[igt-dev] [PATCH i-g-t] igt/gem_ctx_isolation: Test INSTPM back to gen6

[Lionel Landwerlin]

On 29/05/18 12:16, Chris Wilson wrote:
> Lionel pointed out that INSTPM was context saved, at least from gen6,
> not from gen9. The only caveat is that INSTPM is a masked register (the
> upper 16bits are a write-enable mask, the lower 16bits the value to
> change) and also contains a read-only counter bit (which counts flushes,
> and so flip flops between batches). Being a non-privileged register that
> userspace wants to manipulate, it is writable and readable from a
> userspace batch, so we can test whether or not a write from one context
> is visible from a second.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

> ---
>   tests/gem_ctx_isolation.c | 51 ++++++++++++++++++++++++++++++++-------
>   1 file changed, 42 insertions(+), 9 deletions(-)
>
> diff --git a/tests/gem_ctx_isolation.c b/tests/gem_ctx_isolation.c
> index 4968e3678..fe7d3490c 100644
> --- a/tests/gem_ctx_isolation.c
> +++ b/tests/gem_ctx_isolation.c
> @@ -63,10 +63,12 @@ static const struct named_register {
>   	unsigned int engine_mask;
>   	uint32_t offset;
>   	uint32_t count;
> +	uint32_t ignore_bits;
> +	bool masked;
>   } nonpriv_registers[] = {
>   	{ "NOPID", NOCTX, RCS0, 0x2094 },
>   	{ "MI_PREDICATE_RESULT_2", NOCTX, RCS0, 0x23bc },
> -	{ "INSTPM", GEN9, RCS0, 0x20c0 },
> +	{ "INSTPM", GEN6, RCS0, 0x20c0, 1, BIT(8) /* ro counter */, true },
>   	{ "IA_VERTICES_COUNT", GEN4, RCS0, 0x2310, 2 },
>   	{ "IA_PRIMITIVES_COUNT", GEN4, RCS0, 0x2318, 2 },
>   	{ "VS_INVOCATION_COUNT", GEN4, RCS0, 0x2320, 2 },
> @@ -167,6 +169,17 @@ static const char *register_name(uint32_t offset, char *buf, size_t len)
>   	return "unknown";
>   }
>   
> +static const struct named_register *lookup_register(uint32_t offset)
> +{
> +	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)
> +			return r;
> +	}
> +
> +	return NULL;
> +}
> +
>   static bool ignore_register(uint32_t offset)
>   {
>   	for (const struct named_register *r = ignore_registers; r->name; r++) {
> @@ -283,7 +296,10 @@ static void write_regs(int fd,
>   		     count--; offset += 4) {
>   			*b++ = 0x22 << 23 | 1; /* LRI */
>   			*b++ = offset;
> -			*b++ = value;
> +			if (r->masked)
> +				*b++ = value | 0xffffu << 16;
> +			else
> +				*b++ = value;
>   		}
>   	}
>   	*b++ = MI_BATCH_BUFFER_END;
> @@ -424,14 +440,31 @@ static void compare_regs(int fd, uint32_t A, uint32_t B, const char *who)
>   
>   	num_errors = 0;
>   	for (unsigned int n = 0; n < NUM_REGS; n++) {
> +		const struct named_register *r;
>   		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++;
> -		}
> +		uint32_t mask;
> +
> +		if (a[n] == b[n])
> +			continue;
> +
> +		if (ignore_register(offset))
> +			continue;
> +
> +		mask = ~0u;
> +		r = lookup_register(offset);
> +		if (r && r->masked)
> +			mask >>= 16;
> +		if (r && r->ignore_bits)
> +			mask &= ~r->ignore_bits;
> +
> +		if ((a[n] & mask) == (b[n] & mask))
> +			continue;
> +
> +		igt_warn("Register 0x%04x (%s): A=%08x B=%08x\n",
> +			 offset,
> +			 register_name(offset, buf, sizeof(buf)),
> +			 a[n] & mask, b[n] & mask);
> +		num_errors++;
>   	}
>   	munmap(b, regs_size);
>   	munmap(a, regs_size);