RE: [PATCH rfcv2 18/18] intel_iommu: Block migration if cap is updated

[Duan, Zhenzhong]

>-----Original Message-----
>From: Joao Martins <joao.m.martins@oracle.com>
>Subject: Re: [PATCH rfcv2 18/18] intel_iommu: Block migration if cap is
>updated
>
>On 01/02/2024 07:28, Zhenzhong Duan wrote:
>> When there is VFIO device and vIOMMU cap/ecap is updated based on
>host
>> IOMMU cap/ecap, migration should be blocked.
>>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>
>Is this really needed considering migration with vIOMMU is already blocked
>anyways?

VFIO device can be hot unplugged, then blocker due to vIOMMU is removed,
but we still need a blocker for cap/ecap update.

Thanks
Zhenzhong

>
>> ---
>>  hw/i386/intel_iommu.c | 16 ++++++++++++++--
>>  1 file changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
>> index 72cc8b2c71..7f9ff653b2 100644
>> --- a/hw/i386/intel_iommu.c
>> +++ b/hw/i386/intel_iommu.c
>> @@ -39,6 +39,7 @@
>>  #include "hw/i386/apic_internal.h"
>>  #include "kvm/kvm_i386.h"
>>  #include "migration/vmstate.h"
>> +#include "migration/blocker.h"
>>  #include "trace.h"
>>
>>  #define S_AW_BITS (VTD_MGAW_FROM_CAP(s->cap) + 1)
>> @@ -3829,6 +3830,8 @@ static int
>vtd_check_legacy_hdev(IntelIOMMUState *s,
>>      return 0;
>>  }
>>
>> +static Error *vtd_mig_blocker;
>> +
>>  static int vtd_check_iommufd_hdev(IntelIOMMUState *s,
>>                                    IOMMUFDDevice *idev,
>>                                    Error **errp)
>> @@ -3860,8 +3863,17 @@ static int
>vtd_check_iommufd_hdev(IntelIOMMUState *s,
>>          tmp_cap |= VTD_CAP_MGAW(host_mgaw + 1);
>>      }
>>
>> -    s->cap = tmp_cap;
>> -    return 0;
>> +    if (s->cap != tmp_cap) {
>> +        if (vtd_mig_blocker == NULL) {
>> +            error_setg(&vtd_mig_blocker,
>> +                       "cap/ecap update from host IOMMU block migration");
>> +            ret = migrate_add_blocker(&vtd_mig_blocker, errp);
>> +        }
>> +        if (!ret) {
>> +            s->cap = tmp_cap;
>> +        }
>> +    }
>> +    return ret;
>>  }
>>
>>  static int vtd_check_hdev(IntelIOMMUState *s, VTDHostIOMMUDevice
>*vtd_hdev,