From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> commit 984cadea032b103c5824a5f29d0a36b3e9df6333 upstream. The clear-residuals mitigation is a relatively heavy hammer and under some circumstances the user may wish to forgo the context isolation in order to meet some performance requirement. Introduce a generic module parameter to allow selectively enabling/disabling different mitigations. To disable just the clear-residuals mitigation (on Ivybridge, Baytrail, or Haswell) use the module parameter: i915.mitigations=auto,!residuals Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1858 Fixes: 47f8253d2b89 ("drm/i915/gen7: Clear all EU/L3 residual contexts") Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> Cc: Jon Bloomfield <jon.bloomfield@xxxxxxxxx> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx # v5.7 Reviewed-by: Jon Bloomfield <jon.bloomfield@xxxxxxxxx> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20210111225220.3483-3-chris@xxxxxxxxxxxxxxxxxx (cherry picked from commit f7452c7cbd5b5dfb9a6c84cb20bea04c89be50cd) Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/i915/Makefile | 1 drivers/gpu/drm/i915/gt/intel_ring_submission.c | 4 drivers/gpu/drm/i915/i915_mitigations.c | 146 ++++++++++++++++++++++++ drivers/gpu/drm/i915/i915_mitigations.h | 13 ++ 4 files changed, 163 insertions(+), 1 deletion(-) --- a/drivers/gpu/drm/i915/Makefile +++ b/drivers/gpu/drm/i915/Makefile @@ -38,6 +38,7 @@ i915-y += i915_drv.o \ i915_config.o \ i915_irq.o \ i915_getparam.o \ + i915_mitigations.o \ i915_params.o \ i915_pci.o \ i915_scatterlist.o \ --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c @@ -32,6 +32,7 @@ #include "gen6_ppgtt.h" #include "gen7_renderclear.h" #include "i915_drv.h" +#include "i915_mitigations.h" #include "intel_breadcrumbs.h" #include "intel_context.h" #include "intel_gt.h" @@ -885,7 +886,8 @@ static int switch_context(struct i915_re GEM_BUG_ON(HAS_EXECLISTS(engine->i915)); if (engine->wa_ctx.vma && ce != engine->kernel_context) { - if (engine->wa_ctx.vma->private != ce) { + if (engine->wa_ctx.vma->private != ce && + i915_mitigate_clear_residuals()) { ret = clear_residuals(rq); if (ret) return ret; --- /dev/null +++ b/drivers/gpu/drm/i915/i915_mitigations.c @@ -0,0 +1,146 @@ +// SPDX-License-Identifier: MIT +/* + * Copyright © 2021 Intel Corporation + */ + +#include <linux/kernel.h> +#include <linux/moduleparam.h> +#include <linux/slab.h> +#include <linux/string.h> + +#include "i915_drv.h" +#include "i915_mitigations.h" + +static unsigned long mitigations __read_mostly = ~0UL; + +enum { + CLEAR_RESIDUALS = 0, +}; + +static const char * const names[] = { + [CLEAR_RESIDUALS] = "residuals", +}; + +bool i915_mitigate_clear_residuals(void) +{ + return READ_ONCE(mitigations) & BIT(CLEAR_RESIDUALS); +} + +static int mitigations_set(const char *val, const struct kernel_param *kp) +{ + unsigned long new = ~0UL; + char *str, *sep, *tok; + bool first = true; + int err = 0; + + BUILD_BUG_ON(ARRAY_SIZE(names) >= BITS_PER_TYPE(mitigations)); + + str = kstrdup(val, GFP_KERNEL); + if (!str) + return -ENOMEM; + + for (sep = str; (tok = strsep(&sep, ","));) { + bool enable = true; + int i; + + /* Be tolerant of leading/trailing whitespace */ + tok = strim(tok); + + if (first) { + first = false; + + if (!strcmp(tok, "auto")) + continue; + + new = 0; + if (!strcmp(tok, "off")) + continue; + } + + if (*tok == '!') { + enable = !enable; + tok++; + } + + if (!strncmp(tok, "no", 2)) { + enable = !enable; + tok += 2; + } + + if (*tok == '\0') + continue; + + for (i = 0; i < ARRAY_SIZE(names); i++) { + if (!strcmp(tok, names[i])) { + if (enable) + new |= BIT(i); + else + new &= ~BIT(i); + break; + } + } + if (i == ARRAY_SIZE(names)) { + pr_err("Bad \"%s.mitigations=%s\", '%s' is unknown\n", + DRIVER_NAME, val, tok); + err = -EINVAL; + break; + } + } + kfree(str); + if (err) + return err; + + WRITE_ONCE(mitigations, new); + return 0; +} + +static int mitigations_get(char *buffer, const struct kernel_param *kp) +{ + unsigned long local = READ_ONCE(mitigations); + int count, i; + bool enable; + + if (!local) + return scnprintf(buffer, PAGE_SIZE, "%s\n", "off"); + + if (local & BIT(BITS_PER_LONG - 1)) { + count = scnprintf(buffer, PAGE_SIZE, "%s,", "auto"); + enable = false; + } else { + enable = true; + count = 0; + } + + for (i = 0; i < ARRAY_SIZE(names); i++) { + if ((local & BIT(i)) != enable) + continue; + + count += scnprintf(buffer + count, PAGE_SIZE - count, + "%s%s,", enable ? "" : "!", names[i]); + } + + buffer[count - 1] = '\n'; + return count; +} + +static const struct kernel_param_ops ops = { + .set = mitigations_set, + .get = mitigations_get, +}; + +module_param_cb_unsafe(mitigations, &ops, NULL, 0600); +MODULE_PARM_DESC(mitigations, +"Selectively enable security mitigations for all Intel® GPUs in the system.\n" +"\n" +" auto -- enables all mitigations required for the platform [default]\n" +" off -- disables all mitigations\n" +"\n" +"Individual mitigations can be enabled by passing a comma-separated string,\n" +"e.g. mitigations=residuals to enable only clearing residuals or\n" +"mitigations=auto,noresiduals to disable only the clear residual mitigation.\n" +"Either '!' or 'no' may be used to switch from enabling the mitigation to\n" +"disabling it.\n" +"\n" +"Active mitigations for Ivybridge, Baytrail, Haswell:\n" +" residuals -- clear all thread-local registers between contexts" +); --- /dev/null +++ b/drivers/gpu/drm/i915/i915_mitigations.h @@ -0,0 +1,13 @@ +/* SPDX-License-Identifier: MIT */ +/* + * Copyright © 2021 Intel Corporation + */ + +#ifndef __I915_MITIGATIONS_H__ +#define __I915_MITIGATIONS_H__ + +#include <linux/types.h> + +bool i915_mitigate_clear_residuals(void); + +#endif /* __I915_MITIGATIONS_H__ */
