Messages in this thread | | | Subject | Re: [PATCH net V2 4/4] vhost: log dirty page correctly | From | Jason Wang <> | Date | Thu, 13 Dec 2018 10:39:41 +0800 |
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On 2018/12/12 下午10:32, Michael S. Tsirkin wrote: > On Wed, Dec 12, 2018 at 06:08:19PM +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> > It's a nasty bug for sure but it's been like this for a long > time so I'm inclined to say let's put it in 4.21, > and queue for stable. > > So please split this out from this series.
Ok.
> > Also, I'd like to see a feature bit that allows GPA in IOTLBs.
Just to make sure I understand this. It looks to me we should:
- allow passing GIOVA->GPA through UAPI
- cache GIOVA->GPA somewhere but still use GIOVA->HVA in device IOTLB for performance
Is this what you suggest?
Thanks
> >> --- >> drivers/vhost/net.c | 3 +- >> drivers/vhost/vhost.c | 79 +++++++++++++++++++++++++++++++++++-------- >> drivers/vhost/vhost.h | 3 +- >> 3 files changed, 69 insertions(+), 16 deletions(-) >> >> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c >> index ad7a6f475a44..784df2b49628 100644 >> --- a/drivers/vhost/net.c >> +++ b/drivers/vhost/net.c >> @@ -1192,7 +1192,8 @@ 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 55e5aa662ad5..3660310604fd 100644 >> --- a/drivers/vhost/vhost.c >> +++ b/drivers/vhost/vhost.c >> @@ -1733,11 +1733,67 @@ 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) { >> + gpa = u->start + hva - u->userspace_addr; >> + r = log_write(vq->log_base, gpa, len); >> + if (r < 0) >> + return r; >> + hit = true; >> + } >> + } >> + >> + /* No reverse mapping, should be a bug */ >> + WARN_ON(!hit); > Maybe it should but userspace can trigger this easily I think. > We need to stop the device not warn in kernel log. > > Also there's an error fd: VHOST_SET_VRING_ERR, need to wake it up. >
Ok.
>> + return 0; >> +} >> + >> +static void log_used(struct vhost_virtqueue *vq, u64 used_offset, u64 len) >> +{ >> + struct iovec iov[64]; >> + int i, ret; >> + >> + if (!vq->iotlb) { >> + log_write(vq->log_base, vq->log_addr + used_offset, len); >> + return; >> + } > This change seems questionable. used ring writes > use their own machinery it does not go through iotlb. > Same should apply to log I think.
The problem is used ring may not be physically contiguous with Device IOTLB enabled. So it should go through it.
> >> + >> + ret = translate_desc(vq, (u64)(uintptr_t)vq->used + used_offset, >> + len, iov, 64, VHOST_ACCESS_WO); >> + WARN_ON(ret < 0); > > Same thing here. translation failures can be triggered from guest. > warn on is not a good error handling strategy ...
Ok. Let me fix it.
Thanks
>> + >> + for (i = 0; i < ret; i++) { >> + ret = log_write_hva(vq, (u64)(uintptr_t)iov[i].iov_base, >> + iov[i].iov_len); >> + WARN_ON(ret); >> + } >> +} >> + >> int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log, >> - unsigned int log_num, u64 len) >> + unsigned int log_num, u64 len, struct iovec *iov, int count) >> { >> int i, r; >> >> + if (vq->iotlb) { >> + for (i = 0; i < count; i++) { >> + r = log_write_hva(vq, (u64)(uintptr_t)iov[i].iov_base, >> + iov[i].iov_len); >> + if (r < 0) >> + return r; >> + } >> + return 0; >> + } >> + >> /* Make sure data written is seen before log. */ >> smp_wmb(); >> for (i = 0; i < log_num; ++i) { >> @@ -1769,9 +1825,8 @@ static int vhost_update_used_flags(struct vhost_virtqueue *vq) >> smp_wmb(); >> /* Log used flag write. */ >> used = &vq->used->flags; >> - log_write(vq->log_base, vq->log_addr + >> - (used - (void __user *)vq->used), >> - sizeof vq->used->flags); >> + log_used(vq, (used - (void __user *)vq->used), >> + sizeof vq->used->flags); >> if (vq->log_ctx) >> eventfd_signal(vq->log_ctx, 1); >> } >> @@ -1789,9 +1844,8 @@ static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event) >> smp_wmb(); >> /* Log avail event write */ >> used = vhost_avail_event(vq); >> - log_write(vq->log_base, vq->log_addr + >> - (used - (void __user *)vq->used), >> - sizeof *vhost_avail_event(vq)); >> + log_used(vq, (used - (void __user *)vq->used), >> + sizeof *vhost_avail_event(vq)); >> if (vq->log_ctx) >> eventfd_signal(vq->log_ctx, 1); >> } >> @@ -2191,10 +2245,8 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq, >> /* Make sure data is seen before log. */ >> smp_wmb(); >> /* Log used ring entry write. */ >> - log_write(vq->log_base, >> - vq->log_addr + >> - ((void __user *)used - (void __user *)vq->used), >> - count * sizeof *used); >> + log_used(vq, ((void __user *)used - (void __user *)vq->used), >> + count * sizeof *used); >> } >> old = vq->last_used_idx; >> new = (vq->last_used_idx += count); >> @@ -2236,9 +2288,8 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads, >> /* Make sure used idx is seen before log. */ >> smp_wmb(); >> /* Log used index update. */ >> - log_write(vq->log_base, >> - vq->log_addr + offsetof(struct vring_used, idx), >> - sizeof vq->used->idx); >> + log_used(vq, offsetof(struct vring_used, idx), >> + sizeof vq->used->idx); >> if (vq->log_ctx) >> eventfd_signal(vq->log_ctx, 1); >> } >> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h >> index 466ef7542291..1b675dad5e05 100644 >> --- a/drivers/vhost/vhost.h >> +++ b/drivers/vhost/vhost.h >> @@ -205,7 +205,8 @@ bool vhost_vq_avail_empty(struct vhost_dev *, struct vhost_virtqueue *); >> bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *); >> >> int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log, >> - unsigned int log_num, u64 len); >> + unsigned int log_num, u64 len, >> + struct iovec *iov, int count); >> int vq_iotlb_prefetch(struct vhost_virtqueue *vq); >> >> struct vhost_msg_node *vhost_new_msg(struct vhost_virtqueue *vq, int type); >> -- >> 2.17.1
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