linux-kernel - Re: [PATCH] vhost: introduce vDPA based backend

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Date:   Wed, 5 Feb 2020 13:50:28 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Tiwei Bie <tiwei.bie@...el.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, shahafs@...lanox.com, jgg@...lanox.com,
        rob.miller@...adcom.com, haotian.wang@...ive.com,
        eperezma@...hat.com, lulu@...hat.com, parav@...lanox.com,
        rdunlap@...radead.org, hch@...radead.org, jiri@...lanox.com,
        hanand@...inx.com, mhabets@...arflare.com,
        maxime.coquelin@...hat.com, lingshan.zhu@...el.com,
        dan.daly@...el.com, cunming.liang@...el.com, zhihong.wang@...el.com
Subject: Re: [PATCH] vhost: introduce vDPA based backend


On 2020/2/5 下午1:31, Michael S. Tsirkin wrote:
> On Wed, Feb 05, 2020 at 11:12:21AM +0800, Jason Wang wrote:
>> On 2020/2/5 上午10:05, Tiwei Bie wrote:
>>> On Tue, Feb 04, 2020 at 02:46:16PM +0800, Jason Wang wrote:
>>>> On 2020/2/4 下午2:01, 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 interface?
>>>>>
>>>> Sure, so that basically VHOST_IOTLB_UPDATE/INVALIDATE I think?
>>> Do you mean we let userspace to only use VHOST_IOTLB_UPDATE/INVALIDATE
>>> 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->uaddr?
>>>
>>> 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 {
     __u64 iova;
     __u64 size;
     __u64 uaddr;
#define VHOST_ACCESS_RO      0x1
#define VHOST_ACCESS_WO      0x2
#define VHOST_ACCESS_RW      0x3
     __u8 perm;
#define VHOST_IOTLB_MISS           1
#define VHOST_IOTLB_UPDATE         2
#define VHOST_IOTLB_INVALIDATE     3
#define VHOST_IOTLB_ACCESS_FAIL    4
     __u8 type;
};

#define VHOST_IOTLB_MSG 0x1
#define VHOST_IOTLB_MSG_V2 0x2

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

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