Messages in this thread | | | Subject | Re: [PATCH net V2] vhost: log dirty page correctly | From | Jason Wang <> | Date | Fri, 11 Jan 2019 11:58:32 +0800 |
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On 2019/1/10 下午10:07, Michael S. Tsirkin wrote: > On Thu, Jan 10, 2019 at 08:37:17PM +0800, Jason Wang wrote: >> On 2019/1/9 下午10:25, Michael S. Tsirkin wrote: >>> On Wed, Jan 09, 2019 at 03:29:47PM +0800, Jason Wang wrote: >>>> Vhost dirty page logging API is designed to sync through GPA. But we >>>> try to log GIOVA when device IOTLB is enabled. This is wrong and may >>>> lead to missing data after migration. >>>> >>>> To solve this issue, when logging with device IOTLB enabled, we will: >>>> >>>> 1) reuse the device IOTLB translation result of GIOVA->HVA mapping to >>>> get HVA, for writable descriptor, get HVA through iovec. For used >>>> ring update, translate its GIOVA to HVA >>>> 2) traverse the GPA->HVA mapping to get the possible GPA and log >>>> through GPA. Pay attention this reverse mapping is not guaranteed >>>> to be unique, so we should log each possible GPA in this case. >>>> >>>> This fix the failure of scp to guest during migration. In -next, we >>>> will probably support passing GIOVA->GPA instead of GIOVA->HVA. >>>> >>>> Fixes: 6b1e6cc7855b ("vhost: new device IOTLB API") >>>> Reported-by: Jintack Lim<jintack@cs.columbia.edu> >>>> Cc: Jintack Lim<jintack@cs.columbia.edu> >>>> Signed-off-by: Jason Wang<jasowang@redhat.com> >>>> --- >>>> The patch is needed for stable. >>>> Changes from V1: >>>> - return error instead of warn >>>> --- >>>> drivers/vhost/net.c | 3 +- >>>> drivers/vhost/vhost.c | 82 +++++++++++++++++++++++++++++++++++-------- >>>> drivers/vhost/vhost.h | 3 +- >>>> 3 files changed, 72 insertions(+), 16 deletions(-) >>>> >>>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c >>>> index 36f3d0f49e60..bca86bf7189f 100644 >>>> --- a/drivers/vhost/net.c >>>> +++ b/drivers/vhost/net.c >>>> @@ -1236,7 +1236,8 @@ static void handle_rx(struct vhost_net *net) >>>> if (nvq->done_idx > VHOST_NET_BATCH) >>>> vhost_net_signal_used(nvq); >>>> if (unlikely(vq_log)) >>>> - vhost_log_write(vq, vq_log, log, vhost_len); >>>> + vhost_log_write(vq, vq_log, log, vhost_len, >>>> + vq->iov, in); >>>> total_len += vhost_len; >>>> if (unlikely(vhost_exceeds_weight(++recv_pkts, total_len))) { >>>> vhost_poll_queue(&vq->poll); >>>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c >>>> index 9f7942cbcbb2..ee095f08ffd4 100644 >>>> --- a/drivers/vhost/vhost.c >>>> +++ b/drivers/vhost/vhost.c >>>> @@ -1733,11 +1733,70 @@ static int log_write(void __user *log_base, >>>> return r; >>>> } >>>> +static int log_write_hva(struct vhost_virtqueue *vq, u64 hva, u64 len) >>>> +{ >>>> + struct vhost_umem *umem = vq->umem; >>>> + struct vhost_umem_node *u; >>>> + u64 gpa; >>>> + int r; >>>> + bool hit = false; >>>> + >>>> + list_for_each_entry(u, &umem->umem_list, link) { >>>> + if (u->userspace_addr < hva && >>>> + u->userspace_addr + u->size >= >>>> + hva + len) { >>> So this tries to see that the GPA range is completely within >>> the GVA region. Does this have to be the case? >> You mean e.g a buffer that crosses the boundary of two memory regions? > Yes - where hva and gva could be contigious.
Ok, let me add the overlap range logging in v3.
> > >>> And if yes why not return 0 below instead of hit = true? >> I think it's safe but not sure for the case like two GPAs can map to same >> HVA? > Oh I see. Yes that's possible. Document the motivation? >
Ok.
Thanks
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