Hello Roger,
        Thank you for the time and patience you devoted to reading my messages 
and e-mails. I really appreciate that.
        Depend on your reply, I submit those against current HEAD 
(origin/master).

1. 0001 patch: introduce suspend_cancel mechanism for frontend devices.
1.1 On a cancelled suspend, xen frontend devices need know their state is 
invariant.
1.2 On a cancelled suspend the vcpu_info location does not change (it's still 
in the per-cpu area registered by xen_hvm_cpu_init()). So do not call 
xen_hvm_init_shared_info_page()
which would make the kernel think its back in the shared info. With the wrong 
vcpu_info, events cannot be received and the domain will hang after a cancelled 
suspend.

I declare a global suspend_cancelled variable in xen/xenbus/xenbusvar.h and 
export that to all the frontends that need it. It should also be a bool type 
instead of int. I merge together with a _set_suspend_cancelled() function.

2. 0002 patch: a userspace application need wait until stop_all_proc has 
finished during live migration.
If there is a user process which maybe often reads and writes xenstore, the 
application has been suspended after stop_all_proc is called. It held 
xs.request_mutex lock but in the xctrl_suspend() function xs_write and 
xs_suspend will not obtain this lock. So the VM will hang. In order to prevent 
this from happening, this process need wait until stop_all_proc has finished 
during live migration.

3. 0003 patch: wrong order of device resume causes virtual machine to become 
unresponsive after live migration.
Because wrong order of device resume, VM will hang after live migration. attach 
the Xen PV timer to the nexus directly as it was done before.

        In my laboratory, FreeBSD VMs under no load and high load(cpu 80% and 
memory 80%) were alive after made the live migration back and forth 1000 times.
        I want to know what about these patch, Please let me know if you have 
any questions. Thanks!

-----邮件原件-----
发件人: freebsd xen [mailto:roger....@citrix.com] 
发送时间: 2017年1月6日 14:44
收件人: Liuyingdong <liuyingd...@huawei.com>
抄送: freebsd-xen@freebsd.org; Zhaojun (Euler) <zhao.zhao...@huawei.com>; Suoben 
<suo...@huawei.com>; Ouyangzhaowei (Charles) <ouyangzhao...@huawei.com>; 
chuzhaosong <chuzhaos...@huawei.com>; Wanglinkai <wanglin...@huawei.com>
主题: Re: [PATCH]netfront: need release all resources after adding and removing 
NICs time and again

On Thu, Dec 15, 2016 at 02:00:53AM +0000, Liuyingdong wrote:
> Hello Roger,
>       Thank you for the time and patience you devoted to reading my messages 
> and e-mails. I really appreciate that.
>       I can't use git send-email so I attach the patches directly. In the 
> 0001 patch I introduce suspend_cancel mechanism for frontend devices and in 
> the 0002 patch I release all resources after hot unplug NICs.
> 
>     Note: These two patches is on the base of the origin/release/10.2.0 
> branch and the 0002 patch is made after the 0001 patch.

Hello,

Thanks for the patches, now they look fine. You will however need to submit 
those against current HEAD (origin/master), and then I will do the backport to
stable/10 and stable/11. I cannot apply a patch directly to stable branches 
without it being in HEAD first unless there's a good reason for it.

Replying to both patches here inline.

---8<---
> From fc85ac7eba55a5f14f5f7d81f0e1fc7fbf6a7447 Mon Sep 17 00:00:00 2001
> From: Yingdong Liu <liuyingd...@huawei.com>
> Date: Tue, 13 Dec 2016 21:53:25 +0800
> Subject: [PATCH] introduce suspend cancel mechanism for frontend 
> devices
> 

Can you elaborate a little bit more on the commit message here? What issues are 
you seeing without this patch applied? What is the result after applying the 
patch?

Commit messages are very important in order to know why a change is needed, 
specially when you look at them in for example 3 years time.

> ---
>  sys/dev/xen/blkfront/blkfront.c | 13 +++++++++++
>  sys/dev/xen/control/control.c   |  9 ++++++-
>  sys/dev/xen/netfront/netfront.c | 52 
> ++++++++++++++++++++++++++++++-----------
>  sys/x86/xen/hvm.c               | 16 ++++++++-----
>  sys/xen/xenbus/xenbusb.c        | 45 ++++++++++++++++++++++-------------
>  sys/xen/xenbus/xenbusvar.h      |  4 ++++
>  6 files changed, 102 insertions(+), 37 deletions(-)
> 
> diff --git a/sys/dev/xen/blkfront/blkfront.c 
> b/sys/dev/xen/blkfront/blkfront.c index a71251d..8d7c32a 100644
> --- a/sys/dev/xen/blkfront/blkfront.c
> +++ b/sys/dev/xen/blkfront/blkfront.c
> @@ -68,6 +68,8 @@ __FBSDID("$FreeBSD$");
>  
>  #include "xenbus_if.h"
>  
> +static int blkfront_suspend_cancelled = 0;

I see that you add one of those to each frontend you add cancel suspend 
support, together with a *_set_suspend_cancel function. Wouldn't it be easier 
to declare a global suspend_cancelled variable in xen/control.c and export that 
to all the frontends that need it? It should also be a bool type instead of int.

You can clear that variable after DEVICE_RESUME has finished.

>  /*--------------------------- Forward Declarations 
> ---------------------------*/  static void xbd_closing(device_t);  
> static void xbd_startio(struct xbd_softc *sc); @@ -1417,10 +1419,21 @@ 
> xbd_suspend(device_t dev)
>       return (retval);
>  }
>  
> +void xbd_set_suspend_cancel(void)
> +{
> +     blkfront_suspend_cancelled = 1;
> +}
> +
>  static int
>  xbd_resume(device_t dev)
>  {
>       struct xbd_softc *sc = device_get_softc(dev);
> +     

Stray tab.

> +     if(blkfront_suspend_cancelled == 1) {
          ^ missing space between "if" and "(".

> +             sc->xbd_state = XBD_STATE_CONNECTED;
> +             blkfront_suspend_cancelled = 0;
> +             return (0);
> +     }
>  
>       DPRINTK("xbd_resume: %s\n", xenbus_get_node(dev));
>  
> diff --git a/sys/dev/xen/control/control.c 
> b/sys/dev/xen/control/control.c index bc0609d..b500100 100644
> --- a/sys/dev/xen/control/control.c
> +++ b/sys/dev/xen/control/control.c
> @@ -400,7 +400,9 @@ xctrl_suspend()
>       /*
>        * Reset grant table info.
>        */
> -     gnttab_resume();
> +     if(suspend_cancelled == 0) {
          ^ missing space.

> +             gnttab_resume();
> +     }
>  
>  #ifdef SMP
>       if (smp_started && !CPU_EMPTY(&cpu_suspend_map)) { @@ -416,6 +418,11 
> @@ xctrl_suspend()
>        * FreeBSD really needs to add DEVICE_SUSPEND_CANCEL or
>        * similar.
>        */
> +     if(suspend_cancelled == 1) {
> +             xenbusb_set_suspend_cancel();
> +             xbd_set_suspend_cancel();
> +             xn_set_suspend_cancel();
> +     }

If you make suspend_cancelled global you wouldn't need to call all of those 
functions.

>       mtx_lock(&Giant);
>       DEVICE_RESUME(root_bus);
>       mtx_unlock(&Giant);
> diff --git a/sys/dev/xen/netfront/netfront.c 
> b/sys/dev/xen/netfront/netfront.c index d89c0e0..0caaa2c 100644
> --- a/sys/dev/xen/netfront/netfront.c
> +++ b/sys/dev/xen/netfront/netfront.c
> @@ -98,6 +98,8 @@ __FBSDID("$FreeBSD$");  #define NET_TX_RING_SIZE 
> __RING_SIZE((netif_tx_sring_t *)0, PAGE_SIZE)  #define 
> NET_RX_RING_SIZE __RING_SIZE((netif_rx_sring_t *)0, PAGE_SIZE)
>  
> +static int netfront_suspend_cancelled = 0;
> +
>  #if __FreeBSD_version >= 700000
>  /*
>   * Should the driver do LRO on the RX end @@ -192,6 +194,10 @@ static 
> int xennet_get_responses(struct netfront_info *np,
>       struct netfront_rx_info *rinfo, RING_IDX rp, RING_IDX *cons,
>       struct mbuf **list, int *pages_flipped_p);
>  
> +#ifdef INET
> +static void netfront_send_fake_arp(device_t dev, struct netfront_info 
> +*info); #endif
> +
>  #define virt_to_mfn(x) (vtomach(x) >> PAGE_SHIFT)
>  
>  #define INVALID_P2M_ENTRY (~0UL)
> @@ -493,6 +499,11 @@ netfront_suspend(device_t dev)
>       return (0);
>  }
>  
> +void xn_set_suspend_cancel(void)
> +{
> +     netfront_suspend_cancelled = 1;
> +}
> +
>  /**
>   * We are reconnecting to the backend, due to a suspend/resume, or a backend
>   * driver restart.  We tear down our netif structure and recreate it, 
> but @@ -504,6 +515,19 @@ netfront_resume(device_t dev)  {
>       struct netfront_info *info = device_get_softc(dev);
>  
> +     if(netfront_suspend_cancelled == 1) {
> +             info->xn_resume = true;
> +             XN_RX_LOCK(info);
> +             XN_TX_LOCK(info);
> +             netfront_carrier_on(info);
> +             XN_TX_UNLOCK(info);
> +             XN_RX_UNLOCK(info);
> +#ifdef INET
> +             netfront_send_fake_arp(dev, info);
> +#endif

I don't think you need to send an ARP on a cancelled suspend, the bridge should 
already have the mac address of the virtual interface in it's cache right?

> +             netfront_suspend_cancelled = 0;
> +             return (0);
> +     }
>       info->xn_resume = true;
>       netif_disconnect_backend(info);
>       return (0);
> @@ -2108,26 +2132,26 @@ create_netdev(device_t dev)
>       
>       /* Set up ifnet structure */
>       ifp = np->xn_ifp = if_alloc(IFT_ETHER);
> -     ifp->if_softc = np;
> -     if_initname(ifp, "xn",  device_get_unit(dev));
> -     ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
> -     ifp->if_ioctl = xn_ioctl;
> -     ifp->if_output = ether_output;
> -     ifp->if_start = xn_start;
> +     ifp->if_softc = np;
> +     if_initname(ifp, "xn",  device_get_unit(dev));
> +     ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
> +     ifp->if_ioctl = xn_ioctl;
> +     ifp->if_output = ether_output;
> +     ifp->if_start = xn_start;
>  #ifdef notyet
> -     ifp->if_watchdog = xn_watchdog;
> +     ifp->if_watchdog = xn_watchdog;
>  #endif
> -     ifp->if_init = xn_ifinit;
> -     ifp->if_snd.ifq_maxlen = NET_TX_RING_SIZE - 1;
> -     
> -     ifp->if_hwassist = XN_CSUM_FEATURES;
> -     ifp->if_capabilities = IFCAP_HWCSUM;
> +     ifp->if_init = xn_ifinit;
> +     ifp->if_snd.ifq_maxlen = NET_TX_RING_SIZE - 1;
> +
> +     ifp->if_hwassist = XN_CSUM_FEATURES;
> +     ifp->if_capabilities = IFCAP_HWCSUM;
>       ifp->if_hw_tsomax = 65536 - (ETHER_HDR_LEN + ETHER_VLAN_ENCAP_LEN);
>       ifp->if_hw_tsomaxsegcount = MAX_TX_REQ_FRAGS;
>       ifp->if_hw_tsomaxsegsize = PAGE_SIZE;
>       
> -     ether_ifattach(ifp, np->mac);
> -     callout_init(&np->xn_stat_ch, CALLOUT_MPSAFE);
> +     ether_ifattach(ifp, np->mac);
> +     callout_init(&np->xn_stat_ch, CALLOUT_MPSAFE);
>       netfront_carrier_off(np);

This chunk seems completely unrelated to the patch itself, is this some kind of 
code formatting cleanup? If so, this should be sent in a separate patch.

>       return (0);
> diff --git a/sys/x86/xen/hvm.c b/sys/x86/xen/hvm.c index 
> c386953..1c2ba9d 100644
> --- a/sys/x86/xen/hvm.c
> +++ b/sys/x86/xen/hvm.c
> @@ -517,10 +517,9 @@ xen_hvm_init(enum xen_hvm_init_type init_type)
>       int error;
>       int i;
>  
> -     if (init_type == XEN_HVM_INIT_CANCELLED_SUSPEND)
> -             return;
> -
> -     error = xen_hvm_init_hypercall_stubs();
> +     if (init_type != XEN_HVM_INIT_CANCELLED_SUSPEND) {
> +             error = xen_hvm_init_hypercall_stubs();
> +     }
>  
>       switch (init_type) {
>       case XEN_HVM_INIT_COLD:
> @@ -541,13 +540,17 @@ xen_hvm_init(enum xen_hvm_init_type init_type)
>               CPU_FOREACH(i)
>                       DPCPU_ID_SET(i, vcpu_info, NULL);
>               break;
> +     case XEN_HVM_INIT_CANCELLED_SUSPEND:
> +             break;
>       default:
>               panic("Unsupported HVM initialization type");
>       }
>  
>       xen_vector_callback_enabled = 0;
>       xen_domain_type = XEN_HVM_DOMAIN;
> -     xen_hvm_init_shared_info_page();
> +     if (init_type != XEN_HVM_INIT_CANCELLED_SUSPEND) {
> +             xen_hvm_init_shared_info_page();
> +     }
>       xen_hvm_set_callback(NULL);
>       xen_hvm_disable_emulated_devices();

I'm not sure I follow why this change to xen_hvm_init is needed, on a cancelled 
suspend you shouldn't need to re-set the callback vector or unplug any emulated 
devices.

>  }
> @@ -565,7 +568,8 @@ xen_hvm_resume(bool suspend_cancelled)
>           XEN_HVM_INIT_CANCELLED_SUSPEND : XEN_HVM_INIT_RESUME);
>  
>       /* Register vcpu_info area for CPU#0. */
> -     xen_hvm_cpu_init();
> +     if(!suspend_cancelled)
> +             xen_hvm_cpu_init();
>  }

Seeing this here, why don't we just avoid calling xen_hvm_resume from 
xctrl_suspend on a cancelled suspend?

>  static void
> diff --git a/sys/xen/xenbus/xenbusb.c b/sys/xen/xenbus/xenbusb.c index 
> 1f84795..cce83cd 100644
> --- a/sys/xen/xenbus/xenbusb.c
> +++ b/sys/xen/xenbus/xenbusb.c
> @@ -75,6 +75,8 @@ __FBSDID("$FreeBSD$");  #include 
> <xen/xenbus/xenbusb.h>  #include <xen/xenbus/xenbusvar.h>
>  
> +static int xenbusb_suspend_cancelled = 0;
> +
>  /*------------------------- Private Functions 
> --------------------------------*/
>  /**
>   * \brief Deallocate XenBus device instance variables.
> @@ -776,6 +778,11 @@ xenbusb_attach(device_t dev, char *bus_node, u_int 
> id_components)
>       return (0);
>  }
>  
> +void xenbusb_set_suspend_cancel(void) {
> +     xenbusb_suspend_cancelled = 1;
> +}
> +
>  int
>  xenbusb_resume(device_t dev)
>  {
> @@ -793,29 +800,32 @@ xenbusb_resume(device_t dev)
>                       if (device_get_state(kids[i]) == DS_NOTPRESENT)
>                               continue;
>  
> -                     ivars = device_get_ivars(kids[i]);
> +                     if(xenbusb_suspend_cancelled == 0) {
> +                             ivars = device_get_ivars(kids[i]);
>  
> -                     xs_unregister_watch(&ivars->xd_otherend_watch);
> -                     xenbus_set_state(kids[i], XenbusStateInitialising);
> +                             xs_unregister_watch(&ivars->xd_otherend_watch);
> +                             xenbus_set_state(kids[i], 
> XenbusStateInitialising);
>  
> -                     /*
> -                      * Find the new backend details and
> -                      * re-register our watch.
> -                      */
> -                     error = XENBUSB_GET_OTHEREND_NODE(dev, ivars);
> -                     if (error)
> -                             return (error);
> +                             /*
> +                              * Find the new backend details and
> +                              * re-register our watch.
> +                              */
> +                             error = XENBUSB_GET_OTHEREND_NODE(dev, ivars);
> +                             if (error)
> +                                     return (error);
>  
> -                     statepath = malloc(ivars->xd_otherend_path_len
> -                         + strlen("/state") + 1, M_XENBUS, M_WAITOK);
> -                     sprintf(statepath, "%s/state", ivars->xd_otherend_path);
> +                             statepath = malloc(ivars->xd_otherend_path_len
> +                                 + strlen("/state") + 1, M_XENBUS, M_WAITOK);
> +                             sprintf(statepath, "%s/state", 
> ivars->xd_otherend_path);
>  
> -                     free(ivars->xd_otherend_watch.node, M_XENBUS);
> -                     ivars->xd_otherend_watch.node = statepath;
> +                             free(ivars->xd_otherend_watch.node, M_XENBUS);
> +                             ivars->xd_otherend_watch.node = statepath;
> +                     }
>  
>                       DEVICE_RESUME(kids[i]);
>  
> -                     xs_register_watch(&ivars->xd_otherend_watch);
> +                     if(xenbusb_suspend_cancelled == 0)
> +                             xs_register_watch(&ivars->xd_otherend_watch);

Why don't you just add:

if (xenbusb_suspend_cancelled == 1) {
        DEVICE_RESUME(kids[i]);
        continue;
}

To the top of the loop? This would present adding a bunch of nested 
conditionals.

>  #if 0
>                       /*
>                        * Can't do this yet since we are running in @@ -834,6 
> +844,9 @@ 
> xenbusb_resume(device_t dev)
>               free(kids, M_TEMP);
>       }
>  
> +     if(xenbusb_suspend_cancelled == 1)
> +             xenbusb_suspend_cancelled = 0;
> +     
>       return (0);
>  }
>  
> diff --git a/sys/xen/xenbus/xenbusvar.h b/sys/xen/xenbus/xenbusvar.h 
> index ab5d01f..aff3b60 100644
> --- a/sys/xen/xenbus/xenbusvar.h
> +++ b/sys/xen/xenbus/xenbusvar.h
> @@ -272,4 +272,8 @@ void xenbus_localend_changed(device_t dev, const 
> char *path);
>  
>  #include "xenbus_if.h"
>  
> +void xenbusb_set_suspend_cancel(void); void 
> +xbd_set_suspend_cancel(void); void xn_set_suspend_cancel(void);
> +
>  #endif /* _XEN_XENBUS_XENBUSVAR_H */
> --
> 1.8.3.4
>
> From 423a959a268b205c048489e6addeba5db449e322 Mon Sep 17 00:00:00 2001
> From: Yingdong Liu <liuyingd...@huawei.com>
> Date: Thu, 15 Dec 2016 09:09:16 +0800
> Subject: [PATCH] [PATCH]netfront: need release all resources after 
> adding and  removing NICs time and again
> 
> ---
>  sys/dev/xen/netfront/netfront.c | 46 
> +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 46 insertions(+)
> 
> diff --git a/sys/dev/xen/netfront/netfront.c 
> b/sys/dev/xen/netfront/netfront.c index 0caaa2c..5b67e12 100644
> --- a/sys/dev/xen/netfront/netfront.c
> +++ b/sys/dev/xen/netfront/netfront.c
> @@ -2196,6 +2196,46 @@ netfront_detach(device_t dev)  }
>  
>  static void
> +netif_release_rx_bufs_copy(struct netfront_info *np) {
> +     struct mbuf *m;
> +     int i, ref;
> +     int busy = 0, inuse = 0;
> +
> +     XN_RX_LOCK(np);
> +
> +     for (i = 0; i < NET_RX_RING_SIZE; i++) {
> +             ref = np->grant_rx_ref[i];
> +
> +             if (ref == GRANT_REF_INVALID)
> +                     continue;
> +
> +             inuse++;
> +
> +             m = np->rx_mbufs[i];
> +
> +             if (!gnttab_end_foreign_access_ref(ref))
> +             {
> +                     busy++;
> +                     continue;
> +             }
> +
> +             gnttab_release_grant_reference(&np->gref_rx_head, ref);
> +             np->grant_rx_ref[i] = GRANT_REF_INVALID;
> +             add_id_to_freelist(np->rx_mbufs, i);
> +
> +             m_freem(m);
> +     }
> +
> +     if (busy)
> +             device_printf(np->xbdev, "Unable to release %d of %d "
> +                     "inuse grant references out of %ld total.\n",
> +                     busy, inuse, NET_RX_RING_SIZE);
> +     

Stray tab.

> +     XN_RX_UNLOCK(np);
> +}
> +
> +static void
>  netif_free(struct netfront_info *info)  {
>       XN_LOCK(info);
> @@ -2209,6 +2249,12 @@ netif_free(struct netfront_info *info)
>               info->xn_ifp = NULL;
>       }
>       ifmedia_removeall(&info->sc_media);
> +     netif_release_tx_bufs(info);
> +     if (info->copying_receiver)
> +             netif_release_rx_bufs_copy(info);
> +
> +     gnttab_free_grant_references(info->gref_tx_head);
> +     gnttab_free_grant_references(info->gref_rx_head);
>  }

This patch looks fine, but it needs to be rebased on top of HEAD in order to be 
applied.

Roger.

Attachment: 0001-introduce suspend_cancel mechanism for frontend devices.patch
Description: 0001-introduce suspend_cancel mechanism for frontend devices.patch

Attachment: 0002-a userspace application need wait until stop_all_proc has finished during live migration.patch
Description: 0002-a userspace application need wait until stop_all_proc has finished during live migration.patch

Attachment: 0003-wrong order of device resume causes virtual machine to become unresponsive after live migration.patch
Description: 0003-wrong order of device resume causes virtual machine to become unresponsive after live migration.patch

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