Re: [igt-dev] [i-g-t] lib/ioctl_wrappers: Keep IGT working without pread/pwrite ioctls

[Jason Ekstrand <jason@jlekstrand.net>]

Sorry for breaking the reply thread but I just subscribed to the I-G-T
mailing list today.  Shouldn't be a problem going forward.

Ashutosh Dixit <ashutosh.dixit@intel.com> wrote:
> The general direction at this time is to phase out pread/write ioctls
> and not support them in future products. This means IGT must handle
> the absence of these ioctls. This patch does this by modifying
> gem_read() and gem_write() to do the read/write using the pread/pwrite
> ioctls first but when these ioctls are unavailable fall back to doing
> the read/write using a combination of mmap and memcpy.
>
> Callers who must absolutely use the pread/pwrite ioctls (such as tests
> which test these ioctls or must otherwise only use the pread/pwrite
> ioctls) must use gem_require_pread_pwrite() to skip when these ioctls
> are not available.
>
> v1: Removed __gem_pread, gem_pread, __gem_pwrite and gem_pwrite
>     introduced previously since they are not necessary,
>     gem_require_pread_pwrite is sufficient
> v2: Fix CI failures in gem_advise and gen9_exec_parse by introducing
>     gem_require_pread_pwrite
> v3: Skip mmap for 0 length read/write's
> v4: Remove redundant igt_assert's
> v5: Re-run
> v6: s/EOPNOTSUPP/-EOPNOTSUPP/
> v7: Rebase on latest master, skip gem_exec_parallel@userptr with
>     gem_require_pread_pwrite
>
> Reviewed-by: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com>
> Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
> ---
>  lib/ioctl_wrappers.c                        | 135 +++++++++++++++++++-
>  lib/ioctl_wrappers.h                        |   3 +
>  tests/i915/gem_exec_parallel.c              |   3 +
>  tests/i915/gem_madvise.c                    |   2 +
>  tests/i915/gem_partial_pwrite_pread.c       |   1 +
>  tests/i915/gem_pread.c                      |   1 +
>  tests/i915/gem_pread_after_blit.c           |   1 +
>  tests/i915/gem_pwrite.c                     |   1 +
>  tests/i915/gem_pwrite_snooped.c             |   1 +
>  tests/i915/gem_readwrite.c                  |   1 +
>  tests/i915/gem_set_tiling_vs_pwrite.c       |   1 +
>  tests/i915/gem_tiled_partial_pwrite_pread.c |   1 +
>  tests/i915/gem_tiled_pread_basic.c          |   1 +
>  tests/i915/gem_tiled_pread_pwrite.c         |   1 +
>  tests/i915/gem_userptr_blits.c              |   2 +
>  tests/i915/gen9_exec_parse.c                |   4 +-
>  16 files changed, 152 insertions(+), 7 deletions(-)
>
> diff --git a/lib/ioctl_wrappers.c b/lib/ioctl_wrappers.c
> index 45415621b7..4440004c42 100644
> --- a/lib/ioctl_wrappers.c
> +++ b/lib/ioctl_wrappers.c
> @@ -56,6 +56,7 @@
>  #include "igt_debugfs.h"
>  #include "igt_sysfs.h"
>  #include "config.h"
> +#include "i915/gem_mman.h"
>
>  #ifdef HAVE_VALGRIND
>  #include <valgrind/valgrind.h>
> @@ -324,6 +325,70 @@ void gem_close(int fd, uint32_t handle)
>      do_ioctl(fd, DRM_IOCTL_GEM_CLOSE, &close_bo);
>  }
>
> +static bool is_cache_coherent(int fd, uint32_t handle)
> +{
> +    return gem_get_caching(fd, handle) != I915_CACHING_NONE;
> +}
> +
> +static void mmap_write(int fd, uint32_t handle, uint64_t offset,
> +               const void *buf, uint64_t length)
> +{
> +    void *map = NULL;
> +
> +    if (!length)
> +        return;
> +
> +    if (is_cache_coherent(fd, handle)) {
> +        /* offset arg for mmap functions must be 0 */
> +        map = __gem_mmap__cpu_coherent(fd, handle, 0, offset + length,
> +                           PROT_READ | PROT_WRITE);
> +        if (map)
> +            gem_set_domain(fd, handle,
> +                       I915_GEM_DOMAIN_CPU, I915_GEM_DOMAIN_CPU);

Not sure how much it matters for IGT but the pread/pwrite ioctls
appear to always leave the BO in the GTT domain.

Otherwise, everything here looks pretty sane.

--Jason

> +    }
> +
> +    if (!map) {
> +        map = __gem_mmap_offset__wc(fd, handle, 0, offset + length,
> +                        PROT_READ | PROT_WRITE);
> +        if (!map)
> +            map = gem_mmap__wc(fd, handle, 0, offset + length,
> +                       PROT_READ | PROT_WRITE);
> +        gem_set_domain(fd, handle,
> +                   I915_GEM_DOMAIN_WC, I915_GEM_DOMAIN_WC);
> +    }
> +
> +    memcpy(map + offset, buf, length);
> +    munmap(map, offset + length);
> +}
> +
> +static void mmap_read(int fd, uint32_t handle, uint64_t offset, void *buf, uint64_t length)
> +{
> +    void *map = NULL;
> +
> +    if (!length)
> +        return;
> +
> +    if (gem_has_llc(fd) || is_cache_coherent(fd, handle)) {
> +        /* offset arg for mmap functions must be 0 */
> +        map = __gem_mmap__cpu_coherent(fd, handle, 0,
> +                           offset + length, PROT_READ);
> +        if (map)
> +            gem_set_domain(fd, handle, I915_GEM_DOMAIN_CPU, 0);
> +    }
> +
> +    if (!map) {
> +        map = __gem_mmap_offset__wc(fd, handle, 0, offset + length,
> +                        PROT_READ);
> +        if (!map)
> +            map = gem_mmap__wc(fd, handle, 0, offset + length,
> +                       PROT_READ);
> +        gem_set_domain(fd, handle, I915_GEM_DOMAIN_WC, 0);
> +    }
> +
> +    memcpy(buf, map + offset, length);
> +    munmap(map, offset + length);
> +}
> +
>  int __gem_write(int fd, uint32_t handle, uint64_t offset, const void *buf, uint64_t length)
>  {
>      struct drm_i915_gem_pwrite gem_pwrite;
> @@ -349,12 +414,18 @@ int __gem_write(int fd, uint32_t handle, uint64_t offset, const void *buf, uint6
>   * @buf: pointer to the data to write into the buffer
>   * @length: size of the subrange
>   *
> - * This wraps the PWRITE ioctl, which is to upload a linear data to a subrange
> - * of a gem buffer object.
> + * Method to write to a gem object. Uses the PWRITE ioctl when it is
> + * available, else it uses mmap + memcpy to upload linear data to a
> + * subrange of a gem buffer object.
>   */
>  void gem_write(int fd, uint32_t handle, uint64_t offset, const void *buf, uint64_t length)
>  {
> -    igt_assert_eq(__gem_write(fd, handle, offset, buf, length), 0);
> +    int ret = __gem_write(fd, handle, offset, buf, length);
> +
> +    igt_assert(ret == 0 || ret == -EOPNOTSUPP);
> +
> +    if (ret == -EOPNOTSUPP)
> +        mmap_write(fd, handle, offset, buf, length);
>  }
>
>  int __gem_read(int fd, uint32_t handle, uint64_t offset, void *buf, uint64_t length)
> @@ -381,12 +452,64 @@ int __gem_read(int fd, uint32_t handle, uint64_t offset, void *buf, uint64_t len
>   * @buf: pointer to the data to read into
>   * @length: size of the subrange
>   *
> - * This wraps the PREAD ioctl, which is to download a linear data to a subrange
> - * of a gem buffer object.
> + * Method to read from a gem object. Uses the PREAD ioctl when it is
> + * available, else it uses mmap + memcpy to download linear data from a
> + * subrange of a gem buffer object.
>   */
>  void gem_read(int fd, uint32_t handle, uint64_t offset, void *buf, uint64_t length)
>  {
> -    igt_assert_eq(__gem_read(fd, handle, offset, buf, length), 0);
> +    int ret = __gem_read(fd, handle, offset, buf, length);
> +
> +    igt_assert(ret == 0 || ret == -EOPNOTSUPP);
> +
> +    if (ret == -EOPNOTSUPP)
> +        mmap_read(fd, handle, offset, buf, length);
> +}
> +
> +/**
> + * gem_has_pwrite
> + * @fd: open i915 drm file descriptor
> + *
> + * Feature test macro to query whether pwrite ioctl is supported
> + */
> +bool gem_has_pwrite(int fd)
> +{
> +    uint32_t handle = gem_create(fd, 4096);
> +    int buf, ret;
> +
> +    ret = __gem_write(fd, handle, 0, &buf, sizeof(buf));
> +    gem_close(fd, handle);
> +
> +    return ret != -EOPNOTSUPP;
> +}
> +
> +/**
> + * gem_has_pread
> + * @fd: open i915 drm file descriptor
> + *
> + * Feature test macro to query whether pread ioctl is supported
> + */
> +bool gem_has_pread(int fd)
> +{
> +    uint32_t handle = gem_create(fd, 4096);
> +    int buf, ret;
> +
> +    ret = __gem_read(fd, handle, 0, &buf, sizeof(buf));
> +    gem_close(fd, handle);
> +
> +    return ret != -EOPNOTSUPP;
> +}
> +
> +/**
> + * gem_require_pread_pwrite
> + * @fd: open i915 drm file descriptor
> + *
> + * Feature test macro to query whether pread/pwrite ioctls are supported
> + * and skip if they are not
> + */
> +void gem_require_pread_pwrite(int fd)
> +{
> +    igt_require(gem_has_pread(fd) && gem_has_pwrite(fd));
>  }
>
>  int __gem_set_domain(int fd, uint32_t handle, uint32_t read, uint32_t write)
> diff --git a/lib/ioctl_wrappers.h b/lib/ioctl_wrappers.h
> index 69e198419c..9ea673653e 100644
> --- a/lib/ioctl_wrappers.h
> +++ b/lib/ioctl_wrappers.h
> @@ -71,6 +71,9 @@ int __gem_write(int fd, uint32_t handle, uint64_t offset, const void *buf, uint6
>  void gem_write(int fd, uint32_t handle, uint64_t offset,  const void *buf, uint64_t length);
>  int __gem_read(int fd, uint32_t handle, uint64_t offset, void *buf, uint64_t length);
>  void gem_read(int fd, uint32_t handle, uint64_t offset, void *buf, uint64_t length);
> +bool gem_has_pwrite(int fd);
> +bool gem_has_pread(int fd);
> +void gem_require_pread_pwrite(int fd);
>  int __gem_set_domain(int fd, uint32_t handle, uint32_t read, uint32_t write);
>  void gem_set_domain(int fd, uint32_t handle, uint32_t read, uint32_t write);
>  int gem_wait(int fd, uint32_t handle, int64_t *timeout_ns);
> diff --git a/tests/i915/gem_exec_parallel.c b/tests/i915/gem_exec_parallel.c
> index d3dd06a654..a0469a6438 100644
> --- a/tests/i915/gem_exec_parallel.c
> +++ b/tests/i915/gem_exec_parallel.c
> @@ -204,6 +204,9 @@ static void all(int fd, struct intel_execution_engine2 *engine, unsigned flags)
>      if (flags & CONTEXTS)
>          gem_require_contexts(fd);
>
> +    if (flags & USERPTR)
> +        gem_require_pread_pwrite(fd);
> +
>      if (flags & FDS) {
>          igt_require(gen > 5);
>          igt_require(igt_allow_unlimited_files());
> diff --git a/tests/i915/gem_madvise.c b/tests/i915/gem_madvise.c
> index 623c8b0913..f85c351857 100644
> --- a/tests/i915/gem_madvise.c
> +++ b/tests/i915/gem_madvise.c
> @@ -155,6 +155,7 @@ dontneed_before_pwrite(void)
>      uint32_t bbe = MI_BATCH_BUFFER_END;
>      uint32_t handle;
>
> +    gem_require_pread_pwrite(fd);
>      handle = gem_create(fd, OBJECT_SIZE);
>      gem_madvise(fd, handle, I915_MADV_DONTNEED);
>
> @@ -171,6 +172,7 @@ dontneed_before_exec(void)
>      struct drm_i915_gem_exec_object2 exec;
>      uint32_t buf[] = { MI_BATCH_BUFFER_END, 0 };
>
> +    gem_require_pread_pwrite(fd);
>      memset(&execbuf, 0, sizeof(execbuf));
>      memset(&exec, 0, sizeof(exec));
>
> diff --git a/tests/i915/gem_partial_pwrite_pread.c b/tests/i915/gem_partial_pwrite_pread.c
> index 72c33539d3..5a14d424b2 100644
> --- a/tests/i915/gem_partial_pwrite_pread.c
> +++ b/tests/i915/gem_partial_pwrite_pread.c
> @@ -284,6 +284,7 @@ igt_main
>          data.drm_fd = drm_open_driver(DRIVER_INTEL);
>          igt_require_gem(data.drm_fd);
>          gem_require_blitter(data.drm_fd);
> +        gem_require_pread_pwrite(data.drm_fd);
>
>          data.devid = intel_get_drm_devid(data.drm_fd);
>          data.bops = buf_ops_create(data.drm_fd);
> diff --git a/tests/i915/gem_pread.c b/tests/i915/gem_pread.c
> index 0c4ec0d2fe..ec9991eebd 100644
> --- a/tests/i915/gem_pread.c
> +++ b/tests/i915/gem_pread.c
> @@ -300,6 +300,7 @@ igt_main_args("s:", NULL, help_str, opt_handler, NULL)
>
>      igt_fixture {
>          fd = drm_open_driver(DRIVER_INTEL);
> +        gem_require_pread_pwrite(fd);
>
>          dst = gem_create(fd, object_size);
>          src = malloc(object_size);
> diff --git a/tests/i915/gem_pread_after_blit.c b/tests/i915/gem_pread_after_blit.c
> index f5eba0d50a..3b56f787aa 100644
> --- a/tests/i915/gem_pread_after_blit.c
> +++ b/tests/i915/gem_pread_after_blit.c
> @@ -216,6 +216,7 @@ igt_main
>      igt_fixture {
>          fd = drm_open_driver(DRIVER_INTEL);
>          igt_require_gem(fd);
> +        gem_require_pread_pwrite(fd);
>
>          bops = buf_ops_create(fd);
>
> diff --git a/tests/i915/gem_pwrite.c b/tests/i915/gem_pwrite.c
> index 98bec55821..5fd15e6a8f 100644
> --- a/tests/i915/gem_pwrite.c
> +++ b/tests/i915/gem_pwrite.c
> @@ -488,6 +488,7 @@ igt_main_args("s:", NULL, help_str, opt_handler, NULL)
>
>      igt_fixture {
>          fd = drm_open_driver(DRIVER_INTEL);
> +        gem_require_pread_pwrite(fd);
>
>          dst = gem_create(fd, object_size);
>          src = malloc(object_size);
> diff --git a/tests/i915/gem_pwrite_snooped.c b/tests/i915/gem_pwrite_snooped.c
> index 52ebaec2f2..e6a10747d5 100644
> --- a/tests/i915/gem_pwrite_snooped.c
> +++ b/tests/i915/gem_pwrite_snooped.c
> @@ -133,6 +133,7 @@ igt_simple_main
>      fd = drm_open_driver(DRIVER_INTEL);
>      igt_require_gem(fd);
>      gem_require_blitter(fd);
> +    gem_require_pread_pwrite(fd);
>
>      bops = buf_ops_create(fd);
>
> diff --git a/tests/i915/gem_readwrite.c b/tests/i915/gem_readwrite.c
> index d675810ef2..8a958cc904 100644
> --- a/tests/i915/gem_readwrite.c
> +++ b/tests/i915/gem_readwrite.c
> @@ -85,6 +85,7 @@ igt_main
>
>      igt_fixture {
>          fd = drm_open_driver(DRIVER_INTEL);
> +        gem_require_pread_pwrite(fd);
>
>          handle = gem_create(fd, OBJECT_SIZE);
>      }
> diff --git a/tests/i915/gem_set_tiling_vs_pwrite.c b/tests/i915/gem_set_tiling_vs_pwrite.c
> index 771dd2e136..87909d3c7c 100644
> --- a/tests/i915/gem_set_tiling_vs_pwrite.c
> +++ b/tests/i915/gem_set_tiling_vs_pwrite.c
> @@ -57,6 +57,7 @@ igt_simple_main
>
>      fd = drm_open_driver(DRIVER_INTEL);
>      igt_require(gem_available_fences(fd) > 0);
> +    gem_require_pread_pwrite(fd);
>
>      for (int i = 0; i < OBJECT_SIZE/4; i++)
>          data[i] = i;
> diff --git a/tests/i915/gem_tiled_partial_pwrite_pread.c b/tests/i915/gem_tiled_partial_pwrite_pread.c
> index 4f8f4190b5..95fb69c659 100644
> --- a/tests/i915/gem_tiled_partial_pwrite_pread.c
> +++ b/tests/i915/gem_tiled_partial_pwrite_pread.c
> @@ -280,6 +280,7 @@ igt_main
>          igt_require_gem(fd);
>          gem_require_mappable_ggtt(fd);
>          gem_require_blitter(fd);
> +        gem_require_pread_pwrite(fd);
>
>          bops = buf_ops_create(fd);
>
> diff --git a/tests/i915/gem_tiled_pread_basic.c b/tests/i915/gem_tiled_pread_basic.c
> index 862714140a..186f630f7d 100644
> --- a/tests/i915/gem_tiled_pread_basic.c
> +++ b/tests/i915/gem_tiled_pread_basic.c
> @@ -128,6 +128,7 @@ igt_simple_main
>      igt_require(gem_available_fences(fd) > 0);
>      handle = create_bo(fd);
>      igt_require(gem_get_tiling(fd, handle, &tiling, &swizzle));
> +    gem_require_pread_pwrite(fd);
>
>      devid = intel_get_drm_devid(fd);
>
> diff --git a/tests/i915/gem_tiled_pread_pwrite.c b/tests/i915/gem_tiled_pread_pwrite.c
> index b73fa12626..ef1e1b3c3c 100644
> --- a/tests/i915/gem_tiled_pread_pwrite.c
> +++ b/tests/i915/gem_tiled_pread_pwrite.c
> @@ -114,6 +114,7 @@ igt_simple_main
>
>      fd = drm_open_driver(DRIVER_INTEL);
>      igt_require(gem_available_fences(fd) > 0);
> +    gem_require_pread_pwrite(fd);
>
>      count = gem_available_fences(fd) + 1;
>      intel_require_memory(2 * count, sizeof(linear), CHECK_RAM);
> diff --git a/tests/i915/gem_userptr_blits.c b/tests/i915/gem_userptr_blits.c
> index 8765123e09..ded761a550 100644
> --- a/tests/i915/gem_userptr_blits.c
> +++ b/tests/i915/gem_userptr_blits.c
> @@ -1137,6 +1137,7 @@ static int test_forbidden_ops(int fd)
>      uint32_t handle;
>      void *ptr;
>
> +    gem_require_pread_pwrite(fd);
>      igt_assert(posix_memalign(&ptr, PAGE_SIZE, PAGE_SIZE) == 0);
>      gem_userptr(fd, ptr, PAGE_SIZE, 0, userptr_flags, &handle);
>
> @@ -1664,6 +1665,7 @@ static void test_readonly_pwrite(int i915)
>       */
>
>      igt_require(igt_setup_clflush());
> +    gem_require_pread_pwrite(i915);
>
>      sz = 16 << 12;
>      pages = mmap(NULL, sz, PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
> diff --git a/tests/i915/gen9_exec_parse.c b/tests/i915/gen9_exec_parse.c
> index 6f54c4e133..f9de90d2cf 100644
> --- a/tests/i915/gen9_exec_parse.c
> +++ b/tests/i915/gen9_exec_parse.c
> @@ -1235,8 +1235,10 @@ igt_main
>                 -EINVAL);
>      }
>
> -    igt_subtest("batch-invalid-length")
> +    igt_subtest("batch-invalid-length") {
> +        gem_require_pread_pwrite(i915);
>          test_invalid_length(i915, handle);
> +    }
>
>      igt_subtest("basic-rejected")
>          test_rejected(i915, handle, false);
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