Re: [PATCH v2 02/10] KVM: selftests: simplify setup_demand_paging error handling

[Ben Gardon]

On Wed, May 19, 2021 at 3:14 PM Axel Rasmussen <axelrasmussen@xxxxxxxxxx> wrote:
>
> On Wed, May 19, 2021 at 2:45 PM Ben Gardon <bgardon@xxxxxxxxxx> wrote:
> >
> > On Wed, May 19, 2021 at 1:03 PM Axel Rasmussen <axelrasmussen@xxxxxxxxxx> wrote:
> > >
> > > A small cleanup. Our caller writes:
> > >
> > >   r = setup_demand_paging(...);
> > >   if (r < 0) exit(-r);
> > >
> > > Since we're just going to exit anyway, instead of returning an error we
> > > can just re-use TEST_ASSERT. This makes the caller simpler, as well as
> > > the function itself - no need to write our branches, etc.
> > >
> > > Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>

Reviewed-by: Ben Gardon <bgardon@xxxxxxxxxx>

> > > ---
> > >  .../selftests/kvm/demand_paging_test.c        | 51 +++++++------------
> > >  1 file changed, 19 insertions(+), 32 deletions(-)
> > >
> > > diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
> > > index 9398ba6ef023..601a1df24dd2 100644
> > > --- a/tools/testing/selftests/kvm/demand_paging_test.c
> > > +++ b/tools/testing/selftests/kvm/demand_paging_test.c
> > > @@ -9,6 +9,8 @@
> > >
> > >  #define _GNU_SOURCE /* for pipe2 */
> > >
> > > +#include <inttypes.h>
> > > +#include <stdint.h>
> >
> > Why do the includes need to change in this commit? Is it for the PRIu64 below?
>
> Right, I didn't actually try compiling without these, but inttypes.h
> defines PRIu64 and stdint.h defines uint64_t. In general I tend to
> prefer including things like this because we're using their
> definitions directly, even if we might be picking them up transiently
> some other way.

Makes sense to me.

>
> >
> > >  #include <stdio.h>
> > >  #include <stdlib.h>
> > >  #include <time.h>
> > > @@ -198,42 +200,32 @@ static void *uffd_handler_thread_fn(void *arg)
> > >         return NULL;
> > >  }
> > >
> > > -static int setup_demand_paging(struct kvm_vm *vm,
> > > -                              pthread_t *uffd_handler_thread, int pipefd,
> > > -                              useconds_t uffd_delay,
> > > -                              struct uffd_handler_args *uffd_args,
> > > -                              void *hva, uint64_t len)
> > > +static void setup_demand_paging(struct kvm_vm *vm,
> > > +                               pthread_t *uffd_handler_thread, int pipefd,
> > > +                               useconds_t uffd_delay,
> > > +                               struct uffd_handler_args *uffd_args,
> > > +                               void *hva, uint64_t len)
> > >  {
> > >         int uffd;
> > >         struct uffdio_api uffdio_api;
> > >         struct uffdio_register uffdio_register;
> > >
> > >         uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
> > > -       if (uffd == -1) {
> > > -               pr_info("uffd creation failed\n");
> > > -               return -1;
> > > -       }
> > > +       TEST_ASSERT(uffd >= 0, "uffd creation failed, errno: %d", errno);
> > >
> > >         uffdio_api.api = UFFD_API;
> > >         uffdio_api.features = 0;
> > > -       if (ioctl(uffd, UFFDIO_API, &uffdio_api) == -1) {
> > > -               pr_info("ioctl uffdio_api failed\n");
> > > -               return -1;
> > > -       }
> > > +       TEST_ASSERT(ioctl(uffd, UFFDIO_API, &uffdio_api) != -1,
> > > +                   "ioctl UFFDIO_API failed: %" PRIu64,
> > > +                   (uint64_t)uffdio_api.api);
> > >
> > >         uffdio_register.range.start = (uint64_t)hva;
> > >         uffdio_register.range.len = len;
> > >         uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
> > > -       if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register) == -1) {
> > > -               pr_info("ioctl uffdio_register failed\n");
> > > -               return -1;
> > > -       }
> > > -
> > > -       if ((uffdio_register.ioctls & UFFD_API_RANGE_IOCTLS) !=
> > > -                       UFFD_API_RANGE_IOCTLS) {
> > > -               pr_info("unexpected userfaultfd ioctl set\n");
> > > -               return -1;
> > > -       }
> > > +       TEST_ASSERT(ioctl(uffd, UFFDIO_REGISTER, &uffdio_register) != -1,
> > > +                   "ioctl UFFDIO_REGISTER failed");
> > > +       TEST_ASSERT((uffdio_register.ioctls & UFFD_API_RANGE_IOCTLS) ==
> > > +                   UFFD_API_RANGE_IOCTLS, "unexpected userfaultfd ioctl set");
> > >
> > >         uffd_args->uffd = uffd;
> > >         uffd_args->pipefd = pipefd;
> > > @@ -243,8 +235,6 @@ static int setup_demand_paging(struct kvm_vm *vm,
> > >
> > >         PER_VCPU_DEBUG("Created uffd thread for HVA range [%p, %p)\n",
> > >                        hva, hva + len);
> > > -
> > > -       return 0;
> > >  }
> > >
> > >  struct test_params {
> > > @@ -321,13 +311,10 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> > >                                   O_CLOEXEC | O_NONBLOCK);
> > >                         TEST_ASSERT(!r, "Failed to set up pipefd");
> > >
> > > -                       r = setup_demand_paging(vm,
> > > -                                               &uffd_handler_threads[vcpu_id],
> > > -                                               pipefds[vcpu_id * 2],
> > > -                                               p->uffd_delay, &uffd_args[vcpu_id],
> > > -                                               vcpu_hva, vcpu_mem_size);
> > > -                       if (r < 0)
> > > -                               exit(-r);
> > > +                       setup_demand_paging(vm, &uffd_handler_threads[vcpu_id],
> > > +                                           pipefds[vcpu_id * 2], p->uffd_delay,
> > > +                                           &uffd_args[vcpu_id], vcpu_hva,
> > > +                                           vcpu_mem_size);
> > >                 }
> > >         }
> > >
> > > --
> > > 2.31.1.751.gd2f1c929bd-goog
> > >