Re: [PATCH v2 2/2] tests: migration-test: Add dirty ring test

[Juan Quintela]

Peter Xu <peterx@redhat.com> wrote:
> Add dirty ring test if kernel supports it.  Add the dirty ring parameter on
> source should be mostly enough, but let's change the dest too to make them
> match always.
>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Why we check with 4096 and not whatever the kernel returs?

So ....

> @@ -467,6 +471,8 @@ typedef struct {
>      bool use_shmem;
>      /* only launch the target process */
>      bool only_target;
> +    /* Use dirty ring if true; dirty logging otherwise */
> +    bool use_dirty_ring;

make this an int

>      char *opts_source;
>      char *opts_target;
>  } MigrateStart;
> @@ -573,11 +579,13 @@ static int test_migrate_start(QTestState **from, 
> QTestState **to,
>          shmem_opts = g_strdup("");
>      }
>  
> -    cmd_source = g_strdup_printf("-accel kvm -accel tcg%s%s "
> +    cmd_source = g_strdup_printf("-accel kvm%s -accel tcg%s%s "
>                                   "-name source,debug-threads=on "
>                                   "-m %s "
>                                   "-serial file:%s/src_serial "
>                                   "%s %s %s %s",
> +                                 args->use_dirty_ring ?
> +                                 ",dirty-ring-size=4096" : "",

check if it is > 0 here and otherwise pass it

>                                   machine_opts ? " -machine " : "",
>                                   machine_opts ? machine_opts : "",
>                                   memory_size, tmpfs,
> @@ -587,12 +595,14 @@ static int test_migrate_start(QTestState **from, 
> QTestState **to,
>          *from = qtest_init(cmd_source);

> +static bool kvm_dirty_ring_supported(void)
> +{
> +#if defined(__linux__)
> +    int ret, kvm_fd = open("/dev/kvm", O_RDONLY);
> +
> +    if (kvm_fd < 0) {
> +        return false;
> +    }
> +
> +    ret = ioctl(kvm_fd, KVM_CHECK_EXTENSION, KVM_CAP_DIRTY_LOG_RING);
> +    close(kvm_fd);
> +
> +    /* We test with 4096 slots */
> +    if (ret < 4096) {

And we return this value.

> +        return false;
> +    }
> +
> +    return true;
> +#else
> +    return false;
> +#endif
> +}

Mental note, don't we have a function inside tests/ that check if
a kvm feauture is there?

Quick check seems to imply no.

On the other hand, KVM_CHECK_EXTENSION is basically only used on
kvm-all.c

Later, Juan.