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Re: [libvirt] [PATCH v2 3/3] virQEMUDriverDomainABIStability: Check for memoryBacking



On 05/24/2017 05:06 PM, Daniel P. Berrange wrote:
> On Wed, May 24, 2017 at 04:45:57PM +0200, Michal Privoznik wrote:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1450349
>>
>> Problem is, qemu fails to load guest memory image if these
>> attribute change on migration/restore from an image.
> 
> [snip]
> 
>> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
>> index 35fd79de8..c1ff8ca8a 100644
>> --- a/src/qemu/qemu_domain.c
>> +++ b/src/qemu/qemu_domain.c
>> @@ -5797,6 +5797,46 @@ qemuDomainUpdateMemoryDeviceInfo(virQEMUDriverPtr driver,
>>  }
>>  
>>  
>> +static bool
>> +qemuDomainABIStabilityCheck(const virDomainDef *src,
>> +                            const virDomainDef *dst)
>> +{
>> +    if (src->mem.source != dst->mem.source) {
>> +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>> +                       _("Target memoryBacking source '%s' doesn't "
>> +                         "match source memoryBacking source'%s'"),
>> +                       virDomainMemorySourceTypeToString(dst->mem.source),
>> +                       virDomainMemorySourceTypeToString(src->mem.source));
>> +        return false;
>> +    }
>> +
>> +    if (src->mem.access != dst->mem.access) {
>> +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>> +                       _("Target memoryBacking access '%s' doesn't "
>> +                         "match access memoryBacking access'%s'"),
>> +                       virDomainMemoryAccessTypeToString(dst->mem.access),
>> +                       virDomainMemoryAccessTypeToString(src->mem.access));
>> +        return false;
>> +    }
>> +
>> +    if (src->mem.allocation != dst->mem.allocation) {
>> +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>> +                       _("Target memoryBacking allocation '%s' doesn't "
>> +                         "match allocation memoryBacking allocation'%s'"),
>> +                       virDomainMemoryAllocationTypeToString(dst->mem.allocation),
>> +                       virDomainMemoryAllocationTypeToString(src->mem.allocation));
>> +        return false;
>> +    }
> 
> 
> Do we really need to blacklist all of these changes. I can understand that
> changing the memory source would affect migration ABI, as it causes us to
> use the memory backend command line config differently.
> 
> Assuming that matches though, I'm sceptical that changing 'access' or
> 'allocation' affects ABI.

Yep, you're right. Only memory source change causes trouble. Other twos
can be changed without any harm. v2 on its way.

Michal


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