Re: [PATCH Kernel v18 6/7] vfio iommu: Add migration capability to report supported features

From: Kirti Wankhede <kwankhede@nvidia.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: <cjia@nvidia.com>, <kevin.tian@intel.com>, <ziye.yang@intel.com>,
	<changpeng.liu@intel.com>, <yi.l.liu@intel.com>,
	<mlevitsk@redhat.com>, <eskultet@redhat.com>, <cohuck@redhat.com>,
	<dgilbert@redhat.com>, <jonathan.davies@nutanix.com>,
	<eauger@redhat.com>, <aik@ozlabs.ru>, <pasic@linux.ibm.com>,
	<felipe@nutanix.com>, <Zhengxiao.zx@Alibaba-inc.com>,
	<shuangtai.tst@alibaba-inc.com>, <Ken.Xue@amd.com>,
	<zhi.a.wang@intel.com>, <yan.y.zhao@intel.com>,
	<qemu-devel@nongnu.org>, <kvm@vger.kernel.org>
Subject: Re: [PATCH Kernel v18 6/7] vfio iommu: Add migration capability to report supported features
Date: Thu, 7 May 2020 11:07:26 +0530	[thread overview]
Message-ID: <79f1a586-52be-ab72-493a-3a3c5ae6e252@nvidia.com> (raw)
In-Reply-To: <20200506162738.6e08dbf2@w520.home>

On 5/7/2020 3:57 AM, Alex Williamson wrote:
> On Mon, 4 May 2020 21:28:58 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> 
>> Added migration capability in IOMMU info chain.
>> User application should check IOMMU info chain for migration capability
>> to use dirty page tracking feature provided by kernel module.
>>
>> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
>> ---
>>   drivers/vfio/vfio_iommu_type1.c | 15 +++++++++++++++
>>   include/uapi/linux/vfio.h       | 14 ++++++++++++++
>>   2 files changed, 29 insertions(+)
>>
>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>> index 8b27faf1ec38..b38d278d7bff 100644
>> --- a/drivers/vfio/vfio_iommu_type1.c
>> +++ b/drivers/vfio/vfio_iommu_type1.c
>> @@ -2378,6 +2378,17 @@ static int vfio_iommu_iova_build_caps(struct vfio_iommu *iommu,
>>   	return ret;
>>   }
>>   
>> +static int vfio_iommu_migration_build_caps(struct vfio_info_cap *caps)
>> +{
>> +	struct vfio_iommu_type1_info_cap_migration cap_mig;
>> +
>> +	cap_mig.header.id = VFIO_IOMMU_TYPE1_INFO_CAP_MIGRATION;
>> +	cap_mig.header.version = 1;
>> +	cap_mig.flags = VFIO_IOMMU_INFO_CAPS_MIGRATION_DIRTY_PAGE_TRACK;
>> +
>> +	return vfio_info_add_capability(caps, &cap_mig.header, sizeof(cap_mig));
>> +}
>> +
>>   static long vfio_iommu_type1_ioctl(void *iommu_data,
>>   				   unsigned int cmd, unsigned long arg)
>>   {
>> @@ -2427,6 +2438,10 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>>   		if (ret)
>>   			return ret;
>>   
>> +		ret = vfio_iommu_migration_build_caps(&caps);
>> +		if (ret)
>> +			return ret;
>> +
>>   		if (caps.size) {
>>   			info.flags |= VFIO_IOMMU_INFO_CAPS;
>>   
>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
>> index e3cbf8b78623..df9ce8aaafab 100644
>> --- a/include/uapi/linux/vfio.h
>> +++ b/include/uapi/linux/vfio.h
>> @@ -1013,6 +1013,20 @@ struct vfio_iommu_type1_info_cap_iova_range {
>>   	struct	vfio_iova_range iova_ranges[];
>>   };
>>   
>> +/*
>> + * The migration capability allows to report supported features for migration.
>> + *
>> + * The structures below define version 1 of this capability.
>> + */
>> +#define VFIO_IOMMU_TYPE1_INFO_CAP_MIGRATION  1
>> +
>> +struct vfio_iommu_type1_info_cap_migration {
>> +	struct	vfio_info_cap_header header;
>> +	__u32	flags;
>> +	/* supports dirty page tracking */
>> +#define VFIO_IOMMU_INFO_CAPS_MIGRATION_DIRTY_PAGE_TRACK	(1 << 0)
>> +};
>> +
> 
> What about exposing the maximum supported dirty bitmap size and the
> supported page sizes?  Thanks,
> 

How should user application use that?

Thanks,
Kirti

> Alex
> 
>>   #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
>>   
>>   /**
> 