On Sun, 17 Feb 2019 at 20:27, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
>
> Quoting Matthew Auld (2019-02-17 18:35:05)
> > On Thu, 14 Feb 2019 at 18:32, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
> > >
> > > The kernel must not return stale information back to userspace when they
> > > create a new object. For that purpose, we always clear objects on
> > > creation, so verify that this is so.
> > >
> > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > > Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
> > > ---
> > > tests/i915/gem_create.c | 71 +++++++++++++++++++++++++++++++++++++++++
> > > 1 file changed, 71 insertions(+)
> > >
> > > diff --git a/tests/i915/gem_create.c b/tests/i915/gem_create.c
> > > index 25c5e8088..9de2263d5 100644
> > > --- a/tests/i915/gem_create.c
> > > +++ b/tests/i915/gem_create.c
> > > @@ -44,6 +44,7 @@
> > > #include <sys/stat.h>
> > > #include <sys/time.h>
> > > #include <getopt.h>
> > > +#include <pthread.h>
> > >
> > > #include <drm.h>
> > >
> > > @@ -141,6 +142,73 @@ static void invalid_nonaligned_size(int fd)
> > > gem_close(fd, handle);
> > > }
> > >
> > > +static uint64_t get_npages(uint64_t *global, uint64_t npages)
> > > +{
> > > + uint64_t try, old, max;
> > > +
> > > + max = *global;
> > > + do {
> > > + old = max;
> > > + try = npages % (max / 2);
> > > + max -= try;
> > > + } while ((max = __sync_val_compare_and_swap(global, old, max)) != old);
> > > +
> > > + return try;
> > > +}
> > > +
> > > +struct thread_clear {
> > > + uint64_t max;
> > > + int timeout;
> > > + int i915;
> > > +};
> > > +
> > > +static void *thread_clear(void *data)
> > > +{
> > > + struct thread_clear *arg = data;
> > > + int i915 = arg->i915;
> > > +
> > > + igt_until_timeout(arg->timeout) {
> > > + uint32_t handle;
> > > + uint64_t npages;
> > > +
> > > + npages = random();
> > > + npages <<= 32;
> > > + npages |= random();
> > > + npages = get_npages(&arg->max, npages);
> > > +
> > > + handle = gem_create(i915, npages << 12);
> > > + for (uint64_t page = 0; page < npages; page++) {
> > > + uint64_t x;
> > > +
> > > + gem_read(i915, handle,
> > > + page % (4096 - sizeof(x)),
> > > + &x, sizeof(x));
> >
> > Don't we also want to read some values outside of the first page, or
> > am I missing something?
>
> No it was meant to be advancing each page, and then byte within page.
>
> With the trivial page * 4096 + ...?
Yup, r-b.
> -Chris
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