This fixes two different classes of bugs in the Intel graphics hardware:
MMIO register read hang:
"On Intels Gen8 and Gen9 Graphics hardware, a read of specific graphics
MMIO registers when the product is in certain low power states causes
a system hang.
There are two potential triggers for DoS:
a) H/W corruption of the RC6 save/restore vector
b) Hard hang within the MIPI hardware
This prevents the DoS in two areas of the hardware:
1) Detect corruption of RC6 address on exit from low-power state,
and if we find it corrupted, disable RC6 and RPM
2) Permanently lower the MIPI MMIO timeout"
Blitter command streamer unrestricted memory accesses:
"On Intels Gen9 Graphics hardware the Blitter Command Streamer (BCS)
allows writing to Memory Mapped Input Output (MMIO) that should be
blocked. With modifications of page tables, this can lead to privilege
escalation. This exposure is limited to the Guest Physical Address
space and does not allow for access outside of the graphics virtual
machine.
This series establishes a software parser into the Blitter command
stream to scan for, and prevent, reads or writes to MMIO's that should
not be accessible to non-privileged contexts.
Much of the command parser infrastructure has existed for some time,
and is used on Ivybridge/Haswell/Valleyview derived products to allow
the use of features normally blocked by hardware. In this legacy
context, the command parser is employed to allow normally unprivileged
submissions to be run with elevated privileges in order to grant
access to a limited set of extra capabilities. In this mode the parser
is optional; In the event that the parser finds any construct that it
cannot properly validate (e.g. nested command buffers), it simply
aborts the scan and submits the buffer in non-privileged mode.
For Gen9 Graphics, this series makes the parser mandatory for all
Blitter submissions. The incoming user buffer is first copied to a
kernel owned buffer, and parsed. If all checks are successful the
kernel owned buffer is mapped READ-ONLY and submitted on behalf of the
user. If any checks fail, or the parser is unable to complete the scan
(nested buffers), it is forcibly rejected. The successfully scanned
buffer is executed with NORMAL user privileges (key difference from
legacy usage).
Modern usermode does not use the Blitter on later hardware, having
switched over to using the 3D engine instead for performance reasons.
There are however some legacy usermode apps that rely on Blitter,
notably the SNA X-Server. There are no known usermode applications
that require nested command buffers on the Blitter, so the forcible
rejection of such buffers in this patch series is considered an
acceptable limitation"
* Intel graphics fixes in emailed bundle from Jon Bloomfield <jon.bloomfield@intel.com>:
drm/i915/cmdparser: Fix jump whitelist clearing
drm/i915/gen8+: Add RC6 CTX corruption WA
drm/i915: Lower RM timeout to avoid DSI hard hangs
drm/i915/cmdparser: Ignore Length operands during command matching
drm/i915/cmdparser: Add support for backward jumps
drm/i915/cmdparser: Use explicit goto for error paths
drm/i915: Add gen9 BCS cmdparsing
drm/i915: Allow parsing of unsized batches
drm/i915: Support ro ppgtt mapped cmdparser shadow buffers
drm/i915: Add support for mandatory cmdparsing
drm/i915: Remove Master tables from cmdparser
drm/i915: Disable Secure Batches for gen6+
drm/i915: Rename gen7 cmdparser tables
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