Re: [PATCH v4 03/10] KVM: selftests: Read binary stats desc in lib

[Ben Gardon]

On Tue, Apr 12, 2022 at 1:03 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> On Tue, Apr 12, 2022, Sean Christopherson wrote:
> > On Tue, Apr 12, 2022, Ben Gardon wrote:
> > > On Mon, Apr 11, 2022 at 5:55 PM Mingwei Zhang <mizhang@xxxxxxxxxx> wrote:
> > > > I was very confused on header->name_size. So this field means the
> > > > maximum string size of a stats name, right? Can we update the comments
> > > > in the kvm.h to specify that? By reading the comments, I don't really
> > > > feel this is how we should use this field.
> > >
> > > I believe that's right. I agree the documentation on that was a little
> > > confusing.
> >
> > Heh, a little.  I got tripped up looking at this too.  Give me a few minutes and
> > I'll attach a cleanup patch to add comments and fix the myriad style issues.
> >
> > This whole file is painful to look at.  Aside from violating preferred kernel
> > style, it's horribly consistent with itself.  Well, except for the 80 char limit,
> > to which it has a fanatical devotion.
>
> If you send a new version of this series, can you add this on top?

Will do.

>
> From: Sean Christopherson <seanjc@xxxxxxxxxx>
> Date: Tue, 12 Apr 2022 11:49:59 -0700
> Subject: [PATCH] KVM: selftests: Clean up coding style in binary stats test
>
> Fix a variety of code style violations and/or inconsistencies in the
> binary stats test.  The 80 char limit is a soft limit and can and should
> be ignored/violated if doing so improves the overall code readability.
>
> Specifically, provide consistent indentation and don't split expressions
> at arbitrary points just to honor the 80 char limit.
>
> Opportunistically expand/add comments to call out the more subtle aspects
> of the code.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
>  .../selftests/kvm/kvm_binary_stats_test.c     | 91 ++++++++++++-------
>  1 file changed, 56 insertions(+), 35 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/kvm_binary_stats_test.c b/tools/testing/selftests/kvm/kvm_binary_stats_test.c
> index 97b180249ba0..944ed52e3f07 100644
> --- a/tools/testing/selftests/kvm/kvm_binary_stats_test.c
> +++ b/tools/testing/selftests/kvm/kvm_binary_stats_test.c
> @@ -37,32 +37,42 @@ static void stats_test(int stats_fd)
>         /* Read kvm stats header */
>         read_vm_stats_header(stats_fd, &header);
>
> +       /*
> +        * The base size of the descriptor is defined by KVM's ABI, but the
> +        * size of the name field is variable as far as KVM's ABI is concerned.
> +        * But, the size of name is constant for a given instance of KVM and
> +        * is provided by KVM in the overall stats header.
> +        */
>         size_desc = sizeof(*stats_desc) + header.name_size;
>
>         /* Read kvm stats id string */
>         id = malloc(header.name_size);
>         TEST_ASSERT(id, "Allocate memory for id string");
> +
>         ret = read(stats_fd, id, header.name_size);
>         TEST_ASSERT(ret == header.name_size, "Read id string");
>
>         /* Check id string, that should start with "kvm" */
>         TEST_ASSERT(!strncmp(id, "kvm", 3) && strlen(id) < header.name_size,
> -                               "Invalid KVM stats type, id: %s", id);
> +                   "Invalid KVM stats type, id: %s", id);
>
>         /* Sanity check for other fields in header */
>         if (header.num_desc == 0) {
>                 printf("No KVM stats defined!");
>                 return;
>         }
> -       /* Check overlap */
> -       TEST_ASSERT(header.desc_offset > 0 && header.data_offset > 0
> -                       && header.desc_offset >= sizeof(header)
> -                       && header.data_offset >= sizeof(header),
> -                       "Invalid offset fields in header");
> +       /*
> +        * The descriptor and data offsets must be valid, they must not overlap
> +        * the header, and the descriptor and data blocks must not overlap each
> +        * other.  Note, the data block is rechecked after its size is known.
> +        */
> +       TEST_ASSERT(header.desc_offset && header.desc_offset >= sizeof(header) &&
> +                   header.data_offset && header.data_offset >= sizeof(header),
> +                   "Invalid offset fields in header");
> +
>         TEST_ASSERT(header.desc_offset > header.data_offset ||
> -                       (header.desc_offset + size_desc * header.num_desc <=
> -                                                       header.data_offset),
> -                       "Descriptor block is overlapped with data block");
> +                   (header.desc_offset + size_desc * header.num_desc <= header.data_offset),
> +                   "Descriptor block is overlapped with data block");
>
>         /* Read kvm stats descriptors */
>         stats_desc = alloc_vm_stats_desc(stats_fd, &header);
> @@ -70,15 +80,22 @@ static void stats_test(int stats_fd)
>
>         /* Sanity check for fields in descriptors */
>         for (i = 0; i < header.num_desc; ++i) {
> +               /*
> +                * Note, size_desc includes the of the name field, which is
> +                * variable, i.e. this is NOT equivalent to &stats_desc[i].
> +                */
>                 pdesc = (void *)stats_desc + i * size_desc;
> -               /* Check type,unit,base boundaries */
> -               TEST_ASSERT((pdesc->flags & KVM_STATS_TYPE_MASK)
> -                               <= KVM_STATS_TYPE_MAX, "Unknown KVM stats type");
> -               TEST_ASSERT((pdesc->flags & KVM_STATS_UNIT_MASK)
> -                               <= KVM_STATS_UNIT_MAX, "Unknown KVM stats unit");
> -               TEST_ASSERT((pdesc->flags & KVM_STATS_BASE_MASK)
> -                               <= KVM_STATS_BASE_MAX, "Unknown KVM stats base");
> -               /* Check exponent for stats unit
> +
> +               /* Check type, unit, and base boundaries */
> +               TEST_ASSERT((pdesc->flags & KVM_STATS_TYPE_MASK) <= KVM_STATS_TYPE_MAX,
> +                           "Unknown KVM stats type");
> +               TEST_ASSERT((pdesc->flags & KVM_STATS_UNIT_MASK) <= KVM_STATS_UNIT_MAX,
> +                           "Unknown KVM stats unit");
> +               TEST_ASSERT((pdesc->flags & KVM_STATS_BASE_MASK) <= KVM_STATS_BASE_MAX,
> +                           "Unknown KVM stats base");
> +
> +               /*
> +                * Check exponent for stats unit
>                  * Exponent for counter should be greater than or equal to 0
>                  * Exponent for unit bytes should be greater than or equal to 0
>                  * Exponent for unit seconds should be less than or equal to 0
> @@ -89,47 +106,51 @@ static void stats_test(int stats_fd)
>                 case KVM_STATS_UNIT_NONE:
>                 case KVM_STATS_UNIT_BYTES:
>                 case KVM_STATS_UNIT_CYCLES:
> -                       TEST_ASSERT(pdesc->exponent >= 0,
> -                                       "Unsupported KVM stats unit");
> +                       TEST_ASSERT(pdesc->exponent >= 0, "Unsupported KVM stats unit");
>                         break;
>                 case KVM_STATS_UNIT_SECONDS:
> -                       TEST_ASSERT(pdesc->exponent <= 0,
> -                                       "Unsupported KVM stats unit");
> +                       TEST_ASSERT(pdesc->exponent <= 0, "Unsupported KVM stats unit");
>                         break;
>                 }
>                 /* Check name string */
>                 TEST_ASSERT(strlen(pdesc->name) < header.name_size,
> -                               "KVM stats name(%s) too long", pdesc->name);
> +                           "KVM stats name(%s) too long", pdesc->name);
>                 /* Check size field, which should not be zero */
> -               TEST_ASSERT(pdesc->size, "KVM descriptor(%s) with size of 0",
> -                               pdesc->name);
> +               TEST_ASSERT(pdesc->size,
> +                           "KVM descriptor(%s) with size of 0", pdesc->name);
>                 /* Check bucket_size field */
>                 switch (pdesc->flags & KVM_STATS_TYPE_MASK) {
>                 case KVM_STATS_TYPE_LINEAR_HIST:
>                         TEST_ASSERT(pdesc->bucket_size,
> -                           "Bucket size of Linear Histogram stats (%s) is zero",
> -                           pdesc->name);
> +                                   "Bucket size of Linear Histogram stats (%s) is zero",
> +                                   pdesc->name);
>                         break;
>                 default:
>                         TEST_ASSERT(!pdesc->bucket_size,
> -                           "Bucket size of stats (%s) is not zero",
> -                           pdesc->name);
> +                                   "Bucket size of stats (%s) is not zero",
> +                                   pdesc->name);
>                 }
>                 size_data += pdesc->size * sizeof(*stats_data);
>         }
> -       /* Check overlap */
> -       TEST_ASSERT(header.data_offset >= header.desc_offset
> -               || header.data_offset + size_data <= header.desc_offset,
> -               "Data block is overlapped with Descriptor block");
> +
> +       /*
> +        * Now that the size of the data block is known, verify the data block
> +        * doesn't overlap the descriptor block.
> +        */
> +       TEST_ASSERT(header.data_offset >= header.desc_offset ||
> +                   header.data_offset + size_data <= header.desc_offset,
> +                   "Data block is overlapped with Descriptor block");
> +
>         /* Check validity of all stats data size */
>         TEST_ASSERT(size_data >= header.num_desc * sizeof(*stats_data),
> -                       "Data size is not correct");
> +                   "Data size is not correct");
> +
>         /* Check stats offset */
>         for (i = 0; i < header.num_desc; ++i) {
>                 pdesc = (void *)stats_desc + i * size_desc;
>                 TEST_ASSERT(pdesc->offset < size_data,
> -                       "Invalid offset (%u) for stats: %s",
> -                       pdesc->offset, pdesc->name);
> +                           "Invalid offset (%u) for stats: %s",
> +                           pdesc->offset, pdesc->name);
>         }
>
>         /* Read kvm stats data one by one */
>
> base-commit: f9955a6aaa037a7a8198a817b9d272efcf10961a
> --
>