[PATCH] drm/i915/gvt: Fix kernel oops for 3-level ppgtt guest
Zhang, Xiong Y
xiong.y.zhang at intel.com
Fri May 8 11:13:38 UTC 2020
> -----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.
I915_context_ppgtt_root_restore() have the same issue, it should be modified also.
thanks
> px_dma(pd) = mm->ppgtt_mm.shadow_pdps[i];
> }
> }
> --
> 2.26.2
>
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