[PATCH] drm/i915/gvt: Enable gvt debugfs with mmio comparison on all vGPUs.

[Zhenyu Wang]

On 2018.06.07 15:56:08 +0800, Colin Xu wrote:
> On 06/06/2018 11:31 AM, Zhenyu Wang wrote:
> > On 2018.06.05 16:41:14 +0800, Colin Xu wrote:
> > > On 06/05/2018 03:23 PM, Zhenyu Wang wrote:
> > > > On 2018.06.04 16:47:20 +0800, Colin Xu wrote:
> > > > > Current mmio_diff_handler can only compare 1 active vGPU with host.
> > > > > 
> > > > > The patch will extend the mmio comparison debugfs capability to all
> > > > > active vGPUs, selected by vGPU mask bits.
> > > > >     - Add mmio_compare_vgpu_mask to enable vGPU selection.
> > > > >       - Bit 0: select all active vGPU.
> > > > >       - Bit i: select vGPU id i.
> > > > >     - Add mmio_compare to show comparison result.
> > > > >     - Retive mmio_diff since it's functionality is inherited and enhanced.
> > > > > 
> > > > > The new headline of the comparision results is:
> > > > > +---+--------+----+--------+--------+-----+
> > > > > | * | Offset | HW | vGPU i | vGPU j | ... |
> > > > > +---+--------+----+--------+--------+-----+
> > > > > 
> > > > > The leading star of each line indicate diff between preg and vreg(s).
> > > > > When only 1 vGPU is selected, per-bits-diff will append to each line.
> > > > > 
> > > > > Sample output:
> > > > > 
> > > > > - 1 vGPU, debugfs_vgpu_mask is 0x1 or 0x2:
> > > > > * Offset   HW       vGPU   1 Diff-Bits
> > > > >     0000003c 00000000 00000000
> > > > > * 00002030 00000ad8 00000000 3-4,6-7,9,11
> > > > > 
> > > > > - 3 vGPUs, debugfs_vgpu_mask is 0x1:
> > > > > * Offset   HW       vGPU   1 vGPU   2 vGPU   3
> > > > >     0000003c 00000000 00000000 00000000 00000000
> > > > > * 00002074 002012d0 0000cce8 00000000 00013b20
> > > > > 
> > > > > - 3 vGPUs, debugfs_vgpu_mask is 0xa:
> > > > > * Offset   HW       vGPU   1 vGPU   3
> > > > >     0000003c 00000000 00000000 00000000
> > > > > * 00002074 0000be30 0000d040 00013b20
> > > > > 
> > > > Current mmio_diff is per-vgpu so you already have all info. So you
> > > > can use current mmio_diff to compare between vGPUs if you want. I
> > > > don't see a must to change this for kernel interface.
> > > > 
> > > Yes it's an enhancement instead of a "must change".
> > > However in some scenarioes the enhancement could do better:
> > > - Current mmio_diff only shows diff but omit "match". When compare across
> > >    vGPU's, the result won't match on offset since the diff offsets will be
> > >    different. The limit could be removed by uncheck prev vs. vreg diff in
> > >    current mmio_diff by the way.
> > > - Dump separately diffs from dump at the same time. Which may be useful
> > >    in the case that we need dump vGPU's and host's status at the same time.
> > > 
> > > The main purpose is to keep a code snippet to bring convenience for future
> > > debug. Hope it will help someone in future no matter it's merged or not.
> > > 
> > Then instead of removing current mmio_diff file, you can create
> > new debugfs helper for that. As you said they could be used for
> > different case and possible to re-use current mmio diff code somehow.
> 
> The new help function and struct define share most of mmio_diff structure define
> with some difference and addition. When only 1 vGPU selected, the new
> help function do almost the same as current mmio_diff, except that it also shows
> mmio value that preg equals to vreg, while mmio_diff only show mmio at
> different value.
> So it seems keep them both will have some shared parts in both definition and
> capability.
> 
> Maybe it's better I don't have to rename mmio_diff, just enhance under current
> naming?
> 

yeah, you can extend mmio_diff if needed and provide new coalescing interface.

-- 
Open Source Technology Center, Intel ltd.

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