Messages in this thread | | | Subject | Re: [PATCH net V3] vhost: log dirty page correctly | From | Jason Wang <> | Date | Tue, 15 Jan 2019 15:14:32 +0800 |
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On 2019/1/15 上午2:04, Michael S. Tsirkin wrote: > On Fri, Jan 11, 2019 at 12:00:36PM +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> >> --- >> Changes from V2: >> - check and log the case of range overlap >> - remove unnecessary u64 cast >> - use smp_wmb() for the case of device IOTLB as well >> Changes from V1: >> - return error instead of warn >> --- >> drivers/vhost/net.c | 3 +- >> drivers/vhost/vhost.c | 88 ++++++++++++++++++++++++++++++++++++------- >> drivers/vhost/vhost.h | 3 +- >> 3 files changed, 78 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..55a2e8f9f8ca 100644 >> --- a/drivers/vhost/vhost.c >> +++ b/drivers/vhost/vhost.c >> @@ -1733,13 +1733,78 @@ 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 start, end; >> + int r; >> + bool hit = false; >> + >> + /* More than one GPAs can be mapped into a single HVA. So >> + * iterate all possible umems here to be safe. >> + */ >> + list_for_each_entry(u, &umem->umem_list, link) { >> + if (u->userspace_addr > hva - 1 + len || >> + u->userspace_addr - 1 + u->size < hva) >> + continue; >> + start = max(u->userspace_addr, hva); >> + end = min(u->userspace_addr - 1 + u->size, hva - 1 + len); >> + r = log_write(vq->log_base, >> + u->start + start - u->userspace_addr, >> + end - start + 1); >> + if (r < 0) >> + return r; >> + hit = true; >> + } >> + >> + if (!hit) >> + return -EFAULT; >> + >> + return 0; >> +} >> + > I definitely like the simplicity. > > But there's one point left here: if len crosses a region boundary, > but doesn't all fall within a region, we don't consistently report -EFAULT. > > So I suspect we need to start by finding a region that contains hva. > If there are many of these - move right to the end of the > leftmost one and then repeat until we run out of len > or fail to find a region and exit with -EFAULT. >
Ok, will do it in V4.
Thanks
> >
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