }
     }
 }
@@ -361,13 +380,30 @@ static VFIOIOEventFD *vfio_ioeventfd_init(VFIOPCIDevice *vdev,
     ioeventfd->region = region;
     ioeventfd->region_addr = region_addr;
 
-    qemu_set_fd_handler(event_notifier_get_fd(&ioeventfd->e),
-                        vfio_ioeventfd_handler, NULL, ioeventfd);
+    if (!vdev->no_vfio_ioeventfd) {
+        struct vfio_device_ioeventfd vfio_ioeventfd;
+
+        vfio_ioeventfd.argsz = sizeof(vfio_ioeventfd);
+        vfio_ioeventfd.flags = ioeventfd->size;
+        vfio_ioeventfd.data = ioeventfd->data;
+        vfio_ioeventfd.offset = ioeventfd->region->fd_offset +
+                                ioeventfd->region_addr;
+        vfio_ioeventfd.fd = event_notifier_get_fd(&ioeventfd->e);
+
+        ioeventfd->vfio = !ioctl(vdev->vbasedev.fd,
+                                 VFIO_DEVICE_IOEVENTFD, &vfio_ioeventfd);
+    }
+
+    if (!ioeventfd->vfio) {
+        qemu_set_fd_handler(event_notifier_get_fd(&ioeventfd->e),
+                            vfio_ioeventfd_handler, NULL, ioeventfd);
+    }
+
     memory_region_add_eventfd(ioeventfd->mr, ioeventfd->addr,
                               ioeventfd->size, ioeventfd->match_data,
                               ioeventfd->data, &ioeventfd->e);
     trace_vfio_ioeventfd_init(memory_region_name(mr), (uint64_t)addr,
-                              size, data);
+                              size, data, ioeventfd->vfio);
 
     return ioeventfd;
 }
@@ -1835,7 +1871,7 @@ void vfio_bar_quirk_exit(VFIOPCIDevice *vdev, int nr)
 
     QLIST_FOREACH(quirk, &bar->quirks, next) {
         while (!QLIST_EMPTY(&quirk->ioeventfds)) {
-            vfio_ioeventfd_exit(QLIST_FIRST(&quirk->ioeventfds));
+            vfio_ioeventfd_exit(vdev, QLIST_FIRST(&quirk->ioeventfds));
         }
 
         for (i = 0; i < quirk->nr_mem; i++) {
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index ba1239551115..84e27c7bb2d1 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3177,6 +3177,8 @@ static Property vfio_pci_dev_properties[] = {
                      no_geforce_quirks, false),
     DEFINE_PROP_BOOL("x-no-kvm-ioeventfd", VFIOPCIDevice, no_kvm_ioeventfd,
                      false),
+    DEFINE_PROP_BOOL("x-no-vfio-ioeventfd", VFIOPCIDevice, no_vfio_ioeventfd,
+                     false),
     DEFINE_PROP_UINT32("x-pci-vendor-id", VFIOPCIDevice, vendor_id, PCI_ANY_ID),
     DEFINE_PROP_UINT32("x-pci-device-id", VFIOPCIDevice, device_id, PCI_ANY_ID),
     DEFINE_PROP_UINT32("x-pci-sub-vendor-id", VFIOPCIDevice,
diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
index dbb3aca9b3d2..dbb3932b50ef 100644
--- a/hw/vfio/pci.h
+++ b/hw/vfio/pci.h
@@ -35,6 +35,7 @@ typedef struct VFIOIOEventFD {
     hwaddr region_addr;
     bool match_data;
     bool dynamic;
+    bool vfio;
 } VFIOIOEventFD;
 
 typedef struct VFIOQuirk {
@@ -164,6 +165,7 @@ typedef struct VFIOPCIDevice {
     bool no_kvm_msix;
     bool no_geforce_quirks;
     bool no_kvm_ioeventfd;
+    bool no_vfio_ioeventfd;
     VFIODisplay *dpy;
 } VFIOPCIDevice;
 
diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
index f8f97d1ff90c..d2a74952e389 100644
--- a/hw/vfio/trace-events
+++ b/hw/vfio/trace-events
@@ -79,7 +79,7 @@ vfio_quirk_ati_bonaire_reset_done(const char *name) "%s"
 vfio_quirk_ati_bonaire_reset(const char *name) "%s"
 vfio_ioeventfd_exit(const char *name, uint64_t addr, unsigned size, uint64_t data) "%s+0x%"PRIx64"[%d]:0x%"PRIx64
 vfio_ioeventfd_handler(const char *name, uint64_t addr, unsigned size, uint64_t data) "%s+0x%"PRIx64"[%d] -> 0x%"PRIx64
-vfio_ioeventfd_init(const char *name, uint64_t addr, unsigned size, uint64_t data) "%s+0x%"PRIx64"[%d]:0x%"PRIx64
+vfio_ioeventfd_init(const char *name, uint64_t addr, unsigned size, uint64_t data, bool vfio) "%s+0x%"PRIx64"[%d]:0x%"PRIx64" vfio:%d"
 vfio_pci_igd_bar4_write(const char *name, uint32_t index, uint32_t data, uint32_t base) "%s [0x%03x] 0x%08x -> 0x%08x"
 vfio_pci_igd_bdsm_enabled(const char *name, int size) "%s %dMB"
 vfio_pci_igd_opregion_enabled(const char *name) "%s"