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 |   53 +++++++++++++++++++++++++++++++++++++++++++-------
 hw/vfio/pci.c        |    2 ++
 hw/vfio/pci.h        |    2 ++
 hw/vfio/trace-events |    2 +-
 4 files changed, 51 insertions(+), 8 deletions(-)

diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c
index f7886487744e..061259b86b71 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"
@@ -287,12 +288,33 @@ 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,
                               true, 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;
+
+        if (ioctl(vdev->vbasedev.fd, VFIO_DEVICE_IOEVENTFD, &vfio_ioeventfd)) {
+            error_report("Failed to remove vfio ioeventfd for %s+0x%"
+                         HWADDR_PRIx"[%d]:0x%"PRIx64" (%m)",
+                         memory_region_name(ioeventfd->mr), ioeventfd->addr,
+                         ioeventfd->size, ioeventfd->data);
+        }
+    } 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,
@@ -306,7 +328,7 @@ 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);
         }
     }
 }
@@ -359,12 +381,29 @@ 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,
                               true, ioeventfd->data, &ioeventfd->e);
     trace_vfio_ioeventfd_init(memory_region_name(mr), (uint64_t)addr,
-                              size, data);
+                              size, data, ioeventfd->vfio);
 
     return ioeventfd;
 }
@@ -1827,7 +1866,7 @@ 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 a4ac583fbd6e..52b065421a68 100644
--- a/hw/vfio/pci.h
+++ b/hw/vfio/pci.h
@@ -34,6 +34,7 @@ typedef struct VFIOIOEventFD {
     VFIORegion *region;
     hwaddr region_addr;
     bool dynamic; /* Added runtime, removed on device reset */
+    bool vfio;
 } VFIOIOEventFD;
 
 typedef struct VFIOQuirk {
@@ -163,6 +164,7 @@ 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"

On Thu, May 03, 2018 at 03:45:13PM -0600, Alex Williamson wrote:
> 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>

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu

Hi,

On 05/03/2018 11:45 PM, Alex Williamson wrote:
> 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>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric
> ---
>  hw/vfio/pci-quirks.c |   53 +++++++++++++++++++++++++++++++++++++++++++-------
>  hw/vfio/pci.c        |    2 ++
>  hw/vfio/pci.h        |    2 ++
>  hw/vfio/trace-events |    2 +-
>  4 files changed, 51 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c
> index f7886487744e..061259b86b71 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"
> @@ -287,12 +288,33 @@ 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,
>                                true, 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;
> +
> +        if (ioctl(vdev->vbasedev.fd, VFIO_DEVICE_IOEVENTFD, &vfio_ioeventfd)) {
> +            error_report("Failed to remove vfio ioeventfd for %s+0x%"
> +                         HWADDR_PRIx"[%d]:0x%"PRIx64" (%m)",
> +                         memory_region_name(ioeventfd->mr), ioeventfd->addr,
> +                         ioeventfd->size, ioeventfd->data);
> +        }
> +    } 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,
> @@ -306,7 +328,7 @@ 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);
>          }
>      }
>  }
> @@ -359,12 +381,29 @@ 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,
>                                true, ioeventfd->data, &ioeventfd->e);
>      trace_vfio_ioeventfd_init(memory_region_name(mr), (uint64_t)addr,
> -                              size, data);
> +                              size, data, ioeventfd->vfio);
>  
>      return ioeventfd;
>  }
> @@ -1827,7 +1866,7 @@ 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 a4ac583fbd6e..52b065421a68 100644
> --- a/hw/vfio/pci.h
> +++ b/hw/vfio/pci.h
> @@ -34,6 +34,7 @@ typedef struct VFIOIOEventFD {
>      VFIORegion *region;
>      hwaddr region_addr;
>      bool dynamic; /* Added runtime, removed on device reset */
> +    bool vfio;
>  } VFIOIOEventFD;
>  
>  typedef struct VFIOQuirk {
> @@ -163,6 +164,7 @@ 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"
>