[1/2] vfio: ABI for setting mdev display flip eventfd
diff mbox series

Message ID 20190527084312.8872-2-tina.zhang@intel.com
State New
Headers show
Series
  • Deliver vGPU page flip event to userspace
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Commit Message

Tina Zhang May 27, 2019, 8:43 a.m. UTC
Add VFIO_DEVICE_SET_GFX_FLIP_EVENTFD ioctl command to set eventfd
based signaling mechanism to deliver vGPU framebuffer page flip
event to userspace.

Signed-off-by: Tina Zhang <tina.zhang@intel.com>
---
 include/uapi/linux/vfio.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Comments

Zhenyu Wang May 27, 2019, 9:07 a.m. UTC | #1
On 2019.05.27 16:43:11 +0800, Tina Zhang wrote:
> Add VFIO_DEVICE_SET_GFX_FLIP_EVENTFD ioctl command to set eventfd
> based signaling mechanism to deliver vGPU framebuffer page flip
> event to userspace.
>

Should we add probe to see if driver can support gfx flip event?

> Signed-off-by: Tina Zhang <tina.zhang@intel.com>
> ---
>  include/uapi/linux/vfio.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 02bb7ad6e986..27300597717f 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -696,6 +696,18 @@ struct vfio_device_ioeventfd {
>  
>  #define VFIO_DEVICE_IOEVENTFD		_IO(VFIO_TYPE, VFIO_BASE + 16)
>  
> +/**
> + * VFIO_DEVICE_SET_GFX_FLIP_EVENTFD - _IOW(VFIO_TYPE, VFIO_BASE + 17, __s32)
> + *
> + * Set eventfd based signaling mechanism to deliver vGPU framebuffer page
> + * flip event to userspace. A value of -1 is used to stop the page flip
> + * delivering.
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +
> +#define VFIO_DEVICE_SET_GFX_FLIP_EVENTFD _IO(VFIO_TYPE, VFIO_BASE + 17)
> +
>  /* -------- API for Type1 VFIO IOMMU -------- */
>  
>  /**
> -- 
> 2.17.1
>
Gerd Hoffmann May 27, 2019, 12:22 p.m. UTC | #2
On Mon, May 27, 2019 at 05:07:41PM +0800, Zhenyu Wang wrote:
> On 2019.05.27 16:43:11 +0800, Tina Zhang wrote:
> > Add VFIO_DEVICE_SET_GFX_FLIP_EVENTFD ioctl command to set eventfd
> > based signaling mechanism to deliver vGPU framebuffer page flip
> > event to userspace.
> 
> Should we add probe to see if driver can support gfx flip event?

Userspace can simply call VFIO_DEVICE_SET_GFX_FLIP_EVENTFD and see if it
worked.  If so -> use the eventfd.  Otherwise take the fallback path
(timer based polling).  I can't see any advantage a separate feature
probe steps adds.

cheers,
  Gerd
Alex Williamson May 27, 2019, 2:04 p.m. UTC | #3
On Mon, 27 May 2019 16:43:11 +0800
Tina Zhang <tina.zhang@intel.com> wrote:

> Add VFIO_DEVICE_SET_GFX_FLIP_EVENTFD ioctl command to set eventfd
> based signaling mechanism to deliver vGPU framebuffer page flip
> event to userspace.
> 
> Signed-off-by: Tina Zhang <tina.zhang@intel.com>
> ---
>  include/uapi/linux/vfio.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 02bb7ad6e986..27300597717f 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -696,6 +696,18 @@ struct vfio_device_ioeventfd {
>  
>  #define VFIO_DEVICE_IOEVENTFD		_IO(VFIO_TYPE, VFIO_BASE + 16)
>  
> +/**
> + * VFIO_DEVICE_SET_GFX_FLIP_EVENTFD - _IOW(VFIO_TYPE, VFIO_BASE + 17, __s32)
> + *
> + * Set eventfd based signaling mechanism to deliver vGPU framebuffer page
> + * flip event to userspace. A value of -1 is used to stop the page flip
> + * delivering.
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +
> +#define VFIO_DEVICE_SET_GFX_FLIP_EVENTFD _IO(VFIO_TYPE, VFIO_BASE + 17)
> +
>  /* -------- API for Type1 VFIO IOMMU -------- */
>  
>  /**

Why can't we use VFIO_DEVICE_SET_IRQS for this?  We can add a
capability to vfio_irq_info in the same way that we did for regions to
describe device specific IRQ support.  Thanks,

Alex
Tina Zhang May 28, 2019, 1:42 a.m. UTC | #4
> -----Original Message-----
> From: intel-gvt-dev [mailto:intel-gvt-dev-bounces@lists.freedesktop.org] On
> Behalf Of Alex Williamson
> Sent: Monday, May 27, 2019 10:05 PM
> To: Zhang, Tina <tina.zhang@intel.com>
> Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org;
> zhenyuw@linux.intel.com; Yuan, Hang <hang.yuan@intel.com>;
> kraxel@redhat.com; intel-gvt-dev@lists.freedesktop.org; Lv, Zhiyuan
> <zhiyuan.lv@intel.com>
> Subject: Re: [PATCH 1/2] vfio: ABI for setting mdev display flip eventfd
> 
> On Mon, 27 May 2019 16:43:11 +0800
> Tina Zhang <tina.zhang@intel.com> wrote:
> 
> > Add VFIO_DEVICE_SET_GFX_FLIP_EVENTFD ioctl command to set eventfd
> > based signaling mechanism to deliver vGPU framebuffer page flip event
> > to userspace.
> >
> > Signed-off-by: Tina Zhang <tina.zhang@intel.com>
> > ---
> >  include/uapi/linux/vfio.h | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 02bb7ad6e986..27300597717f 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -696,6 +696,18 @@ struct vfio_device_ioeventfd {
> >
> >  #define VFIO_DEVICE_IOEVENTFD		_IO(VFIO_TYPE, VFIO_BASE +
> 16)
> >
> > +/**
> > + * VFIO_DEVICE_SET_GFX_FLIP_EVENTFD - _IOW(VFIO_TYPE, VFIO_BASE
> + 17,
> > +__s32)
> > + *
> > + * Set eventfd based signaling mechanism to deliver vGPU framebuffer
> > +page
> > + * flip event to userspace. A value of -1 is used to stop the page
> > +flip
> > + * delivering.
> > + *
> > + * Return: 0 on success, -errno on failure.
> > + */
> > +
> > +#define VFIO_DEVICE_SET_GFX_FLIP_EVENTFD _IO(VFIO_TYPE,
> VFIO_BASE +
> > +17)
> > +
> >  /* -------- API for Type1 VFIO IOMMU -------- */
> >
> >  /**
> 
> Why can't we use VFIO_DEVICE_SET_IRQS for this?  We can add a capability
> to vfio_irq_info in the same way that we did for regions to describe device
> specific IRQ support.  Thanks,
Add a new kind of index, like this?
enum {
        VFIO_PCI_INTX_IRQ_INDEX,
        VFIO_PCI_MSI_IRQ_INDEX,
        VFIO_PCI_MSIX_IRQ_INDEX,
        VFIO_PCI_ERR_IRQ_INDEX,
        VFIO_PCI_REQ_IRQ_INDEX,
+      VFIO_PCI_GFX_FLIP_EVENT_INDEX,
        VFIO_PCI_NUM_IRQS
};
Perhaps this is what we don't want. This VFIO_PCI_GFX_FLIP_EVENT_INDEX is specific to graphics card and it's actually an event which is reported by INTX/MSI/ MSIX IRQ.
Thanks.

BR,
Tina
> 
> Alex
> _______________________________________________
> intel-gvt-dev mailing list
> intel-gvt-dev@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev
Zhenyu Wang May 28, 2019, 2:51 a.m. UTC | #5
On 2019.05.27 14:22:37 +0200, Gerd Hoffmann wrote:
> On Mon, May 27, 2019 at 05:07:41PM +0800, Zhenyu Wang wrote:
> > On 2019.05.27 16:43:11 +0800, Tina Zhang wrote:
> > > Add VFIO_DEVICE_SET_GFX_FLIP_EVENTFD ioctl command to set eventfd
> > > based signaling mechanism to deliver vGPU framebuffer page flip
> > > event to userspace.
> > 
> > Should we add probe to see if driver can support gfx flip event?
> 
> Userspace can simply call VFIO_DEVICE_SET_GFX_FLIP_EVENTFD and see if it
> worked.  If so -> use the eventfd.  Otherwise take the fallback path
> (timer based polling).  I can't see any advantage a separate feature
> probe steps adds.
> 

Then we need to define error return which means driver doesn't support
e.g -ENOTTY, and driver shouldn't return that for other possible
failure, so user space won't get confused.

I think if we can define this as generic display event notification?
Not necessarily just for flip, just a display change notification to
let user space query current state.
Alex Williamson May 28, 2019, 4:18 a.m. UTC | #6
On Tue, 28 May 2019 01:42:57 +0000
"Zhang, Tina" <tina.zhang@intel.com> wrote:

> > -----Original Message-----
> > From: intel-gvt-dev [mailto:intel-gvt-dev-bounces@lists.freedesktop.org] On
> > Behalf Of Alex Williamson
> > Sent: Monday, May 27, 2019 10:05 PM
> > To: Zhang, Tina <tina.zhang@intel.com>
> > Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org;
> > zhenyuw@linux.intel.com; Yuan, Hang <hang.yuan@intel.com>;
> > kraxel@redhat.com; intel-gvt-dev@lists.freedesktop.org; Lv, Zhiyuan
> > <zhiyuan.lv@intel.com>
> > Subject: Re: [PATCH 1/2] vfio: ABI for setting mdev display flip eventfd
> > 
> > On Mon, 27 May 2019 16:43:11 +0800
> > Tina Zhang <tina.zhang@intel.com> wrote:
> >   
> > > Add VFIO_DEVICE_SET_GFX_FLIP_EVENTFD ioctl command to set eventfd
> > > based signaling mechanism to deliver vGPU framebuffer page flip event
> > > to userspace.
> > >
> > > Signed-off-by: Tina Zhang <tina.zhang@intel.com>
> > > ---
> > >  include/uapi/linux/vfio.h | 12 ++++++++++++
> > >  1 file changed, 12 insertions(+)
> > >
> > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > > index 02bb7ad6e986..27300597717f 100644
> > > --- a/include/uapi/linux/vfio.h
> > > +++ b/include/uapi/linux/vfio.h
> > > @@ -696,6 +696,18 @@ struct vfio_device_ioeventfd {
> > >
> > >  #define VFIO_DEVICE_IOEVENTFD		_IO(VFIO_TYPE, VFIO_BASE +  
> > 16)  
> > >
> > > +/**
> > > + * VFIO_DEVICE_SET_GFX_FLIP_EVENTFD - _IOW(VFIO_TYPE, VFIO_BASE  
> > + 17,  
> > > +__s32)
> > > + *
> > > + * Set eventfd based signaling mechanism to deliver vGPU framebuffer
> > > +page
> > > + * flip event to userspace. A value of -1 is used to stop the page
> > > +flip
> > > + * delivering.
> > > + *
> > > + * Return: 0 on success, -errno on failure.
> > > + */
> > > +
> > > +#define VFIO_DEVICE_SET_GFX_FLIP_EVENTFD _IO(VFIO_TYPE,  
> > VFIO_BASE +  
> > > +17)
> > > +
> > >  /* -------- API for Type1 VFIO IOMMU -------- */
> > >
> > >  /**  
> > 
> > Why can't we use VFIO_DEVICE_SET_IRQS for this?  We can add a capability
> > to vfio_irq_info in the same way that we did for regions to describe device
> > specific IRQ support.  Thanks,  
> Add a new kind of index, like this?
> enum {
>         VFIO_PCI_INTX_IRQ_INDEX,
>         VFIO_PCI_MSI_IRQ_INDEX,
>         VFIO_PCI_MSIX_IRQ_INDEX,
>         VFIO_PCI_ERR_IRQ_INDEX,
>         VFIO_PCI_REQ_IRQ_INDEX,
> +      VFIO_PCI_GFX_FLIP_EVENT_INDEX,
>         VFIO_PCI_NUM_IRQS
> };
> Perhaps this is what we don't want. This
> VFIO_PCI_GFX_FLIP_EVENT_INDEX is specific to graphics card and it's
> actually an event which is reported by INTX/MSI/ MSIX IRQ. Thanks.

Right, that is not what I'm suggesting.  What I'm looking for is a
similar conversion to what we did for regions, where we extended the
data returned in GET_REGION_INFO to include capabilities
(c84982adb23b), capped the number of regions we define with fixed
indexes (c7bb4cb40f89), and added device specific regions, such as IGD
OpRegion (5846ff54e87d) and IGD host and LPC bridges (f572a960a15e).
The same thing should happen here, the current value of
VFIO_PCI_NUM_IRQS becomes fixed and part of the vfio-pci ABI,
vfio_irq_info is extended with capability support following the same
mechanism, headers, and helpers we use for regions, then the mdev device
simply exposes the extended (and backwards compatible) API without
requiring a device specific ioctl.  Thanks,

Alex

Patch
diff mbox series

diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 02bb7ad6e986..27300597717f 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -696,6 +696,18 @@  struct vfio_device_ioeventfd {
 
 #define VFIO_DEVICE_IOEVENTFD		_IO(VFIO_TYPE, VFIO_BASE + 16)
 
+/**
+ * VFIO_DEVICE_SET_GFX_FLIP_EVENTFD - _IOW(VFIO_TYPE, VFIO_BASE + 17, __s32)
+ *
+ * Set eventfd based signaling mechanism to deliver vGPU framebuffer page
+ * flip event to userspace. A value of -1 is used to stop the page flip
+ * delivering.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
+
+#define VFIO_DEVICE_SET_GFX_FLIP_EVENTFD _IO(VFIO_TYPE, VFIO_BASE + 17)
+
 /* -------- API for Type1 VFIO IOMMU -------- */
 
 /**