Re: [PATCH 5/6] KVM: selftests: memslot_perf_test: Consolidate memory sizes

[Gavin Shan]

On 10/18/22 5:36 AM, Maciej S. Szmigiero wrote:
> On 14.10.2022 09:19, Gavin Shan wrote:
> > The addresses and sizes passed to madvise() and vm_userspace_mem_region_add()
> > should be aligned to host page size, which can be 64KB on aarch64. So it's
> > wrong by passing additional fixed 4KB memory area to various tests.
> >
> > Fix it by passing additional fixed 64KB memory area to various tests. After
> > it's applied, the following command works fine on 64KB-page-size-host and
> > 4KB-page-size-guest.
> >
> >    # ./memslot_perf_test -v -s 512
> >
> > Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
> > ---
> >   .../testing/selftests/kvm/memslot_perf_test.c  | 18 ++++++++++--------
> >   1 file changed, 10 insertions(+), 8 deletions(-)
> >
> > diff --git a/tools/testing/selftests/kvm/memslot_perf_test.c b/tools/testing/selftests/kvm/memslot_perf_test.c
> > index d587bd952ff9..e6d34744b45d 100644
> > --- a/tools/testing/selftests/kvm/memslot_perf_test.c
> > +++ b/tools/testing/selftests/kvm/memslot_perf_test.c
> > @@ -25,12 +25,14 @@
> >   #include <kvm_util.h>
> >   #include <processor.h>
> > -#define MEM_SIZE        ((512U << 20) + 4096)
> > -#define MEM_GPA        0x10000000UL
> > +#define MEM_EXTRA_SIZE        0x10000
>
> So the biggest page size supported right now is 64 KiB - it would be
> good to have an assert somewhere to explicitly check for this
> (regardless of implicit checks present in other calculations).
>
> Also, an expression like "(64 << 10)" is more readable than a "1"
> with a tail of zeroes (it's easy to add one zero too many or be one
> zero short).

Yes, it makes sense to me. Lets add check in check_memory_sizes(), which
was added in the previous patch, to fail early if host/guest page size
exceeds 64KB.

   if (host_page_size > SIZE_64KiB || guest_page_size > SIZE_64KiB) {
      pr_info("Unsupported page size on host (0x%x) or guest (0x%x)\n",
              host_page_size, guest_page_size);
   }


For the macros, I think all of us agree on KiB, MiB, GiB, TiB and
their variants :)

Thanks,
Gavin