Being able to program OACONTROL from a non-privileged batch buffer is not sufficient to be able to configure the OA unit. This was originally allowed to help enable Mesa to expose OA counters via the INTEL_performance_query extension, but the current implementation based on programming OACONTROL via a batch buffer isn't able to report useable data without a more complete OA unit configuration. Mesa handles the possibility that writes to OACONTROL may not be allowed and so only advertises the extension after explicitly testing that a write to OACONTROL succeeds. Based on this; removing OACONTROL from the whitelist should be ok for userspace.
Removing this simplifies adding a new kernel api for configuring the OA unit without needing to consider the possibility that userspace might trample on OACONTROL state which we'd like to start managing within the kernel instead. In particular running any Mesa based GL application currently results in clearing OACONTROL when initializing which would disable the capturing of metrics.
XXX: actually since rebasing this on a recent nightly this patch does seem to be breaking gnome-shell on mesa-11.1 - it's not clear a.t.m why the change didn't seem to cause a problem based on v4.5 with the same gnome-shell/mesa versions.
Signed-off-by: Robert Bragg robert@sixbynine.org --- drivers/gpu/drm/i915/i915_cmd_parser.c | 33 ++------------------------------- 1 file changed, 2 insertions(+), 31 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c index 035f2dd..8d323b9 100644 --- a/drivers/gpu/drm/i915/i915_cmd_parser.c +++ b/drivers/gpu/drm/i915/i915_cmd_parser.c @@ -445,7 +445,6 @@ static const struct drm_i915_reg_descriptor gen7_render_regs[] = { REG64(PS_INVOCATION_COUNT), REG64(PS_DEPTH_COUNT), REG64_IDX(RING_TIMESTAMP, RENDER_RING_BASE), - REG32(GEN7_OACONTROL), /* Only allowed for LRI and SRM. See below. */ REG64(MI_PREDICATE_SRC0), REG64(MI_PREDICATE_SRC1), REG32(GEN7_3DPRIM_END_OFFSET), @@ -1044,8 +1043,7 @@ bool i915_needs_cmd_parser(struct intel_engine_cs *engine) static bool check_cmd(const struct intel_engine_cs *engine, const struct drm_i915_cmd_descriptor *desc, const u32 *cmd, u32 length, - const bool is_master, - bool *oacontrol_set) + const bool is_master) { if (desc->flags & CMD_DESC_REJECT) { DRM_DEBUG_DRIVER("CMD: Rejected command: 0x%08X\n", *cmd); @@ -1083,26 +1081,6 @@ static bool check_cmd(const struct intel_engine_cs *engine, }
/* - * OACONTROL requires some special handling for - * writes. We want to make sure that any batch which - * enables OA also disables it before the end of the - * batch. The goal is to prevent one process from - * snooping on the perf data from another process. To do - * that, we need to check the value that will be written - * to the register. Hence, limit OACONTROL writes to - * only MI_LOAD_REGISTER_IMM commands. - */ - if (reg_addr == i915_mmio_reg_offset(GEN7_OACONTROL)) { - if (desc->cmd.value == MI_LOAD_REGISTER_MEM) { - DRM_DEBUG_DRIVER("CMD: Rejected LRM to OACONTROL\n"); - return false; - } - - if (desc->cmd.value == MI_LOAD_REGISTER_IMM(1)) - *oacontrol_set = (cmd[offset + 1] != 0); - } - - /* * Check the value written to the register against the * allowed mask/value pair given in the whitelist entry. */ @@ -1186,7 +1164,6 @@ int i915_parse_cmds(struct intel_engine_cs *engine, { u32 *cmd, *batch_base, *batch_end; struct drm_i915_cmd_descriptor default_desc = { 0 }; - bool oacontrol_set = false; /* OACONTROL tracking. See check_cmd() */ int ret = 0;
batch_base = copy_batch(shadow_batch_obj, batch_obj, @@ -1243,8 +1220,7 @@ int i915_parse_cmds(struct intel_engine_cs *engine, break; }
- if (!check_cmd(engine, desc, cmd, length, is_master, - &oacontrol_set)) { + if (!check_cmd(engine, desc, cmd, length, is_master)) { ret = -EINVAL; break; } @@ -1252,11 +1228,6 @@ int i915_parse_cmds(struct intel_engine_cs *engine, cmd += length; }
- if (oacontrol_set) { - DRM_DEBUG_DRIVER("CMD: batch set OACONTROL but did not clear it\n"); - ret = -EINVAL; - } - if (cmd >= batch_end) { DRM_DEBUG_DRIVER("CMD: Got to the end of the buffer w/o a BBE cmd!\n"); ret = -EINVAL;