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Subject: Re: [PATCH RFC 00/12] vdpa: generalize vdpa simulator and add block
 device
To:     Stefano Garzarella <sgarzare@redhat.com>,
        virtualization@lists.linux-foundation.org
Cc:     Stefan Hajnoczi <stefanha@redhat.com>,
        Laurent Vivier <lvivier@redhat.com>,
        linux-kernel@vger.kernel.org, Eli Cohen <elic@nvidia.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Max Gurtovoy <mgurtovoy@nvidia.com>
References: <20201113134712.69744-1-sgarzare@redhat.com>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <93f207c0-61e6-3696-f218-e7d7ea9a7c93@redhat.com>
Date:   Mon, 16 Nov 2020 11:37:48 +0800
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On 2020/11/13 下午9:47, Stefano Garzarella wrote:
> Thanks to Max that started this work!
> I took his patches, and extended the block simulator a bit.
>
> This series moves the network device simulator in a new module
> (vdpa_sim_net) and leaves the generic functions in the vdpa_sim core
> module, allowing the possibility to add new vDPA device simulators.
> Then we added a new vdpa_sim_blk module to simulate a block device.
>
> I'm not sure about patch 11 ("vringh: allow vringh_iov_xfer() to skip
> bytes when ptr is NULL"), maybe we can add a new functions instead of
> modify vringh_iov_xfer().
>
> As Max reported, I'm also seeing errors with vdpa_sim_blk related to
> iotlb and vringh when there is high load, these are some of the error
> messages I can see randomly:
>
>    vringh: Failed to access avail idx at 00000000e8deb2cc
>    vringh: Failed to read head: idx 6289 address 00000000e1ad1d50
>    vringh: Failed to get flags at 000000006635d7a3
>
>    virtio_vdpa vdpa0: vringh_iov_push_iotlb() error: -14 offset: 0x2840000 len: 0x20000
>    virtio_vdpa vdpa0: vringh_iov_pull_iotlb() error: -14 offset: 0x58ee000 len: 0x3000
>
> These errors should all be related to the fact that iotlb_translate()
> fails with -EINVAL, so it seems that we miss some mapping.


Is this only reproducible when there's multiple co-current accessing of 
IOTLB? If yes, it's probably a hint that some kind of synchronization is 
still missed somewhere.

It might be useful to log the dma_map/unmp in both virtio_ring and 
vringh to see who is missing the map.

Thanks


>
> I'll debug more carefully, in the meantime can you give a first review?
>
> Thanks,
> Stefano
>
> Max Gurtovoy (4):
>    vhost-vdpa: add support for vDPA blk devices
>    vdpa: split vdpasim to core and net modules
>    vdpa_sim: remove hard-coded virtq count
>    vdpa: add vdpa simulator for block device
>
> Stefano Garzarella (8):
>    vdpa_sim: remove the limit of IOTLB entries
>    vdpa_sim: add struct vdpasim_device to store device properties
>    vdpa_sim: move config management outside of the core
>    vdpa_sim: use kvmalloc to allocate vdpasim->buffer
>    vdpa_sim: make vdpasim->buffer size configurable
>    vdpa_sim: split vdpasim_virtqueue's iov field in riov and wiov
>    vringh: allow vringh_iov_xfer() to skip bytes when ptr is NULL
>    vdpa_sim_blk: implement ramdisk behaviour
>
>   drivers/vdpa/vdpa_sim/vdpa_sim.h     | 117 +++++++++++
>   drivers/vdpa/vdpa_sim/vdpa_sim.c     | 283 +++++----------------------
>   drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 251 ++++++++++++++++++++++++
>   drivers/vdpa/vdpa_sim/vdpa_sim_net.c | 172 ++++++++++++++++
>   drivers/vhost/vdpa.c                 |  11 +-
>   drivers/vhost/vringh.c               |  16 +-
>   drivers/vdpa/Kconfig                 |  16 +-
>   drivers/vdpa/vdpa_sim/Makefile       |   2 +
>   8 files changed, 628 insertions(+), 240 deletions(-)
>   create mode 100644 drivers/vdpa/vdpa_sim/vdpa_sim.h
>   create mode 100644 drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
>   create mode 100644 drivers/vdpa/vdpa_sim/vdpa_sim_net.c
>