Re: [Intel-gfx] [PATCH v2 5/5] tools/testing/scatterlist: Test new __sg_alloc_table_from_pages

[Tvrtko Ursulin]

On 06/09/2017 11:48, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2017-09-05 11:24:03)
> > From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> >
> > Exercise the new __sg_alloc_table_from_pages API (and through
> > it also the old sg_alloc_table_from_pages), checking that the
> > created table has the expected number of segments depending on
> > the sequence of input pages and other conditions.
> >
> > v2: Move to data driven for readability.
> >
> > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > ---
> >   tools/testing/scatterlist/Makefile   |  30 +++++++++
> >   tools/testing/scatterlist/linux/mm.h | 125 +++++++++++++++++++++++++++++++++++
> >   tools/testing/scatterlist/main.c     |  74 +++++++++++++++++++++
> >   3 files changed, 229 insertions(+)
> >   create mode 100644 tools/testing/scatterlist/Makefile
> >   create mode 100644 tools/testing/scatterlist/linux/mm.h
> >   create mode 100644 tools/testing/scatterlist/main.c
> >
> > diff --git a/tools/testing/scatterlist/Makefile b/tools/testing/scatterlist/Makefile
> > new file mode 100644
> > index 000000000000..0867e0ef32d6
> > --- /dev/null
> > +++ b/tools/testing/scatterlist/Makefile
> > @@ -0,0 +1,30 @@
> > +CFLAGS += -I. -I../../include -g -O2 -Wall -fsanitize=address
> > +LDFLAGS += -fsanitize=address
> > +TARGETS = main
> > +OFILES = main.o scatterlist.o
> > +
> > +ifeq ($(BUILD), 32)
> > +        CFLAGS += -m32
> > +        LDFLAGS += -m32
> > +endif
>
> Hmm, are there no HOST_CFLAGS? No. I wonder how menuconfig/xconfig get
> compiled.
>
> HOSTCC, HOSTCFLAGS.
>
> hostprogs-y := main
> always := $(hostprogs-y)
>
> But nothing else seems to use HOSTCC in testing/selftests

I lifted it frim an existing makefile. I think this means no one was 
interested in building tests while doing a cross compile.

> > +targets: include $(TARGETS)
> > +
> > +main: $(OFILES)
> > +
> > +clean:
> > +       $(RM) $(TARGETS) $(OFILES) scatterlist.c linux/scatterlist.h linux/highmem.h linux/kmemleak.h asm/io.h
> > +       @rmdir asm
> > +
> > +scatterlist.c: ../../../lib/scatterlist.c
> > +       @sed -e 's/^static //' -e 's/__always_inline //' -e 's/inline //' < $< > $@
>
> I think I would have used
>
> #define __always_inline inline
> #include "../../../lib/scatterlist.c"

Again, I lifted the approach from one of the existing tests. It might be 
beneficial to have a local copy when debugging, but it is probably very 
marginal and both approaches look OK.

> > diff --git a/tools/testing/scatterlist/main.c b/tools/testing/scatterlist/main.c
> > new file mode 100644
> > index 000000000000..8ca5c8703eb7
> > --- /dev/null
> > +++ b/tools/testing/scatterlist/main.c
> > @@ -0,0 +1,74 @@
> > +#include <stdio.h>
> > +#include <assert.h>
> > +
> > +#include <linux/scatterlist.h>
> > +
> > +#define MAX_PAGES (64)
> > +
> > +static void set_pages(struct page **pages, const unsigned *array, unsigned num)
> > +{
> > +       unsigned int i;
> > +
> > +       assert(num < MAX_PAGES);
> > +       for (i = 0; i < num; i++)
> > +               pages[i] = (struct page *)(unsigned long)
> > +                          ((1 + array[i]) * PAGE_SIZE);
>
> pfn_to_page(PFN_BIAS + array[i]) ? Ah, that relies on headers. Ok.
>
> > +}
> > +
> > +#define pfn(...) (unsigned []){ __VA_ARGS__ }
> > +
> > +int main(void)
> > +{
> > +       const unsigned int sgmax = SCATTERLIST_MAX_SEGMENT;
> > +       struct test {
> > +               int alloc_ret;
> > +               unsigned num_pages;
> > +               unsigned *pfn;
> > +               unsigned size;
> > +               unsigned int max_seg;
> > +               unsigned int expected_segments;
> > +       } *test, tests[] = {
> > +               { -EINVAL, 1, pfn(0), PAGE_SIZE, PAGE_SIZE + 1, 1 },
> > +               { -EINVAL, 1, pfn(0), PAGE_SIZE, 0, 1 },
> > +               { -EINVAL, 1, pfn(0), PAGE_SIZE, sgmax + 1, 1 },
> > +               { 0, 1, pfn(0), PAGE_SIZE, sgmax, 1 },
> > +               { 0, 1, pfn(0), 1, sgmax, 1 },
> > +               { 0, 2, pfn(0, 1), 2 * PAGE_SIZE, sgmax, 1 },
> > +               { 0, 3, pfn(0, 1, 3), 3 * PAGE_SIZE, sgmax, 2 },
> > +               { 0, 4, pfn(0, 1, 3, 4), 4 * PAGE_SIZE, sgmax, 2 },
> > +               { 0, 5, pfn(0, 1, 3, 4, 5), 5 * PAGE_SIZE, sgmax, 2 },
> > +               { 0, 5, pfn(0, 1, 3, 4, 6), 5 * PAGE_SIZE, sgmax, 3 },
> > +               { 0, 5, pfn(0, 1, 2, 3, 4), 5 * PAGE_SIZE, sgmax, 1 },
> > +               { 0, 5, pfn(0, 1, 2, 3, 4), 5 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
> > +               { 0, 6, pfn(0, 1, 2, 3, 4, 5), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
> > +               { 0, 6, pfn(0, 2, 3, 4, 5, 6), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 4 },
> > +               { 0, 6, pfn(0, 1, 3, 4, 5, 6), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
>
> All ascending. Interesting challenge for 3,2,1,0; it can be coalesced,
> we just don't. I wonder if we are missing some like that. But for the

Hm, how do you think descending pages could be coalesced? By 
re-arranging the pages? But that would break everything, do I don't get it.

> moment, 0, 2, 1, would be a good addition to the above set.
>
> Is there any value in checking overflows in this interface?

Overflows as in size > num_pages * PAGE_SIZE as passed in to 
__sg_alloc_table_from_pages ? It is not checked in the implementation at 
the moment and it looks it is harmless.

There is one test above which checks for underflow (size < num_pages * 
PAGE_SIZE).

> Lgtm, throw in a couple of inverted positions,
> Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

Will do, thanks!

Regards,

Tvrtko