[CI] igt/gem_ctx_isolation: Check isolation of registers between contexts

Submitted by Chris Wilson on Feb. 21, 2018, 8:26 a.m.

Details

Message ID 20180221082614.28555-1-chris@chris-wilson.co.uk
State New
Series "igt/gem_ctx_isolation: Check isolation of registers between contexts"
Headers show

Commit Message

Chris Wilson Feb. 21, 2018, 8:26 a.m.
A new context assumes that all of its registers are in the default state
when it is created. What may happen is that a register written by one
context may leak into the second, causing mass confusion.

v2: Extend back to Sandybridge (etc)
v3: Check context preserves registers across suspend/hibernate and resets.
v4: Complete the remapping onto the new class:instance
v5: Not like that, like this, try again to use class:instance
v6: Prepare for retrospective gen4 contexts!
v7: Repaint register set name to nonpriv, as this is what bspec calls the
registers that are writable by userspace.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
---
 tests/Makefile.sources    |   1 +
 tests/gem_ctx_isolation.c | 677 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/gem_exec_fence.c    |   2 +-
 3 files changed, 679 insertions(+), 1 deletion(-)
 create mode 100644 tests/gem_ctx_isolation.c

Patch hide | download patch | download mbox

diff --git a/tests/Makefile.sources b/tests/Makefile.sources
index 870c9093..b277de2f 100644
--- a/tests/Makefile.sources
+++ b/tests/Makefile.sources
@@ -57,6 +57,7 @@  TESTS_progs = \
 	gem_ctx_bad_exec \
 	gem_ctx_create \
 	gem_ctx_exec \
+	gem_ctx_isolation \
 	gem_ctx_param \
 	gem_ctx_switch \
 	gem_ctx_thrash \
diff --git a/tests/gem_ctx_isolation.c b/tests/gem_ctx_isolation.c
new file mode 100644
index 00000000..8b69cd33
--- /dev/null
+++ b/tests/gem_ctx_isolation.c
@@ -0,0 +1,677 @@ 
+/*
+ * Copyright © 2017 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "igt.h"
+#include "igt_dummyload.h"
+
+#define MAX_REG 0x40000
+#define NUM_REGS (MAX_REG / sizeof(uint32_t))
+
+#define PAGE_ALIGN(x) ALIGN(x, 4096)
+
+#define DIRTY1 0x1
+#define DIRTY2 0x2
+#define RESET 0x4
+
+#define BIT(x) (1ul << (x))
+#define ENGINE(x, y) BIT(4*(x) + (y))
+
+enum {
+	RCS0 = ENGINE(I915_ENGINE_CLASS_RENDER, 0),
+	BCS0 = ENGINE(I915_ENGINE_CLASS_COPY, 0),
+	VCS0 = ENGINE(I915_ENGINE_CLASS_VIDEO, 0),
+	VCS1 = ENGINE(I915_ENGINE_CLASS_VIDEO, 1),
+	VECS0 = ENGINE(I915_ENGINE_CLASS_VIDEO_ENHANCE, 0),
+};
+
+#define ALL ~0u
+#define GEN_RANGE(x, y) ((ALL >> (32 - (y - x + 1))) << x)
+#define GEN4 (ALL << 4)
+#define GEN5 (ALL << 5)
+#define GEN6 (ALL << 6)
+#define GEN7 (ALL << 7)
+#define GEN8 (ALL << 8)
+#define GEN9 (ALL << 9)
+
+#define NOCTX 0
+
+#define LAST_KNOWN_GEN 10
+
+static const struct named_register {
+	const char *name;
+	unsigned int gen_mask;
+	unsigned int engine_mask;
+	uint32_t offset;
+	uint32_t count;
+} nonpriv_registers[] = {
+	{ "NOPID", NOCTX, RCS0, 0x2094 },
+	{ "MI_PREDICATE_RESULT_2", NOCTX, RCS0, 0x23bc },
+	{ "INSTPM", GEN9, RCS0, 0x20c0 },
+	{ "IA_VERTICES_COUNT", GEN4, RCS0, 0x2310, 2 },
+	{ "IA_PRIMITIVES_COUNT", GEN4, RCS0, 0x2318, 2 },
+	{ "VS_INVOCATION_COUNT", GEN4, RCS0, 0x2320, 2 },
+	{ "HS_INVOCATION_COUNT", GEN4, RCS0, 0x2300, 2 },
+	{ "DS_INVOCATION_COUNT", GEN4, RCS0, 0x2308, 2 },
+	{ "GS_INVOCATION_COUNT", GEN4, RCS0, 0x2328, 2 },
+	{ "GS_PRIMITIVES_COUNT", GEN4, RCS0, 0x2330, 2 },
+	{ "CL_INVOCATION_COUNT", GEN4, RCS0, 0x2338, 2 },
+	{ "CL_PRIMITIVES_COUNT", GEN4, RCS0, 0x2340, 2 },
+	{ "PS_INVOCATION_COUNT_0", GEN4, RCS0, 0x22c8, 2 },
+	{ "PS_DEPTH_COUNT_0", GEN4, RCS0, 0x22d8, 2 },
+	{ "GPUGPU_DISPATCHDIMX", GEN8, RCS0, 0x2500 },
+	{ "GPUGPU_DISPATCHDIMY", GEN8, RCS0, 0x2504 },
+	{ "GPUGPU_DISPATCHDIMZ", GEN8, RCS0, 0x2508 },
+	{ "MI_PREDICATE_SRC0", GEN8, RCS0, 0x2400, 2 },
+	{ "MI_PREDICATE_SRC1", GEN8, RCS0, 0x2408, 2 },
+	{ "MI_PREDICATE_DATA", GEN8, RCS0, 0x2410, 2 },
+	{ "MI_PRED_RESULT", GEN8, RCS0, 0x2418 },
+	{ "3DPRIM_END_OFFSET", GEN6, RCS0, 0x2420 },
+	{ "3DPRIM_START_VERTEX", GEN6, RCS0, 0x2430 },
+	{ "3DPRIM_VERTEX_COUNT", GEN6, RCS0, 0x2434 },
+	{ "3DPRIM_INSTANCE_COUNT", GEN6, RCS0, 0x2438 },
+	{ "3DPRIM_START_INSTANCE", GEN6, RCS0, 0x243c },
+	{ "3DPRIM_BASE_VERTEX", GEN6, RCS0, 0x2440 },
+	{ "GPGPU_THREADS_DISPATCHED", GEN8, RCS0, 0x2290, 2 },
+	{ "PS_INVOCATION_COUNT_1", GEN8, RCS0, 0x22f0, 2 },
+	{ "PS_DEPTH_COUNT_1", GEN8, RCS0, 0x22f8, 2 },
+	{ "BB_OFFSET", GEN8, RCS0, 0x2158 },
+	{ "MI_PREDICATE_RESULT_1", GEN8, RCS0, 0x241c },
+	{ "CS_GPR", GEN8, RCS0, 0x2600, 32 },
+	{ "OA_CTX_CONTROL", GEN8, RCS0, 0x2360 },
+	{ "OACTXID", GEN8, RCS0, 0x2364 },
+	{ "PS_INVOCATION_COUNT_2", GEN8, RCS0, 0x2448, 2 },
+	{ "PS_DEPTH_COUNT_2", GEN8, RCS0, 0x2450, 2 },
+	{ "Cache_Mode_0", GEN7, RCS0, 0x7000 },
+	{ "Cache_Mode_1", GEN7, RCS0, 0x7004 },
+	{ "GT_MODE", GEN8, RCS0, 0x7008 },
+	{ "L3_Config", GEN7, RCS0, 0x7034 },
+	{ "TD_CTL", GEN8, RCS0, 0xe400 },
+	{ "TD_CTL2", GEN8, RCS0, 0xe404 },
+	{ "SO_NUM_PRIMS_WRITEN0", GEN6, RCS0, 0x5200, 2 },
+	{ "SO_NUM_PRIMS_WRITEN1", GEN6, RCS0, 0x5208, 2 },
+	{ "SO_NUM_PRIMS_WRITEN2", GEN6, RCS0, 0x5210, 2 },
+	{ "SO_NUM_PRIMS_WRITEN3", GEN6, RCS0, 0x5218, 2 },
+	{ "SO_PRIM_STORAGE_NEEDED0", GEN6, RCS0, 0x5240, 2 },
+	{ "SO_PRIM_STORAGE_NEEDED1", GEN6, RCS0, 0x5248, 2 },
+	{ "SO_PRIM_STORAGE_NEEDED2", GEN6, RCS0, 0x5250, 2 },
+	{ "SO_PRIM_STORAGE_NEEDED3", GEN6, RCS0, 0x5258, 2 },
+	{ "SO_WRITE_OFFSET0", GEN7, RCS0, 0x5280 },
+	{ "SO_WRITE_OFFSET1", GEN7, RCS0, 0x5284 },
+	{ "SO_WRITE_OFFSET2", GEN7, RCS0, 0x5288 },
+	{ "SO_WRITE_OFFSET3", GEN7, RCS0, 0x528c },
+	{ "OA_CONTROL", NOCTX, RCS0, 0x2b00 },
+	{ "PERF_CNT_1", NOCTX, RCS0, 0x91b8, 2 },
+	{ "PERF_CNT_2", NOCTX, RCS0, 0x91c0, 2 },
+
+	/* Privileged (enabled by w/a + FORCE_TO_NONPRIV) */
+	{ "CTX_PREEMPT", NOCTX /* GEN_RANGE(9, 10) */, RCS0, 0x2248 },
+	{ "CS_CHICKEN1", GEN_RANGE(9, 10), RCS0, 0x2580 },
+	{ "HDC_CHICKEN1", GEN_RANGE(9, 10), RCS0, 0x7304 },
+	{ "L3SQREG1", GEN8, RCS0, 0xb010 },
+
+	{ "BCS_GPR", GEN9, BCS0, 0x22600, 32 },
+	{ "BCS_SWCTRL", GEN8, BCS0, 0x22200 },
+
+	{ "VCS0_GPR", GEN9, VCS0, 0x12600, 32 },
+	{ "MFC_VDBOX1", NOCTX, VCS0, 0x12800, 64 },
+
+	{ "VCS1_GPR", GEN9, VCS1, 0x1c600, 32 },
+	{ "MFC_VDBOX2", NOCTX, VCS1, 0x1c800, 64 },
+
+	{ "VECS_GPR", GEN9, VECS0, 0x1a600, 32 },
+
+	{}
+}, ignore_registers[] = {
+	{ "RCS timestamp", GEN6, ~0u, 0x2358 },
+	{ "VCS0 timestamp", GEN7, ~0u, 0x12358 },
+	{ "VCS1 timestamp", GEN7, ~0u, 0x1c358 },
+	{ "BCS timestamp", GEN7, ~0u, 0x22358 },
+	{ "VECS timestamp", GEN8, ~0u, 0x1a358 },
+	{}
+};
+
+static const char *register_name(uint32_t offset, char *buf, size_t len)
+{
+	for (const struct named_register *r = nonpriv_registers; r->name; r++) {
+		unsigned int width = r->count ? 4*r->count : 4;
+		if (offset >= r->offset && offset < r->offset + width) {
+			if (r->count <= 1)
+				return r->name;
+
+			snprintf(buf, len, "%s[%d]",
+				 r->name, (offset - r->offset)/4);
+			return buf;
+		}
+	}
+
+	return "unknown";
+}
+
+static bool ignore_register(uint32_t offset)
+{
+	for (const struct named_register *r = ignore_registers; r->name; r++) {
+		unsigned int width = r->count ? 4*r->count : 4;
+		if (offset >= r->offset && offset < r->offset + width)
+			return true;
+	}
+
+	return false;
+}
+
+static uint32_t read_regs(int fd,
+			  uint32_t ctx,
+			  const struct intel_execution_engine2 *e,
+			  unsigned int flags)
+{
+	const unsigned int gen = intel_gen(intel_get_drm_devid(fd));
+	const unsigned int gen_bit = 1 << gen;
+	const unsigned int engine_bit = ENGINE(e->class, e->instance);
+	const bool r64b = gen >= 8;
+	struct drm_i915_gem_exec_object2 obj[2];
+	struct drm_i915_gem_relocation_entry *reloc;
+	struct drm_i915_gem_execbuffer2 execbuf;
+	unsigned int regs_size, batch_size, n;
+	uint32_t *batch, *b;
+
+	reloc = calloc(NUM_REGS, sizeof(*reloc));
+	igt_assert(reloc);
+
+	regs_size = NUM_REGS * sizeof(uint32_t);
+	regs_size = PAGE_ALIGN(regs_size);
+
+	batch_size = NUM_REGS * 4 * sizeof(uint32_t) + 4;
+	batch_size = PAGE_ALIGN(batch_size);
+
+	memset(obj, 0, sizeof(obj));
+	obj[0].handle = gem_create(fd, regs_size);
+	obj[1].handle = gem_create(fd, batch_size);
+	obj[1].relocs_ptr = to_user_pointer(reloc);
+
+	b = batch = gem_mmap__cpu(fd, obj[1].handle, 0, batch_size, PROT_WRITE);
+	gem_set_domain(fd, obj[1].handle,
+		       I915_GEM_DOMAIN_CPU, I915_GEM_DOMAIN_CPU);
+
+	n = 0;
+	for (const struct named_register *r = nonpriv_registers; r->name; r++) {
+		if (!(r->engine_mask & engine_bit))
+			continue;
+		if (!(r->gen_mask & gen_bit))
+			continue;
+
+		for (unsigned count = r->count ?: 1, offset = r->offset;
+		     count--; offset += 4) {
+			*b++ = 0x24 << 23 | (1 + r64b); /* SRM */
+			*b++ = offset;
+			reloc[n].target_handle = obj[0].handle;
+			reloc[n].presumed_offset = 0;
+			reloc[n].offset = (b - batch) * sizeof(*b);
+			reloc[n].delta = offset;
+			reloc[n].read_domains = I915_GEM_DOMAIN_RENDER;
+			reloc[n].write_domain = I915_GEM_DOMAIN_RENDER;
+			*b++ = offset;
+			if (r64b)
+				*b++ = 0;
+			n++;
+		}
+	}
+
+	obj[1].relocation_count = n;
+	*b++ = MI_BATCH_BUFFER_END;
+	munmap(batch, batch_size);
+
+	memset(&execbuf, 0, sizeof(execbuf));
+	execbuf.buffers_ptr = to_user_pointer(obj);
+	execbuf.buffer_count = 2;
+	execbuf.flags =
+		gem_class_instance_to_eb_flags(fd, e->class, e->instance);
+	execbuf.rsvd1 = ctx;
+	gem_execbuf(fd, &execbuf);
+	gem_close(fd, obj[1].handle);
+	free(reloc);
+
+	return obj[0].handle;
+}
+
+static void write_regs(int fd,
+		       uint32_t ctx,
+		       const struct intel_execution_engine2 *e,
+		       unsigned int flags,
+		       uint32_t value)
+{
+	const unsigned int gen_bit = 1 << intel_gen(intel_get_drm_devid(fd));
+	const unsigned int engine_bit = ENGINE(e->class, e->instance);
+	struct drm_i915_gem_exec_object2 obj;
+	struct drm_i915_gem_execbuffer2 execbuf;
+	unsigned int batch_size;
+	uint32_t *batch, *b;
+
+	batch_size = NUM_REGS * 3 * sizeof(uint32_t) + 4;
+	batch_size = PAGE_ALIGN(batch_size);
+
+	memset(&obj, 0, sizeof(obj));
+	obj.handle = gem_create(fd, batch_size);
+
+	b = batch = gem_mmap__cpu(fd, obj.handle, 0, batch_size, PROT_WRITE);
+	gem_set_domain(fd, obj.handle,
+		       I915_GEM_DOMAIN_CPU, I915_GEM_DOMAIN_CPU);
+	for (const struct named_register *r = nonpriv_registers; r->name; r++) {
+		if (!(r->engine_mask & engine_bit))
+			continue;
+		if (!(r->gen_mask & gen_bit))
+			continue;
+		for (unsigned count = r->count ?: 1, offset = r->offset;
+		     count--; offset += 4) {
+			*b++ = 0x22 << 23 | 1; /* LRI */
+			*b++ = offset;
+			*b++ = value;
+		}
+	}
+	*b++ = MI_BATCH_BUFFER_END;
+	munmap(batch, batch_size);
+
+	memset(&execbuf, 0, sizeof(execbuf));
+	execbuf.buffers_ptr = to_user_pointer(&obj);
+	execbuf.buffer_count = 1;
+	execbuf.flags =
+		gem_class_instance_to_eb_flags(fd, e->class, e->instance);
+	execbuf.rsvd1 = ctx;
+	gem_execbuf(fd, &execbuf);
+	gem_close(fd, obj.handle);
+}
+
+static void restore_regs(int fd,
+			 uint32_t ctx,
+			 const struct intel_execution_engine2 *e,
+			 unsigned int flags,
+			 uint32_t regs)
+{
+	const unsigned int gen = intel_gen(intel_get_drm_devid(fd));
+	const unsigned int gen_bit = 1 << gen;
+	const unsigned int engine_bit = ENGINE(e->class, e->instance);
+	const bool r64b = gen >= 8;
+	struct drm_i915_gem_exec_object2 obj[2];
+	struct drm_i915_gem_execbuffer2 execbuf;
+	struct drm_i915_gem_relocation_entry *reloc;
+	unsigned int batch_size, n;
+	uint32_t *batch, *b;
+
+	if (gen < 7) /* no LRM */
+		return;
+
+	reloc = calloc(NUM_REGS, sizeof(*reloc));
+	igt_assert(reloc);
+
+	batch_size = NUM_REGS * 3 * sizeof(uint32_t) + 4;
+	batch_size = PAGE_ALIGN(batch_size);
+
+	memset(obj, 0, sizeof(obj));
+	obj[0].handle = regs;
+	obj[1].handle = gem_create(fd, batch_size);
+	obj[1].relocs_ptr = to_user_pointer(reloc);
+
+	b = batch = gem_mmap__cpu(fd, obj[1].handle, 0, batch_size, PROT_WRITE);
+	gem_set_domain(fd, obj[1].handle,
+		       I915_GEM_DOMAIN_CPU, I915_GEM_DOMAIN_CPU);
+
+	n = 0;
+	for (const struct named_register *r = nonpriv_registers; r->name; r++) {
+		if (!(r->engine_mask & engine_bit))
+			continue;
+		if (!(r->gen_mask & gen_bit))
+			continue;
+
+		for (unsigned count = r->count ?: 1, offset = r->offset;
+		     count--; offset += 4) {
+			*b++ = 0x29 << 23 | (1 + r64b); /* LRM */
+			*b++ = offset;
+			reloc[n].target_handle = obj[0].handle;
+			reloc[n].presumed_offset = 0;
+			reloc[n].offset = (b - batch) * sizeof(*b);
+			reloc[n].delta = offset;
+			reloc[n].read_domains = I915_GEM_DOMAIN_RENDER;
+			reloc[n].write_domain = 0;
+			*b++ = offset;
+			if (gen >= 9)
+				*b++ = 0;
+			n++;
+		}
+	}
+	obj[1].relocation_count = n;
+	*b++ = MI_BATCH_BUFFER_END;
+	munmap(batch, batch_size);
+
+	memset(&execbuf, 0, sizeof(execbuf));
+	execbuf.buffers_ptr = to_user_pointer(obj);
+	execbuf.buffer_count = 2;
+	execbuf.flags =
+		gem_class_instance_to_eb_flags(fd, e->class, e->instance);
+	execbuf.rsvd1 = ctx;
+	gem_execbuf(fd, &execbuf);
+	gem_close(fd, obj[1].handle);
+}
+
+__attribute__((unused))
+static void dump_regs(int fd,
+		      const struct intel_execution_engine2 *e,
+		      unsigned int regs)
+{
+	const int gen = intel_gen(intel_get_drm_devid(fd));
+	const unsigned int gen_bit = 1 << gen;
+	const unsigned int engine_bit = ENGINE(e->class, e->instance);
+	unsigned int regs_size;
+	uint32_t *out;
+
+	regs_size = NUM_REGS * sizeof(uint32_t);
+	regs_size = PAGE_ALIGN(regs_size);
+
+	out = gem_mmap__cpu(fd, regs, 0, regs_size, PROT_READ);
+	gem_set_domain(fd, regs, I915_GEM_DOMAIN_CPU, 0);
+
+	for (const struct named_register *r = nonpriv_registers; r->name; r++) {
+		if (!(r->engine_mask & engine_bit))
+			continue;
+		if (!(r->gen_mask & gen_bit))
+			continue;
+
+		if (r->count <= 1) {
+			igt_debug("0x%04x (%s): 0x%08x\n",
+				  r->offset, r->name, out[r->offset/4]);
+		} else {
+			for (unsigned x = 0; x < r->count; x++)
+				igt_debug("0x%04x (%s[%d]): 0x%08x\n",
+					  r->offset+4*x, r->name, x,
+					  out[r->offset/4 + x]);
+		}
+	}
+	munmap(out, regs_size);
+}
+
+static void compare_regs(int fd, uint32_t A, uint32_t B, const char *who)
+{
+	unsigned int num_errors;
+	unsigned int regs_size;
+	uint32_t *a, *b;
+	char buf[80];
+
+	regs_size = NUM_REGS * sizeof(uint32_t);
+	regs_size = PAGE_ALIGN(regs_size);
+
+	a = gem_mmap__cpu(fd, A, 0, regs_size, PROT_READ);
+	gem_set_domain(fd, A, I915_GEM_DOMAIN_CPU, 0);
+
+	b = gem_mmap__cpu(fd, B, 0, regs_size, PROT_READ);
+	gem_set_domain(fd, B, I915_GEM_DOMAIN_CPU, 0);
+
+	num_errors = 0;
+	for (unsigned int n = 0; n < NUM_REGS; n++) {
+		uint32_t offset = n * sizeof(uint32_t);
+		if (a[n] != b[n] && !ignore_register(offset)) {
+			igt_warn("Register 0x%04x (%s): A=%08x B=%08x\n",
+				 offset,
+				 register_name(offset, buf, sizeof(buf)),
+				 a[n], b[n]);
+			num_errors++;
+		}
+	}
+	munmap(b, regs_size);
+	munmap(a, regs_size);
+
+	igt_assert_f(num_errors == 0,
+		     "%d registers mistached between %s.\n",
+		     num_errors, who);
+}
+
+static void isolation(int fd,
+		      const struct intel_execution_engine2 *e,
+		      unsigned int flags)
+{
+	static const uint32_t values[] = {
+		0x0,
+		0xffffffff,
+		0xcccccccc,
+		0x33333333,
+		0x55555555,
+		0xaaaaaaaa,
+		0xdeadbeef
+	};
+	unsigned int engine = gem_class_instance_to_eb_flags(fd,
+							     e->class,
+							     e->instance);
+	unsigned int num_values =
+		flags & (DIRTY1 | DIRTY2) ? ARRAY_SIZE(values) : 1;
+
+	gem_quiescent_gpu(fd);
+
+	for (int v = 0; v < num_values; v++) {
+		igt_spin_t *spin = NULL;
+		uint32_t ctx[2], regs[2], tmp;
+
+		ctx[0] = gem_context_create(fd);
+		regs[0] = read_regs(fd, ctx[0], e, flags);
+
+		spin = igt_spin_batch_new(fd, ctx[0], engine, 0);
+
+		if (flags & DIRTY1) {
+			igt_debug("%s[%d]: Setting all registers of ctx 0 to 0x%08x\n",
+				  __func__, v, values[v]);
+			write_regs(fd, ctx[0], e, flags, values[v]);
+		}
+
+		/*
+		 * We create and execute a new context, whilst the HW is
+		 * occupied with the previous context (we should switch from
+		 * the old to the new proto-context without idling, which could
+		 * then load the powercontext). If all goes well, we only see
+		 * the default values from this context, but if goes badly we
+		 * see the corruption from the previous context instead!
+		 */
+		ctx[1] = gem_context_create(fd);
+		regs[1] = read_regs(fd, ctx[1], e, flags);
+
+		if (flags & DIRTY2) {
+			igt_debug("%s[%d]: Setting all registers of ctx 1 to 0x%08x\n",
+				  __func__, v, ~values[v]);
+			write_regs(fd, ctx[1], e, flags, ~values[v]);
+		}
+
+		/*
+		 * Restore the original register values before the HW idles.
+		 * Or else it may never restart!
+		 */
+		tmp = read_regs(fd, ctx[0], e, flags);
+		restore_regs(fd, ctx[0], e, flags, regs[0]);
+
+		igt_spin_batch_free(fd, spin);
+
+		if (!(flags & DIRTY1))
+			compare_regs(fd, regs[0], tmp, "two reads of the same ctx");
+		compare_regs(fd, regs[0], regs[1], "two virgin contexts");
+
+		for (int n = 0; n < ARRAY_SIZE(ctx); n++) {
+			gem_close(fd, regs[n]);
+			gem_context_destroy(fd, ctx[n]);
+		}
+		gem_close(fd, tmp);
+	}
+}
+
+#define NOSLEEP (0 << 8)
+#define S3_DEVICES (1 << 8)
+#define S3 (2 << 8)
+#define S4_DEVICES (3 << 8)
+#define S4 (4 << 8)
+#define SLEEP_MASK (0xf << 8)
+
+static void preservation(int fd,
+			 const struct intel_execution_engine2 *e,
+			 unsigned int flags)
+{
+	static const uint32_t values[] = {
+		0x0,
+		0xffffffff,
+		0xcccccccc,
+		0x33333333,
+		0x55555555,
+		0xaaaaaaaa,
+		0xdeadbeef
+	};
+	const unsigned int num_values = ARRAY_SIZE(values);
+	unsigned int engine =
+		gem_class_instance_to_eb_flags(fd, e->class, e->instance);
+	uint32_t ctx[num_values +1 ];
+	uint32_t regs[num_values + 1][2];
+	igt_spin_t *spin;
+
+	gem_quiescent_gpu(fd);
+
+	ctx[num_values] = gem_context_create(fd);
+	spin = igt_spin_batch_new(fd, ctx[num_values], engine, 0);
+	regs[num_values][0] = read_regs(fd, ctx[num_values], e, flags);
+	for (int v = 0; v < num_values; v++) {
+		ctx[v] = gem_context_create(fd);
+		write_regs(fd, ctx[v], e, flags, values[v]);
+
+		regs[v][0] = read_regs(fd, ctx[v], e, flags);
+
+	}
+	gem_close(fd, read_regs(fd, ctx[num_values], e, flags));
+	igt_spin_batch_free(fd, spin);
+
+	if (flags & RESET)
+		igt_force_gpu_reset(fd);
+
+	switch (flags & SLEEP_MASK) {
+	case NOSLEEP:
+		break;
+
+	case S3_DEVICES:
+		igt_system_suspend_autoresume(SUSPEND_STATE_MEM,
+					      SUSPEND_TEST_DEVICES);
+		break;
+
+	case S3:
+		igt_system_suspend_autoresume(SUSPEND_STATE_MEM,
+					      SUSPEND_TEST_NONE);
+		break;
+
+	case S4_DEVICES:
+		igt_system_suspend_autoresume(SUSPEND_STATE_DISK,
+					      SUSPEND_TEST_DEVICES);
+		break;
+
+	case S4:
+		igt_system_suspend_autoresume(SUSPEND_STATE_DISK,
+					      SUSPEND_TEST_NONE);
+		break;
+	}
+
+	spin = igt_spin_batch_new(fd, ctx[num_values], engine, 0);
+	for (int v = 0; v < num_values; v++)
+		regs[v][1] = read_regs(fd, ctx[v], e, flags);
+	regs[num_values][1] = read_regs(fd, ctx[num_values], e, flags);
+	igt_spin_batch_free(fd, spin);
+
+	for (int v = 0; v < num_values; v++) {
+		char buf[80];
+
+		snprintf(buf, sizeof(buf), "dirty %x context\n", values[v]);
+		compare_regs(fd, regs[v][0], regs[v][1], buf);
+
+		gem_close(fd, regs[v][0]);
+		gem_close(fd, regs[v][1]);
+		gem_context_destroy(fd, ctx[v]);
+	}
+	compare_regs(fd, regs[num_values][0], regs[num_values][1], "clean");
+	gem_context_destroy(fd, ctx[num_values]);
+}
+
+static unsigned int __has_context_isolation(int fd)
+{
+	struct drm_i915_getparam gp;
+	int value = 0;
+
+	memset(&gp, 0, sizeof(gp));
+	gp.param = 50; /* I915_PARAM_HAS_CONTEXT_ISOLATION */
+	gp.value = &value;
+
+	igt_ioctl(fd, DRM_IOCTL_I915_GETPARAM, &gp);
+	errno = 0;
+
+	return value;
+}
+
+igt_main
+{
+	unsigned int has_context_isolation = 0;
+	int fd = -1;
+
+	igt_fixture {
+		int gen;
+
+		fd = drm_open_driver(DRIVER_INTEL);
+		igt_require_gem(fd);
+
+		gem_context_destroy(fd, gem_context_create(fd));
+		has_context_isolation = __has_context_isolation(fd);
+		igt_require(has_context_isolation);
+
+		gen = intel_gen(intel_get_drm_devid(fd));
+		//igt_ci_fail_on(gen > LAST_KNOWN_GEN);
+		igt_skip_on(gen > LAST_KNOWN_GEN);
+	}
+
+	for (const struct intel_execution_engine2 *e = intel_execution_engines2;
+	     e->name; e++) {
+		igt_subtest_group {
+			igt_fixture {
+				igt_require(has_context_isolation & (1 << e->class));
+				gem_require_engine(fd, e->class, e->instance);
+				igt_fork_hang_detector(fd);
+			}
+
+			igt_subtest_f("%s-clean", e->name)
+				isolation(fd, e, 0);
+			igt_subtest_f("%s-dirty-create", e->name)
+				isolation(fd, e, DIRTY1);
+			igt_subtest_f("%s-dirty-switch", e->name)
+				isolation(fd, e, DIRTY2);
+
+			igt_subtest_f("%s-none", e->name)
+				preservation(fd, e, 0);
+			igt_subtest_f("%s-S3", e->name)
+				preservation(fd, e, S3);
+			igt_subtest_f("%s-S4", e->name)
+				preservation(fd, e, S4);
+
+			igt_fixture {
+				igt_stop_hang_detector();
+			}
+
+			igt_subtest_f("%s-reset", e->name) {
+				igt_hang_t hang = igt_allow_hang(fd, 0, 0);
+				preservation(fd, e, RESET);
+				igt_disallow_hang(fd, hang);
+			}
+		}
+	}
+}
diff --git a/tests/gem_exec_fence.c b/tests/gem_exec_fence.c
index 8dd758aa..312505d6 100644
--- a/tests/gem_exec_fence.c
+++ b/tests/gem_exec_fence.c
@@ -793,7 +793,7 @@  static bool has_submit_fence(int fd)
 	int value = 0;
 
 	memset(&gp, 0, sizeof(gp));
-	gp.param = 50; /* I915_PARAM_HAS_EXEC_SUBMIT_FENCE */
+	gp.param = 0xdeadbeef ^ 51; /* I915_PARAM_HAS_EXEC_SUBMIT_FENCE */
 	gp.value = &value;
 
 	ioctl(fd, DRM_IOCTL_I915_GETPARAM, &gp, sizeof(gp));