[Intel-gfx] [PATCH v2 2/2] drm/i915: enable to read CSB and CSB write pointer from HWSP in GVT-g VM

[Joonas Lahtinen]

On Mon, 2017-10-02 at 11:23 +0100, Chris Wilson wrote:
> Quoting Joonas Lahtinen (2017-10-02 11:03:30)
> > On Sat, 2017-09-30 at 13:57 +0800, Weinan Li wrote:
> > > Let GVT-g VM read the CSB and CSB write pointer from virtual HWSP, not all
> > > the host support this feature, need to check the BIT(3) of caps in PVINFO.
> > > 
> > > Signed-off-by: Weinan Li <weinan.z.li at intel.com>
> > > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > 
> > <SNIP>
> > 
> > > @@ -396,6 +393,12 @@ static bool csb_force_mmio(struct drm_i915_private *i915)
> > >       if (intel_vtd_active())
> > >               return true;
> > >  
> > > +     /* GVT emulation depends upon host kernel implementation, check
> > > +      * support capbility by reading PV INFO before access HWSP.
> > > +      */
> > 
> > The comment can be dropped completely, the code is self-descriptive.
> > 
> > > +++ b/drivers/gpu/drm/i915/intel_lrc.c
> > > @@ -722,7 +722,12 @@ static void intel_lrc_irq_handler(unsigned long data)
> > >                       &engine->status_page.page_addr[I915_HWS_CSB_BUF0_INDEX];
> > >               unsigned int head, tail;
> > >  
> > > -             /* However GVT emulation depends upon intercepting CSB mmio */
> > > +             /* However GVT-g emulation depends upon host kernel
> > > +              * implementation, need to check support capbility by reading PV
> > > +              * INFO before access HWSP. Beside from this, another special
> > > +              * configuration may also need to force use mmio, like IOMMU
> > > +              * enabled.
> > > +              */
> > 
> > s/capbility/capability/ and please rephrase this to be a kerneldoc for
> > csb_use_mmio at the declaration.
> 
> This is not a description of how to use the function or even on how
> csb_use_mmio work, this is why we want certain logic paths. Just a regular
> old comment.

That's why I asked to "rephrase" :) Anyway, it seems like there already
is kerneldoc for the csb_use_mmio, so this comment can be dropped.

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation