Re: [PATCH 5/5] conf: Check for hostdev conflicts when assign default disk address

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On Mon, Jun 22, 2015 at 05:05:07PM -0400, John Ferlan wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1210587  (completed)
> 
> When generating the default drive address for a SCSI <disk> device,
> check the generated address to ensure it doesn't conflict with a SCSI
> <hostdev> address. The <disk> address generation algorithm uses the
> <target> "dev" name in order to determine which controller and unit
> in order to place the device. Since a SCSI <hostdev> device doesn't
> require a target device name, its placement on the guest SCSI address
> "could" conflict.  For instance, if a SCSI <hostdev> exists at
> controller=0 unit=0 and an attempt to hotplug 'sda' into the guest
> made, there would be a conflict if the <hostdev> is already using
> /dev/sda.
> 
> Signed-off-by: John Ferlan <jferlan@xxxxxxxxxx>
> ---
>  src/conf/domain_conf.c  | 40 +++++++++++++++++++++++++++++-----------
>  src/conf/domain_conf.h  |  3 ++-
>  src/qemu/qemu_command.c |  4 ++--
>  src/vmx/vmx.c           | 22 ++++++++++++----------
>  src/vmx/vmx.h           |  3 ++-
>  5 files changed, 47 insertions(+), 25 deletions(-)
> 
> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index 6259d4a..0999e86 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -5672,7 +5672,8 @@ virDomainDiskFindByBusAndDst(virDomainDefPtr def,
>  
>  int
>  virDomainDiskDefAssignAddress(virDomainXMLOptionPtr xmlopt,
> -                              virDomainDiskDefPtr def)
> +                              virDomainDiskDefPtr def,
> +                              const virDomainDef *vmdef)
>  {
>      int idx = virDiskNameToIndex(def->dst);
>      if (idx < 0) {
> @@ -5683,7 +5684,10 @@ virDomainDiskDefAssignAddress(virDomainXMLOptionPtr xmlopt,
>      }
>  
>      switch (def->bus) {
> -    case VIR_DOMAIN_DISK_BUS_SCSI:
> +    case VIR_DOMAIN_DISK_BUS_SCSI: {
> +        unsigned int controller;
> +        unsigned int unit;
> +
>          def->info.type = VIR_DOMAIN_DEVICE_ADDRESS_TYPE_DRIVE;
>  
>          if (xmlopt->config.hasWideSCSIBus) {
> @@ -5692,22 +5696,36 @@ virDomainDiskDefAssignAddress(virDomainXMLOptionPtr xmlopt,
>               * Unit 7 is the SCSI controller itself. Therefore unit 7
>               * cannot be assigned to disks and is skipped.
>               */
> -            def->info.addr.drive.controller = idx / 15;
> -            def->info.addr.drive.bus = 0;
> -            def->info.addr.drive.unit = idx % 15;
> +            controller = idx / 15;
> +            unit = idx % 15;
>  
>              /* Skip the SCSI controller at unit 7 */
> -            if (def->info.addr.drive.unit >= 7)
> -                ++def->info.addr.drive.unit;
> +            if (unit >= 7)
> +                ++unit;
>          } else {
>              /* For a narrow SCSI bus we define the default mapping to be
>               * 7 units per bus, 1 bus per controller, many controllers */
> -            def->info.addr.drive.controller = idx / 7;
> -            def->info.addr.drive.bus = 0;
> -            def->info.addr.drive.unit = idx % 7;
> +            controller = idx / 7;
> +            unit = idx % 7;
> +        }
> +

This mixes non-functional and functional changes.

> +        if (virDomainDriveAddressIsUsedByHostdev(vmdef,
> +                                                 VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_SCSI,
> +                                                 controller, 0, 0, unit)) {
> +            virReportError(VIR_ERR_XML_ERROR,
> +                           _("address generated using disk target name '%s' "
> +                             "may conflict with SCSI host device address "
> +                             "controller='%u' bus='%u' target='%u' unit='%u"),
> +                           def->dst, controller, 0, 0, unit);

'may conflict' sounds ambiguous. Either it does conflict and we should
reject it, or it does not and there is no error.

And this seems like a problem of libvirt's address generation algorithm,
not an XML error.

Jan

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