Re: VM save/restore

[Junjie Wei <junjie.wei@oracle.com>]

On 08/18/2012 02:38 AM, Keir Fraser wrote:
>> It was caused by a hard-coded limit in tools/libxc/xc_domain_save.c:
>>
>> if ( info.max_vcpu_id >= 64 )
>> {
>>        ERROR("Too many VCPUS in guest!");
>>        goto out;
>> }
>>
>> And also in tools/libxc/xc_domain_restore.c:
>>
>> case XC_SAVE_ID_VCPU_INFO:
>>        buf->new_ctxt_format = 1;
>>        if ( RDEXACT(fd, &buf->max_vcpu_id, sizeof(buf->max_vcpu_id)) ||
>>            buf->max_vcpu_id >= 64 || RDEXACT(fd, &buf->vcpumap,
>>                                              sizeof(uint64_t)) ) {
>>            PERROR("Error when reading max_vcpu_id");
>>            return -1;
>>        }
>>
>> The code above is in both xen-4.1.2 and xen-unstable.
>>
>> I think if a VM can be successfully started, then save/restore should
>> also work. So I made a patch and did some testing.
>
> The check for 64 VCPUs is to cover the fact we only save/restore a 64-bit
> vcpumap. That would need fixing too surely, ot CPUs > 64 would be offline
> after restore I would imagine.
>
> And what is a PVM guest?
>
>   -- Keir
>

Paravirtualization / modified kernel. Am I using the wrong term "PVM"?

Thanks,
Junjie