[PATCH 2/2] drm/i915/gen7: Clear all EU/L3 residual contexts

[Joonas Lahtinen]

Quoting Akeem G Abodunrin (2020-01-30 18:57:21)
> From: Prathap Kumar Valsan <prathap.kumar.valsan at intel.com>
> 
> On gen7 and gen7.5 devices, there could be leftover data residuals in
> EU/L3 from the retiring context. This patch introduces workaround to clear
> that residual contexts, by submitting a batch buffer with dedicated HW
> context to the GPU with ring allocation for each context switching.
> 
> This security mitigation change does not trigger any performance
> regression. Performance is on par with current mainline/drm-tip.
> 
> Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Signed-off-by: Prathap Kumar Valsan <prathap.kumar.valsan at intel.com>
> Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin at intel.com>
> Cc: Chris Wilson <chris.p.wilson at intel.com>
> Cc: Balestrieri Francesco <francesco.balestrieri at intel.com>
> Cc: Bloomfield Jon <jon.bloomfield at intel.com>
> Cc: Dutt Sudeep <sudeep.dutt at intel.com>
> ---
>  drivers/gpu/drm/i915/Makefile                 |   1 +
>  drivers/gpu/drm/i915/gt/gen7_renderclear.c    | 535 ++++++++++++++++++
>  drivers/gpu/drm/i915/gt/gen7_renderclear.h    |  15 +
>  drivers/gpu/drm/i915/gt/intel_gpu_commands.h  |  17 +-
>  .../gpu/drm/i915/gt/intel_ring_submission.c   |   3 +-
>  drivers/gpu/drm/i915/i915_utils.h             |   5 +
>  6 files changed, 572 insertions(+), 4 deletions(-)
>  create mode 100644 drivers/gpu/drm/i915/gt/gen7_renderclear.c
>  create mode 100644 drivers/gpu/drm/i915/gt/gen7_renderclear.h
> 
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index 3c88d7d8c764..f96bae664a03 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -78,6 +78,7 @@ gt-y += \
>         gt/debugfs_gt.o \
>         gt/debugfs_gt_pm.o \
>         gt/gen6_ppgtt.o \
> +       gt/gen7_renderclear.o \
>         gt/gen8_ppgtt.o \
>         gt/intel_breadcrumbs.o \
>         gt/intel_context.o \
> diff --git a/drivers/gpu/drm/i915/gt/gen7_renderclear.c b/drivers/gpu/drm/i915/gt/gen7_renderclear.c
> new file mode 100644
> index 000000000000..a6f5f1602e33
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/gt/gen7_renderclear.c
> @@ -0,0 +1,535 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2019 Intel Corporation
> + */
> +
> +#include "gen7_renderclear.h"
> +#include "i915_drv.h"
> +#include "i915_utils.h"
> +#include "intel_gpu_commands.h"
> +
> +#define MAX_URB_ENTRIES 64
> +#define STATE_SIZE (4 * 1024)
> +#define GT3_INLINE_DATA_DELAYS 0x1E00
> +#define batch_advance(Y, CS) GEM_BUG_ON((Y)->end != (CS))
> +
> +/*
> + * Media CB Kernel for gen7 devices
> + * TODO: Add comments to kernel, indicating what each array of hex does or
> + * include header file, which has assembly source and support in igt to be
> + * able to generate kernel in this same format
> + */

Having the original source code for the kernels in IGT is the
best way to proceed. The kernels should also be split into
separate files which can be generated from IGT and copied
over as-is for easy verification.

Regards, Joonas