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Subject: Re: [PATCH] vhost: introduce vDPA based backend
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Tiwei Bie <tiwei.bie@intel.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, shahafs@mellanox.com, jgg@mellanox.com,
        rob.miller@broadcom.com, haotian.wang@sifive.com,
        eperezma@redhat.com, lulu@redhat.com, parav@mellanox.com,
        rdunlap@infradead.org, hch@infradead.org, jiri@mellanox.com,
        hanand@xilinx.com, mhabets@solarflare.com,
        maxime.coquelin@redhat.com, lingshan.zhu@intel.com,
        dan.daly@intel.com, cunming.liang@intel.com, zhihong.wang@intel.com
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From:   Jason Wang <jasowang@redhat.com>
Message-ID: <eb53d1c2-92ae-febf-f502-2d3e107ee608@redhat.com>
Date:   Wed, 5 Feb 2020 13:50:28 +0800
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On 2020/2/5 =E4=B8=8B=E5=8D=881:31, Michael S. Tsirkin wrote:
> On Wed, Feb 05, 2020 at 11:12:21AM +0800, Jason Wang wrote:
>> On 2020/2/5 =E4=B8=8A=E5=8D=8810:05, Tiwei Bie wrote:
>>> On Tue, Feb 04, 2020 at 02:46:16PM +0800, Jason Wang wrote:
>>>> On 2020/2/4 =E4=B8=8B=E5=8D=882:01, Michael S. Tsirkin wrote:
>>>>> On Tue, Feb 04, 2020 at 11:30:11AM +0800, Jason Wang wrote:
>>>>>> 5) generate diffs of memory table and using IOMMU API to setup the=
 dma
>>>>>> mapping in this method
>>>>> Frankly I think that's a bunch of work. Why not a MAP/UNMAP interfa=
ce?
>>>>>
>>>> Sure, so that basically VHOST_IOTLB_UPDATE/INVALIDATE I think?
>>> Do you mean we let userspace to only use VHOST_IOTLB_UPDATE/INVALIDAT=
E
>>> to do the DMA mapping in vhost-vdpa case? When vIOMMU isn't available=
,
>>> userspace will set msg->iova to GPA, otherwise userspace will set
>>> msg->iova to GIOVA, and vhost-vdpa module will get HPA from msg->uadd=
r?
>>>
>>> Thanks,
>>> Tiwei
>> I think so. Michael, do you think this makes sense?
>>
>> Thanks
> to make sure, could you post the suggested argument format for
> these ioctls?
>

It's the existed uapi:

/* no alignment requirement */
struct vhost_iotlb_msg {
 =C2=A0=C2=A0=C2=A0 __u64 iova;
 =C2=A0=C2=A0=C2=A0 __u64 size;
 =C2=A0=C2=A0=C2=A0 __u64 uaddr;
#define VHOST_ACCESS_RO=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0x1
#define VHOST_ACCESS_WO=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0x2
#define VHOST_ACCESS_RW=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0x3
 =C2=A0=C2=A0=C2=A0 __u8 perm;
#define VHOST_IOTLB_MISS=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0 1
#define VHOST_IOTLB_UPDATE=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
 2
#define VHOST_IOTLB_INVALIDATE=C2=A0=C2=A0=C2=A0=C2=A0 3
#define VHOST_IOTLB_ACCESS_FAIL=C2=A0=C2=A0=C2=A0 4
 =C2=A0=C2=A0=C2=A0 __u8 type;
};

#define VHOST_IOTLB_MSG 0x1
#define VHOST_IOTLB_MSG_V2 0x2

struct vhost_msg {
 =C2=A0=C2=A0=C2=A0 int type;
 =C2=A0=C2=A0=C2=A0 union {
 =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 struct vhost_iotlb_msg iotlb;
 =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 __u8 padding[64];
 =C2=A0=C2=A0=C2=A0 };
};

struct vhost_msg_v2 {
 =C2=A0=C2=A0=C2=A0 __u32 type;
 =C2=A0=C2=A0=C2=A0 __u32 reserved;
 =C2=A0=C2=A0=C2=A0 union {
 =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 struct vhost_iotlb_msg iotlb;
 =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 __u8 padding[64];
 =C2=A0=C2=A0=C2=A0 };
};