Re: [PATCH v3 3/8] drm/i915: Partition the fence registers for vGPU in i915 driver

Tian, Kevin
2014-12-17T04:58:43Z

> From: Tvrtko Ursulin
> Sent: Tuesday, December 16, 2014 9:44 PM
>
>
> On 12/16/2014 01:32 PM, Yu, Zhang wrote:
> > On 12/12/2014 9:07 PM, Tvrtko Ursulin wrote:
> >> On 11/13/2014 12:02 PM, Yu Zhang wrote:
> >>> With Intel GVT-g, the fence registers are partitioned by multiple
> >>> vGPU instances in different VMs. Routine i915_gem_load() is modified
> >>> to reset the num_fence_regs, when the driver detects it's running in
> >>> a VM. And the allocated fence number is provided in PV INFO page
> >>> structure.
> >>>
> >>> Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
> >>> Signed-off-by: Jike Song <jike.song@intel.com>
> >>> Signed-off-by: Eddie Dong <eddie.dong@intel.com>
> >>> ---
> >>> drivers/gpu/drm/i915/i915_gem.c | 5 +++++
> >>> 1 file changed, 5 insertions(+)
> >>>
> >>> diff --git a/drivers/gpu/drm/i915/i915_gem.c
> >>> b/drivers/gpu/drm/i915/i915_gem.c
> >>> index 1de94cc..0c8b32e 100644
> >>> --- a/drivers/gpu/drm/i915/i915_gem.c
> >>> +++ b/drivers/gpu/drm/i915/i915_gem.c
> >>> @@ -29,6 +29,7 @@
> >>> #include <drm/drm_vma_manager.h>
> >>> #include <drm/i915_drm.h>
> >>> #include "i915_drv.h"
> >>> +#include "i915_vgpu.h"
> >>> #include "i915_trace.h"
> >>> #include "intel_drv.h"
> >>> #include <linux/oom.h>
> >>> @@ -5014,6 +5015,10 @@ i915_gem_load(struct drm_device *dev)
> >>> else
> >>> dev_priv->num_fence_regs = 8;
> >>>
> >>> + if (intel_vgpu_active(dev))
> >>> + dev_priv->num_fence_regs =
> >>> + I915_READ(vgtif_reg(avail_rs.fence_num));
> >>> +
> >>> /* Initialize fence registers to zero */
> >>> INIT_LIST_HEAD(&dev_priv->mm.fence_list);
> >>> i915_gem_restore_fences(dev);
> >>>
> >>
> >> You don't need a start offset and number of allocated fences per domain?
> > The PV INFO structure is shared between each vgpu and host, so I guess
> > this is per domain?
> > Not sure if I get your exact meaning. :)
>
> I didn't figure out how each domain knowns which fences to use? They
> know how many, but which ones?
>

the offset is maintained in the host side, which will be added to guest index
in relevant emulation path.

Thanks
Kevin