[Intel-gfx] [PATCH v8 2/9] drm/i915: vgpu shared memory setup for pv optimization

[Chris Wilson]

Quoting Xiaolin Zhang (2019-07-23 12:31:57)
> To enable vgpu pv features, we need to setup a shared memory page
> which will be used for data exchange directly accessed between both
> guest and backend i915 driver to avoid emulation trap cost.
> 
> guest i915 will allocate this page memory and then pass it's physical
> address to backend i915 driver through PVINFO register so that backend i915
> driver can access this shared page meory without any trap cost with the
> help form hyperviser's read guest gpa functionality.
> 
> guest i915 will send VGT_G2V_SHARED_PAGE_SETUP notification to host GVT
> once shared memory setup finished.
> 
> the layout of the shared_page also defined as well in this patch which
> is used for pv features implementation.
> 
> v0: RFC.
> v1: addressed RFC comment to move both shared_page_lock and shared_page
> to i915_virtual_gpu structure.
> v2: packed i915_virtual_gpu structure.
> v3: added SHARED_PAGE_SETUP g2v notification for pv shared_page setup
> v4: added intel_vgpu_setup_shared_page() in i915_vgpu_pv.c.
> v5: per engine desc data in shared memory.
> v6: added version support in shared memory (Zhenyu).
> v7: rebase.
> 
> Signed-off-by: Xiaolin Zhang <xiaolin.zhang at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h    |  4 +-
>  drivers/gpu/drm/i915/i915_pvinfo.h |  5 ++-
>  drivers/gpu/drm/i915/i915_vgpu.c   | 85 ++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/i915_vgpu.h   | 17 ++++++++
>  4 files changed, 109 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index fa5dc47..48cf141 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1080,7 +1080,9 @@ struct i915_virtual_gpu {
>         bool active;
>         u32 caps;
>         u32 pv_caps;
> -};
> +
> +       struct i915_virtual_gpu_pv *pv;
> +} __packed;
>  
>  /* used in computing the new watermarks state */
>  struct intel_wm_config {
> diff --git a/drivers/gpu/drm/i915/i915_pvinfo.h b/drivers/gpu/drm/i915/i915_pvinfo.h
> index ad398b4..3c63603 100644
> --- a/drivers/gpu/drm/i915/i915_pvinfo.h
> +++ b/drivers/gpu/drm/i915/i915_pvinfo.h
> @@ -48,6 +48,7 @@ enum vgt_g2v_type {
>         VGT_G2V_PPGTT_L4_PAGE_TABLE_DESTROY,
>         VGT_G2V_EXECLIST_CONTEXT_CREATE,
>         VGT_G2V_EXECLIST_CONTEXT_DESTROY,
> +       VGT_G2V_SHARED_PAGE_SETUP,
>         VGT_G2V_MAX,
>  };
>  
> @@ -112,7 +113,9 @@ struct vgt_if {
>  
>         u32 pv_caps;
>  
> -       u32  rsv7[0x200 - 25];    /* pad to one page */
> +       u64 shared_page_gpa;
> +
> +       u32  rsv7[0x200 - 27];    /* pad to one page */
>  } __packed;
>  
>  #define vgtif_offset(x) (offsetof(struct vgt_if, x))
> diff --git a/drivers/gpu/drm/i915/i915_vgpu.c b/drivers/gpu/drm/i915/i915_vgpu.c
> index 9b37dd1..998cf6a 100644
> --- a/drivers/gpu/drm/i915/i915_vgpu.c
> +++ b/drivers/gpu/drm/i915/i915_vgpu.c
> @@ -145,6 +145,7 @@ static void vgt_deballoon_space(struct i915_ggtt *ggtt,
>   */
>  void intel_vgt_deballoon(struct i915_ggtt *ggtt)

This addendum is nothing to do with the i915_ggtt cleanup.

>  {
> +       struct drm_i915_private *i915 = ggtt->vm.i915;
>         int i;
>  
>         if (!intel_vgpu_active(ggtt->vm.i915))
> @@ -154,6 +155,9 @@ void intel_vgt_deballoon(struct i915_ggtt *ggtt)
>  
>         for (i = 0; i < 4; i++)
>                 vgt_deballoon_space(ggtt, &bl_info.space[i]);
> +
> +       if (i915->vgpu.pv)
> +               free_page((unsigned long)i915->vgpu.pv->shared_page);

__free_page(shared_page);

>  }
>  
>  static int vgt_balloon_space(struct i915_ggtt *ggtt,
> @@ -309,6 +313,81 @@ int intel_vgt_balloon(struct i915_ggtt *ggtt)
>   * i915 vgpu PV support for Linux
>   */
>  
> +/*
> + * shared_page setup for VGPU PV features
> + */
> +static int intel_vgpu_setup_shared_page(struct drm_i915_private *dev_priv,
> +               void __iomem *shared_area)
> +{
> +       void __iomem *addr;
> +       struct i915_virtual_gpu_pv *pv;
> +       struct gvt_shared_page *base;
> +       u64 gpa;
> +       u16 ver_maj, ver_min;
> +
> +       /* We allocate 1 page shared between guest and GVT for data exchange.
> +        *       ___________.....................
> +        *      |head       |                   |
> +        *      |___________|.................. PAGE/8
> +        *      |PV ELSP                        |
> +        *      :___________....................PAGE/4
> +        *      |desc (SEND)                    |
> +        *      |                               |
> +        *      :_______________________________PAGE/2
> +        *      |cmds (SEND)                    |
> +        *      |                               |
> +        *      |                               |
> +        *      |                               |
> +        *      |                               |
> +        *      |_______________________________|
> +        *
> +        * 0 offset: PV version area
> +        * PAGE/8 offset: per engine workload submission data area
> +        * PAGE/4 offset: PV command buffer command descriptor area
> +        * PAGE/2 offset: PV command buffer command data area
> +        */
> +
> +       base =  (struct gvt_shared_page *)get_zeroed_page(GFP_KERNEL);
> +       if (!base) {
> +               DRM_INFO("out of memory for shared page memory\n");

DRM_INFO is for providing the user with useful information; not dropping
debug messages. If you do want to address the user, I'd recommend
dev_info
-Chris