Userspace may leave predication enabled upon return from the batch
buffer, which has the consequent of preventing all operation from the
ring from being executed, including all the synchronisation, coherency
control, arbitration and user signaling. This is more than just a local
gpu hang in one client, as the user has the ability to prevent the
kernel from applying critical workarounds and can cause a full GT reset.
We could simply execute MI_SET_PREDICATE upon return from the user
batch, but this has the repercussion of modifying the user's context
state. Instead, we opt to execute a fixup batch which by mixing
predicated operations can determine the state of the
SET_PREDICATE_RESULT register and restore it prior to the next userspace
batch. This allows us to protect the kernel's ring without changing the
uABI.
Suggested-by: Zbigniew Kempczynski <zbigniew.kempczynski@intel.com>
Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
Cc: Zbigniew Kempczynski <zbigniew.kempczynski@intel.com>
Cc: Thomas Hellstrom <thomas.hellstrom@intel.com>
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220425152317.4275-4-ramalingam.c@intel.com
These SFC registers were defined in an unusual way, taking an engine as
a parameter rather than an engine MMIO base offset. Let's adjust them
to match the style used by other per-engine registers and move them to
intel_engine_regs.h.
While doing this move, we can drop GEN12_HCP_SFC_FORCED_LOCK completely;
it was intended for use in an early version of a hardware workaround,
but was no longer necessary by the time the workaround was finalized.
It is not used anywhere in the driver.
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Atwood <matthew.s.atwood@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220209051140.1599643-3-matthew.d.roper@intel.com
The various MI_PREDICATE registers have per-engine instances. Today we
only utilize the RCS0 instance of each, but that will likely change in
the future; switch to parameterized register definitions to make these
easier to work with going forward.
Of special note is MI_PREDICATE_RESULT_2; we only use it in one place in
the driver today in HSW-specific code. It turns out that the bspec
(page 94) lists two different offsets for this register on HSW; one is
in the standard location shared by all other platforms (base + 0x3bc)
and the other is an unusual location (0x2214). We're using the second,
non-standard offset in i915 today; that offset doesn't exist on any
other platforms (and it's not even 100% clear that it's correct for HSW)
so I've renamed the current non-standard definition to
HSW_MI_PREDICATE_RESULT_2; the new cross-platform parameterized macro
(which is still unused at the moment) uses the standard offset.
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220127234334.4016964-5-matthew.d.roper@intel.com
