[PATCH] drm/i915/gvt: Fix kernel oops for 3-level ppgtt guest
Zhenyu Wang
zhenyuw at linux.intel.com
Fri May 8 11:50:18 UTC 2020
On 2020.05.08 11:13:38 +0000, Zhang, Xiong Y wrote:
> > -----Original Message-----
> > From: intel-gvt-dev <intel-gvt-dev-bounces at lists.freedesktop.org> On Behalf
> > Of Zhenyu Wang
> > Sent: Wednesday, May 6, 2020 5:59 PM
> > To: intel-gvt-dev at lists.freedesktop.org
> > Subject: [PATCH] drm/i915/gvt: Fix kernel oops for 3-level ppgtt guest
> >
> > As i915 won't allocate extra PDP for current default PML4 table, so for 3-level
> > ppgtt guest, we would hit kernel pointer access failure on extra PDP pointers.
> > So this trys to bypass that now.
> > It won't impact real shadow PPGTT setup, so guest context still works.
> >
> > This is verified on 4.15 guest kernel with i915.enable_ppgtt=1 to force on old
> > aliasing ppgtt behavior.
> >
> > Fixes: 4f15665ccbba ("drm/i915: Add ppgtt to GVT GEM context")
> > Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
> > ---
> > drivers/gpu/drm/i915/gvt/scheduler.c | 6 +++++-
> > 1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c
> > b/drivers/gpu/drm/i915/gvt/scheduler.c
> > index 9c3558489d17..6ab1d95c1fae 100644
> > --- a/drivers/gpu/drm/i915/gvt/scheduler.c
> > +++ b/drivers/gpu/drm/i915/gvt/scheduler.c
> > @@ -420,7 +420,11 @@ static void set_context_ppgtt_from_shadow(struct
> > intel_vgpu_workload *workload,
> > for (i = 0; i < GVT_RING_CTX_NR_PDPS; i++) {
> > struct i915_page_directory * const pd =
> > i915_pd_entry(ppgtt->pd, i);
> > -
> > + /* skip now as current i915 ppgtt alloc won't allocate
> > + top level pdp for non 4-level table, won't impact
> > + shadow ppgtt. */
> > + if (!pd)
> > + break;
> [Zhang, Xiong Y] does it exist in older kernel only ? current staging code allocate 4 pdp for non 4-level table.
But in all current case we'll only allocate for pml4 as it checks hw info.
> I915_context_ppgtt_root_restore() have the same issue, it should be modified also.
yeah, missed that although not shown in my test..
> > px_dma(pd) = mm->ppgtt_mm.shadow_pdps[i];
> > }
> > }
> > --
> > 2.26.2
> >
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> > intel-gvt-dev at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev
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