Re: [PATCH] qemu: Reject updating unsupported disk information

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On Thu, Jul 09, 2015 at 18:36:00 +0200, Martin Kletzander wrote:
> If one calls update-device with information that is not updatable,
> libvirt reports success even though no data were updated.  The example
> used in the bug linked below uses updating device with <boot order='2'/>
> which, in my opinion, is a valid thing to request from user's
> perspective.  Mainly since we properly error out if user wants to update
> such data on a network device for example.
> 
> And since there are many things that might happen (update-device on disk
> basically knows just how to change removable media), check for what's
> changing and moreover, since the function might be usable in other
> dirvers (updating only disk path is a valid possibility) let's abstract
> it for any two disks.
> 
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1007228
> ---
>  src/conf/domain_conf.c   | 111 +++++++++++++++++++++++++++++++++++++++++++++++
>  src/conf/domain_conf.h   |   2 +
>  src/libvirt_private.syms |   1 +
>  src/qemu/qemu_driver.c   |   3 ++
>  4 files changed, 117 insertions(+)
> 
> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index 0219c3c4814d..a6950087d987 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -5687,6 +5687,117 @@ virDomainDiskFindByBusAndDst(virDomainDefPtr def,
>      return NULL;
>  }
> 
> +
> +/*
> + * Makes sure the @disk differs from @orig_disk only by the source
> + * path and nothing else.  Fields that are being checked and the
> + * information whether they are nullable (can be NULL) or is taken

Um, NULL? see below ...

> + * from the virDomainDiskDefFormat() code.
> + */
> +bool
> +virDomainDiskDiffersSourceOnly(virDomainDiskDefPtr disk,
> +                               virDomainDiskDefPtr orig_disk)
> +{
> +#define CHECK_EQ(field, field_name, nullable)                           \
> +    do {                                                                \
> +        if (nullable && !disk->field)                                   \
> +            break;                                                      \
> +        if (disk->field != orig_disk->field) {                          \
> +            virReportError(VIR_ERR_OPERATION_UNSUPPORTED,               \
> +                           _("cannot modify field '%s' of the disk"),   \
> +                           field_name);                                 \
> +            return false;                                               \
> +        }                                                               \
> +    } while (0)
> +
> +    CHECK_EQ(device, "device", false);
> +    CHECK_EQ(cachemode, "cache", true);

Lets take the line below as an example.

> +    CHECK_EQ(error_policy, "error_policy", true);

If disk->error_policy == VIR_DOMAIN_DISK_ERROR_POLICY_DEFAULT (which
equals to 0) the check will be skipped and thus the error_policy setting
might be different and we would not report an error.

> +    CHECK_EQ(rerror_policy, "rerror_policy", true);
> +    CHECK_EQ(iomode, "io", true);
> +    CHECK_EQ(ioeventfd, "ioeventfd", true);
> +    CHECK_EQ(event_idx, "event_idx", true);
> +    CHECK_EQ(copy_on_read, "copy_on_read", true);
> +    CHECK_EQ(discard, "discard", true);
> +    CHECK_EQ(iothread, "iothread", true);
> +
> +    if (disk->geometry.cylinders &&
> +        disk->geometry.heads &&
> +        disk->geometry.sectors) {
> +        CHECK_EQ(geometry.cylinders, "geometry cylinders", false);
> +        CHECK_EQ(geometry.heads, "geometry heads", false);
> +        CHECK_EQ(geometry.sectors, "geometry sectors", false);
> +        CHECK_EQ(geometry.trans, "BIOS-translation-modus", true);
> +    }
> +
> +    CHECK_EQ(blockio.logical_block_size,
> +             "blockio logical_block_size", false);
> +    CHECK_EQ(blockio.physical_block_size,
> +             "blockio physical_block_size", false);
> +
> +    if (disk->bus == VIR_DOMAIN_DISK_BUS_USB)
> +        CHECK_EQ(removable, "removable", true);
> +

As an example of the field below. The field is an integer ... 

> +    CHECK_EQ(blkdeviotune.total_bytes_sec,
> +             "blkdeviotune.total_bytes_sec",
> +             true);
> +    CHECK_EQ(blkdeviotune.read_bytes_sec,
> +             "blkdeviotune.read_bytes_sec",
> +             true);
> +    CHECK_EQ(blkdeviotune.write_bytes_sec,
> +             "blkdeviotune.write_bytes_sec",
> +             true);
> +    CHECK_EQ(blkdeviotune.total_iops_sec,
> +             "blkdeviotune.total_iops_sec",
> +             true);
> +    CHECK_EQ(blkdeviotune.read_iops_sec,
> +             "blkdeviotune.read_iops_sec",
> +             true);
> +    CHECK_EQ(blkdeviotune.write_iops_sec,
> +             "blkdeviotune.write_iops_sec",
> +             true);
> +    CHECK_EQ(blkdeviotune.total_bytes_sec_max,
> +             "blkdeviotune.total_bytes_sec_max",
> +             true);
> +    CHECK_EQ(blkdeviotune.read_bytes_sec_max,
> +             "blkdeviotune.read_bytes_sec_max",

All of the usage of CHECK_EQ use the same text in the error message as
is the field name. You could perhaps use the strigification macro
operator.

> +             true);
> +    CHECK_EQ(blkdeviotune.write_bytes_sec_max,
> +             "blkdeviotune.write_bytes_sec_max",
> +             true);
> +    CHECK_EQ(blkdeviotune.total_iops_sec_max,
> +             "blkdeviotune.total_iops_sec_max",
> +             true);
> +    CHECK_EQ(blkdeviotune.read_iops_sec_max,
> +             "blkdeviotune.read_iops_sec_max",
> +             true);
> +    CHECK_EQ(blkdeviotune.write_iops_sec_max,
> +             "blkdeviotune.write_iops_sec_max",
> +             true);
> +    CHECK_EQ(blkdeviotune.size_iops_sec,
> +             "blkdeviotune.size_iops_sec",
> +             true);
> +
> +    CHECK_EQ(transient, "transient", true);

Fields below are strings, but CHECK_EQ doesn't use string comparison.

> +    CHECK_EQ(serial, "serial", true);
> +    CHECK_EQ(wwn, "wwn", true);
> +    CHECK_EQ(vendor, "vendor", true);
> +    CHECK_EQ(product, "product", true);
> +
> +    CHECK_EQ(info.bootIndex, "boot order", true);
> +
> +    if (disk->info.alias && STRNEQ(disk->info.alias, orig_disk->info.alias)) {

The alias isn't parsed from the domain so this probably won't ever
trigger.

> +        virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
> +                       _("cannot modify field '%s' of the disk"),
> +                       "alias name");
> +        return false;
> +    }
> +
> +#undef CHECK_EQ
> +
> +    return true;
> +}
> +
>  int
>  virDomainDiskDefAssignAddress(virDomainXMLOptionPtr xmlopt,
>                                virDomainDiskDefPtr def)

Peter

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