| Message ID | 1513327555-17520-3-git-send-email-jianjay.zhou@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, 15 Dec 2017 16:45:55 +0800 Jay Zhou <jianjay.zhou@huawei.com> wrote: > If the VM already has N(N>8) available memory slots for vhost user, > the VM will be crashed in vhost_user_set_mem_table if we try to > hotplug the first vhost user NIC. > This patch checks if memslots number exceeded or not after updating > vhost_user_used_memslots. Can't understand commit message, pls rephrase (what is being fixed, and how it's fixed) also include reproducing steps for crash and maybe describe call flow/backtrace that triggers crash. PS: I wasn't able to reproduce crash > > Signed-off-by: Jay Zhou <jianjay.zhou@huawei.com> > --- > hw/virtio/vhost.c | 27 +++++++++++++++++++++++---- > 1 file changed, 23 insertions(+), 4 deletions(-) > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > index 59a32e9..e45f5e2 100644 > --- a/hw/virtio/vhost.c > +++ b/hw/virtio/vhost.c > @@ -1234,6 +1234,18 @@ static void vhost_virtqueue_cleanup(struct vhost_virtqueue *vq) > event_notifier_cleanup(&vq->masked_notifier); > } > > +static bool vhost_dev_used_memslots_is_exceeded(struct vhost_dev *hdev) > +{ > + if (hdev->vhost_ops->vhost_get_used_memslots() > > + hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > + error_report("vhost backend memory slots limit is less" > + " than current number of present memory slots"); > + return true; > + } > + > + return false; > +} > + > int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > VhostBackendType backend_type, uint32_t busyloop_timeout) > { > @@ -1252,10 +1264,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > goto fail; > } > > - if (hdev->vhost_ops->vhost_get_used_memslots() > > - hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > - error_report("vhost backend memory slots limit is less" > - " than current number of present memory slots"); > + if (vhost_dev_used_memslots_is_exceeded(hdev)) { why do you keep this check? it seems always be false > r = -1; > goto fail; > } > @@ -1341,6 +1350,16 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > hdev->memory_changed = false; > memory_listener_register(&hdev->memory_listener, &address_space_memory); > QLIST_INSERT_HEAD(&vhost_devices, hdev, entry); > + > + if (vhost_dev_used_memslots_is_exceeded(hdev)) { > + r = -1; > + if (busyloop_timeout) { > + goto fail_busyloop; > + } else { > + goto fail; > + } > + } seem to be right thing to do, since after registering listener for the first time used_memslots will be updated to actual value. I did some testing and without this hunk/patch on 'device_add virtio-net-pci,netdev=net0' qemu prints: qemu-system-x86_64: vhost_set_mem_table failed: Argument list too long (7) qemu-system-x86_64: unable to start vhost net: 7: falling back on userspace virtio and network is operational in guest, but with this patch "netdev_add ...,vhost-on" prints: vhost backend memory slots limit is less than current number of present memory slots vhost-net requested but could not be initialized and following "device_add virtio-net-pci,netdev=net0" prints: TUNSETOFFLOAD ioctl() failed: Bad file descriptor TUNSETOFFLOAD ioctl() failed: Bad file descriptor adapter is still hot-plugged but guest networking is broken (can't get IP address via DHCP) so patch seems introduces a regression or something broken elsewhere and this exposes issue, not sure what qemu reaction should be in this case i.e. when netdev_add fails 1: should we fail followed up device_add or 2: make it fall back to userspace virtio I'd go for #2, Michael what's your take on it? > + > return 0; > > fail_busyloop:
On Fri, Dec 22, 2017 at 07:48:55PM +0100, Igor Mammedov wrote: > On Fri, 15 Dec 2017 16:45:55 +0800 > Jay Zhou <jianjay.zhou@huawei.com> wrote: > > > If the VM already has N(N>8) available memory slots for vhost user, > > the VM will be crashed in vhost_user_set_mem_table if we try to > > hotplug the first vhost user NIC. > > This patch checks if memslots number exceeded or not after updating > > vhost_user_used_memslots. > Can't understand commit message, pls rephrase (what is being fixed, and how it's fixed) > also include reproducing steps for crash and maybe describe call flow/backtrace > that triggers crash. > > PS: > I wasn't able to reproduce crash > > > > > Signed-off-by: Jay Zhou <jianjay.zhou@huawei.com> > > --- > > hw/virtio/vhost.c | 27 +++++++++++++++++++++++---- > > 1 file changed, 23 insertions(+), 4 deletions(-) > > > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > > index 59a32e9..e45f5e2 100644 > > --- a/hw/virtio/vhost.c > > +++ b/hw/virtio/vhost.c > > @@ -1234,6 +1234,18 @@ static void vhost_virtqueue_cleanup(struct vhost_virtqueue *vq) > > event_notifier_cleanup(&vq->masked_notifier); > > } > > > > +static bool vhost_dev_used_memslots_is_exceeded(struct vhost_dev *hdev) > > +{ > > + if (hdev->vhost_ops->vhost_get_used_memslots() > > > + hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > > + error_report("vhost backend memory slots limit is less" > > + " than current number of present memory slots"); > > + return true; > > + } > > + > > + return false; > > +} > > + > > int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > > VhostBackendType backend_type, uint32_t busyloop_timeout) > > { > > @@ -1252,10 +1264,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > > goto fail; > > } > > > > - if (hdev->vhost_ops->vhost_get_used_memslots() > > > - hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > > - error_report("vhost backend memory slots limit is less" > > - " than current number of present memory slots"); > > + if (vhost_dev_used_memslots_is_exceeded(hdev)) { > why do you keep this check? > it seems always be false > > > > > r = -1; > > goto fail; > > } > > @@ -1341,6 +1350,16 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > > hdev->memory_changed = false; > > memory_listener_register(&hdev->memory_listener, &address_space_memory); > > QLIST_INSERT_HEAD(&vhost_devices, hdev, entry); > > + > > + if (vhost_dev_used_memslots_is_exceeded(hdev)) { > > + r = -1; > > + if (busyloop_timeout) { > > + goto fail_busyloop; > > + } else { > > + goto fail; > > + } > > + } > seem to be right thing to do, since after registering listener for the first time > used_memslots will be updated to actual value. > > > I did some testing and without this hunk/patch > > on 'device_add virtio-net-pci,netdev=net0' qemu prints: > > qemu-system-x86_64: vhost_set_mem_table failed: Argument list too long (7) > qemu-system-x86_64: unable to start vhost net: 7: falling back on userspace virtio > > and network is operational in guest, but with this patch > > "netdev_add ...,vhost-on" prints: > > vhost backend memory slots limit is less than current number of present memory slots > vhost-net requested but could not be initialized > > and following "device_add virtio-net-pci,netdev=net0" prints: > > TUNSETOFFLOAD ioctl() failed: Bad file descriptor > TUNSETOFFLOAD ioctl() failed: Bad file descriptor > > adapter is still hot-plugged but guest networking is broken (can't get IP address via DHCP) > > so patch seems introduces a regression or something broken elsewhere and this exposes issue, > not sure what qemu reaction should be in this case > i.e. when netdev_add fails > 1: should we fail followed up device_add or > 2: make it fall back to userspace virtio > > I'd go for #2, > Michael what's your take on it? OK but there's a vhost force flag, if that is set we definitely should fail device_add. Also, hotplug can follow device_add, should be handled similarly. > > + > > return 0; > > > > fail_busyloop:
> -----Original Message----- > From: Igor Mammedov [mailto:imammedo@redhat.com] > Sent: Saturday, December 23, 2017 2:49 AM > To: Zhoujian (jay) <jianjay.zhou@huawei.com> > Cc: qemu-devel@nongnu.org; mst@redhat.com; Huangweidong (C) > <weidong.huang@huawei.com>; Gonglei (Arei) <arei.gonglei@huawei.com>; > wangxin (U) <wangxinxin.wang@huawei.com>; Liuzhe (Cloud Open Labs, NFV) > <gary.liuzhe@huawei.com>; dgilbert@redhat.com > Subject: Re: [PATCH v2 2/2] vhost: double check used memslots number > > On Fri, 15 Dec 2017 16:45:55 +0800 > Jay Zhou <jianjay.zhou@huawei.com> wrote: > > > If the VM already has N(N>8) available memory slots for vhost user, > > the VM will be crashed in vhost_user_set_mem_table if we try to > > hotplug the first vhost user NIC. > > This patch checks if memslots number exceeded or not after updating > > vhost_user_used_memslots. > Can't understand commit message, pls rephrase (what is being fixed, and > how it's fixed) also include reproducing steps for crash and maybe > describe call flow/backtrace that triggers crash. Sorry about my pool english > > PS: > I wasn't able to reproduce crash Steps to reproduce: (1) start up a VM successfully without any vhost device (2) hotplug 8 DIMM memory successfully (3) hotplug a vhost-user NIC, the VM crashed, it asserted at the line assert(fd_num < VHOST_MEMORY_MAX_NREGIONS); in vhost_user_set_mem_table() Regards, Jay > > > > Signed-off-by: Jay Zhou <jianjay.zhou@huawei.com> > > --- > > hw/virtio/vhost.c | 27 +++++++++++++++++++++++---- > > 1 file changed, 23 insertions(+), 4 deletions(-) > > > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index > > 59a32e9..e45f5e2 100644 > > --- a/hw/virtio/vhost.c > > +++ b/hw/virtio/vhost.c > > @@ -1234,6 +1234,18 @@ static void vhost_virtqueue_cleanup(struct > vhost_virtqueue *vq) > > event_notifier_cleanup(&vq->masked_notifier); > > } > > > > +static bool vhost_dev_used_memslots_is_exceeded(struct vhost_dev > > +*hdev) { > > + if (hdev->vhost_ops->vhost_get_used_memslots() > > > + hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > > + error_report("vhost backend memory slots limit is less" > > + " than current number of present memory slots"); > > + return true; > > + } > > + > > + return false; > > +} > > + > > int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > > VhostBackendType backend_type, uint32_t > > busyloop_timeout) { @@ -1252,10 +1264,7 @@ int vhost_dev_init(struct > > vhost_dev *hdev, void *opaque, > > goto fail; > > } > > > > - if (hdev->vhost_ops->vhost_get_used_memslots() > > > - hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > > - error_report("vhost backend memory slots limit is less" > > - " than current number of present memory slots"); > > + if (vhost_dev_used_memslots_is_exceeded(hdev)) { > why do you keep this check? > it seems always be false > > > > > r = -1; > > goto fail; > > } > > @@ -1341,6 +1350,16 @@ int vhost_dev_init(struct vhost_dev *hdev, void > *opaque, > > hdev->memory_changed = false; > > memory_listener_register(&hdev->memory_listener, > &address_space_memory); > > QLIST_INSERT_HEAD(&vhost_devices, hdev, entry); > > + > > + if (vhost_dev_used_memslots_is_exceeded(hdev)) { > > + r = -1; > > + if (busyloop_timeout) { > > + goto fail_busyloop; > > + } else { > > + goto fail; > > + } > > + } > seem to be right thing to do, since after registering listener for the > first time used_memslots will be updated to actual value. > > > I did some testing and without this hunk/patch > > on 'device_add virtio-net-pci,netdev=net0' qemu prints: > > qemu-system-x86_64: vhost_set_mem_table failed: Argument list too long (7) > qemu-system-x86_64: unable to start vhost net: 7: falling back on > userspace virtio > > and network is operational in guest, but with this patch > > "netdev_add ...,vhost-on" prints: > > vhost backend memory slots limit is less than current number of present > memory slots vhost-net requested but could not be initialized > > and following "device_add virtio-net-pci,netdev=net0" prints: > > TUNSETOFFLOAD ioctl() failed: Bad file descriptor TUNSETOFFLOAD ioctl() > failed: Bad file descriptor > > adapter is still hot-plugged but guest networking is broken (can't get IP > address via DHCP) > > so patch seems introduces a regression or something broken elsewhere and > this exposes issue, not sure what qemu reaction should be in this case > i.e. when netdev_add fails > 1: should we fail followed up device_add or > 2: make it fall back to userspace virtio > > I'd go for #2, > Michael what's your take on it? > > > + > > return 0; > > > > fail_busyloop:
[...] > > --- > > hw/virtio/vhost.c | 27 +++++++++++++++++++++++---- > > 1 file changed, 23 insertions(+), 4 deletions(-) > > > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index > > 59a32e9..e45f5e2 100644 > > --- a/hw/virtio/vhost.c > > +++ b/hw/virtio/vhost.c > > @@ -1234,6 +1234,18 @@ static void vhost_virtqueue_cleanup(struct > vhost_virtqueue *vq) > > event_notifier_cleanup(&vq->masked_notifier); > > } > > > > +static bool vhost_dev_used_memslots_is_exceeded(struct vhost_dev > > +*hdev) { > > + if (hdev->vhost_ops->vhost_get_used_memslots() > > > + hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > > + error_report("vhost backend memory slots limit is less" > > + " than current number of present memory slots"); > > + return true; > > + } > > + > > + return false; > > +} > > + > > int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > > VhostBackendType backend_type, uint32_t > > busyloop_timeout) { @@ -1252,10 +1264,7 @@ int vhost_dev_init(struct > > vhost_dev *hdev, void *opaque, > > goto fail; > > } > > > > - if (hdev->vhost_ops->vhost_get_used_memslots() > > > - hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > > - error_report("vhost backend memory slots limit is less" > > - " than current number of present memory slots"); > > + if (vhost_dev_used_memslots_is_exceeded(hdev)) { > why do you keep this check? > it seems always be false > If a vhost device has been already added successfully, i.e. its memory Listener has been registered, i.e. hdev->vhost_ops->vhost_set_used_memslots() has been called(used_memslots is updated here), then if we hotplug another same backend type vhost device, hdev->vhost_ops->vhost_get_used_memslots() will not be 0( used_memslots is the same for the same type backend vhost device), so it will not always be false. Regards, Jay
On Fri, 22 Dec 2017 23:15:09 +0200 "Michael S. Tsirkin" <mst@redhat.com> wrote: > On Fri, Dec 22, 2017 at 07:48:55PM +0100, Igor Mammedov wrote: > > On Fri, 15 Dec 2017 16:45:55 +0800 > > Jay Zhou <jianjay.zhou@huawei.com> wrote: > > > > > If the VM already has N(N>8) available memory slots for vhost user, > > > the VM will be crashed in vhost_user_set_mem_table if we try to > > > hotplug the first vhost user NIC. > > > This patch checks if memslots number exceeded or not after updating > > > vhost_user_used_memslots. > > Can't understand commit message, pls rephrase (what is being fixed, and how it's fixed) > > also include reproducing steps for crash and maybe describe call flow/backtrace > > that triggers crash. > > > > PS: > > I wasn't able to reproduce crash > > > > > > > > Signed-off-by: Jay Zhou <jianjay.zhou@huawei.com> > > > --- > > > hw/virtio/vhost.c | 27 +++++++++++++++++++++++---- > > > 1 file changed, 23 insertions(+), 4 deletions(-) > > > > > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > > > index 59a32e9..e45f5e2 100644 > > > --- a/hw/virtio/vhost.c > > > +++ b/hw/virtio/vhost.c > > > @@ -1234,6 +1234,18 @@ static void vhost_virtqueue_cleanup(struct vhost_virtqueue *vq) > > > event_notifier_cleanup(&vq->masked_notifier); > > > } > > > > > > +static bool vhost_dev_used_memslots_is_exceeded(struct vhost_dev *hdev) > > > +{ > > > + if (hdev->vhost_ops->vhost_get_used_memslots() > > > > + hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > > > + error_report("vhost backend memory slots limit is less" > > > + " than current number of present memory slots"); > > > + return true; > > > + } > > > + > > > + return false; > > > +} > > > + > > > int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > > > VhostBackendType backend_type, uint32_t busyloop_timeout) > > > { > > > @@ -1252,10 +1264,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > > > goto fail; > > > } > > > > > > - if (hdev->vhost_ops->vhost_get_used_memslots() > > > > - hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > > > - error_report("vhost backend memory slots limit is less" > > > - " than current number of present memory slots"); > > > + if (vhost_dev_used_memslots_is_exceeded(hdev)) { > > why do you keep this check? > > it seems always be false > > > > > > > > > r = -1; > > > goto fail; > > > } > > > @@ -1341,6 +1350,16 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > > > hdev->memory_changed = false; > > > memory_listener_register(&hdev->memory_listener, &address_space_memory); > > > QLIST_INSERT_HEAD(&vhost_devices, hdev, entry); > > > + > > > + if (vhost_dev_used_memslots_is_exceeded(hdev)) { > > > + r = -1; > > > + if (busyloop_timeout) { > > > + goto fail_busyloop; > > > + } else { > > > + goto fail; > > > + } > > > + } > > seem to be right thing to do, since after registering listener for the first time > > used_memslots will be updated to actual value. > > > > > > I did some testing and without this hunk/patch > > > > on 'device_add virtio-net-pci,netdev=net0' qemu prints: > > > > qemu-system-x86_64: vhost_set_mem_table failed: Argument list too long (7) > > qemu-system-x86_64: unable to start vhost net: 7: falling back on userspace virtio > > > > and network is operational in guest, but with this patch > > > > "netdev_add ...,vhost-on" prints: > > > > vhost backend memory slots limit is less than current number of present memory slots > > vhost-net requested but could not be initialized > > > > and following "device_add virtio-net-pci,netdev=net0" prints: > > > > TUNSETOFFLOAD ioctl() failed: Bad file descriptor > > TUNSETOFFLOAD ioctl() failed: Bad file descriptor > > > > adapter is still hot-plugged but guest networking is broken (can't get IP address via DHCP) > > > > so patch seems introduces a regression or something broken elsewhere and this exposes issue, > > not sure what qemu reaction should be in this case > > i.e. when netdev_add fails > > 1: should we fail followed up device_add or > > 2: make it fall back to userspace virtio > > > > I'd go for #2, > > Michael what's your take on it? > > OK but there's a vhost force flag, if that is set we definitely should > fail device_add. > > Also, hotplug can follow device_add, should be handled similarly. I was testing with vhost-kernel (as it doesn't need extra environment to setup) and it's able to fallback to virtio transport. However in case of vhost-user, is there even an option to fallback to? Perhaps our only choice here is to fail backend creation cleanly, so no one would be able to add a frontend refering to non existing backend. PS: even if we have to fail on error for vhost-user, this patch shouldn't change current vhost-kernel behavior (fallback should still work) > > > > + > > > return 0; > > > > > > fail_busyloop: >
> -----Original Message----- > From: Igor Mammedov [mailto:imammedo@redhat.com] > Sent: Thursday, December 28, 2017 7:29 PM > To: Michael S. Tsirkin <mst@redhat.com> > Cc: Huangweidong (C) <weidong.huang@huawei.com>; wangxin (U) > <wangxinxin.wang@huawei.com>; qemu-devel@nongnu.org; Liuzhe (Cloud Open > Labs, NFV) <gary.liuzhe@huawei.com>; dgilbert@redhat.com; Gonglei (Arei) > <arei.gonglei@huawei.com>; Zhoujian (jay) <jianjay.zhou@huawei.com> > Subject: Re: [Qemu-devel] [PATCH v2 2/2] vhost: double check used memslots > number > > On Fri, 22 Dec 2017 23:15:09 +0200 > "Michael S. Tsirkin" <mst@redhat.com> wrote: > > > On Fri, Dec 22, 2017 at 07:48:55PM +0100, Igor Mammedov wrote: > > > On Fri, 15 Dec 2017 16:45:55 +0800 > > > Jay Zhou <jianjay.zhou@huawei.com> wrote: > > > > > > > If the VM already has N(N>8) available memory slots for vhost > > > > user, the VM will be crashed in vhost_user_set_mem_table if we try > > > > to hotplug the first vhost user NIC. > > > > This patch checks if memslots number exceeded or not after > > > > updating vhost_user_used_memslots. > > > Can't understand commit message, pls rephrase (what is being fixed, > > > and how it's fixed) also include reproducing steps for crash and > > > maybe describe call flow/backtrace that triggers crash. > > > > > > PS: > > > I wasn't able to reproduce crash > > > > > > > > > > > Signed-off-by: Jay Zhou <jianjay.zhou@huawei.com> > > > > --- > > > > hw/virtio/vhost.c | 27 +++++++++++++++++++++++---- > > > > 1 file changed, 23 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index > > > > 59a32e9..e45f5e2 100644 > > > > --- a/hw/virtio/vhost.c > > > > +++ b/hw/virtio/vhost.c > > > > @@ -1234,6 +1234,18 @@ static void vhost_virtqueue_cleanup(struct > vhost_virtqueue *vq) > > > > event_notifier_cleanup(&vq->masked_notifier); > > > > } > > > > > > > > +static bool vhost_dev_used_memslots_is_exceeded(struct vhost_dev > > > > +*hdev) { > > > > + if (hdev->vhost_ops->vhost_get_used_memslots() > > > > > + hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > > > > + error_report("vhost backend memory slots limit is less" > > > > + " than current number of present memory slots"); > > > > + return true; > > > > + } > > > > + > > > > + return false; > > > > +} > > > > + > > > > int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > > > > VhostBackendType backend_type, uint32_t > > > > busyloop_timeout) { @@ -1252,10 +1264,7 @@ int > > > > vhost_dev_init(struct vhost_dev *hdev, void *opaque, > > > > goto fail; > > > > } > > > > > > > > - if (hdev->vhost_ops->vhost_get_used_memslots() > > > > > - hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { > > > > - error_report("vhost backend memory slots limit is less" > > > > - " than current number of present memory slots"); > > > > + if (vhost_dev_used_memslots_is_exceeded(hdev)) { > > > why do you keep this check? > > > it seems always be false > > > > > > > > > > > > > r = -1; > > > > goto fail; > > > > } > > > > @@ -1341,6 +1350,16 @@ int vhost_dev_init(struct vhost_dev *hdev, > void *opaque, > > > > hdev->memory_changed = false; > > > > memory_listener_register(&hdev->memory_listener, > &address_space_memory); > > > > QLIST_INSERT_HEAD(&vhost_devices, hdev, entry); > > > > + > > > > + if (vhost_dev_used_memslots_is_exceeded(hdev)) { > > > > + r = -1; > > > > + if (busyloop_timeout) { > > > > + goto fail_busyloop; > > > > + } else { > > > > + goto fail; > > > > + } > > > > + } > > > seem to be right thing to do, since after registering listener for > > > the first time used_memslots will be updated to actual value. > > > > > > > > > I did some testing and without this hunk/patch > > > > > > on 'device_add virtio-net-pci,netdev=net0' qemu prints: > > > > > > qemu-system-x86_64: vhost_set_mem_table failed: Argument list too > > > long (7) > > > qemu-system-x86_64: unable to start vhost net: 7: falling back on > > > userspace virtio Error code 7 is E2BIG, which means if (mem.nregions > max_mem_regions) return -E2BIG; happened in the kernel. > > > > > > and network is operational in guest, but with this patch > > > > > > "netdev_add ...,vhost-on" prints: > > > > > > vhost backend memory slots limit is less than current number of > > > present memory slots vhost-net requested but could not be > > > initialized > > > > > > and following "device_add virtio-net-pci,netdev=net0" prints: > > > > > > TUNSETOFFLOAD ioctl() failed: Bad file descriptor TUNSETOFFLOAD > > > ioctl() failed: Bad file descriptor > > > > > > adapter is still hot-plugged but guest networking is broken (can't > > > get IP address via DHCP) > > > > > > so patch seems introduces a regression or something broken elsewhere > > > and this exposes issue, not sure what qemu reaction should be in > > > this case i.e. when netdev_add fails > > > 1: should we fail followed up device_add or > > > 2: make it fall back to userspace virtio > > > > > > I'd go for #2, > > > Michael what's your take on it? > > > > OK but there's a vhost force flag, if that is set we definitely should > > fail device_add. > > > > Also, hotplug can follow device_add, should be handled similarly. > I was testing with vhost-kernel (as it doesn't need extra environment to > setup) and it's able to fallback to virtio transport. > > However in case of vhost-user, is there even an option to fallback to? Using error code(which do it like vhost-kernel) instead of asserting in vhost_user_set_mem_table(), I have tested: "netdev_add vhost-user,chardev=charnet0,id=hostnet0" is successful, following "device_add virtio-net-pci,netdev=hostnet0,id=net0,bus=pci.0" prints: "qemu-system-x86_64: vhost_set_mem_table failed: Interrupted system call (4) qemu-system-x86_64: unable to start vhost net: 4: falling back on userspace virtio" or "qemu-system-x86_64: vhost_set_mem_table failed: Resource temporarily unavailable (11) qemu-system-x86_64: unable to start vhost net: 11: falling back on userspace virtio" adapter is still hot-plugged but guest networking is broken (can't get IP address via DHCP), does this mean make no sense for vhost-user to fallback to? > Perhaps our only choice here is to fail backend creation cleanly, so no > one would be able to add a frontend refering to non existing backend. Not sure what to do. > > > PS: > even if we have to fail on error for vhost-user, this patch shouldn't > change current vhost-kernel behavior (fallback should still work) Does it mean vhost-kernel don't need to care about the value of used_memslots (because it's able to fall back to userspace virtio)? Is it enough to use error code in vhost_user_set_mem_table() and vhost_kernel_set_mem_table()? 1. If yes, how about removing the check of used_memslots totally? 2. If no, is it enough to check used_memslots for vhost-user only after memory listener is registered? Regards, Jay > > > > > > > + > > > > return 0; > > > > > > > > fail_busyloop: > >
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index 59a32e9..e45f5e2 100644 --- a/hw/virtio/vhost.c +++ b/hw/virtio/vhost.c @@ -1234,6 +1234,18 @@ static void vhost_virtqueue_cleanup(struct vhost_virtqueue *vq) event_notifier_cleanup(&vq->masked_notifier); } +static bool vhost_dev_used_memslots_is_exceeded(struct vhost_dev *hdev) +{ + if (hdev->vhost_ops->vhost_get_used_memslots() > + hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { + error_report("vhost backend memory slots limit is less" + " than current number of present memory slots"); + return true; + } + + return false; +} + int vhost_dev_init(struct vhost_dev *hdev, void *opaque, VhostBackendType backend_type, uint32_t busyloop_timeout) { @@ -1252,10 +1264,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque, goto fail; } - if (hdev->vhost_ops->vhost_get_used_memslots() > - hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) { - error_report("vhost backend memory slots limit is less" - " than current number of present memory slots"); + if (vhost_dev_used_memslots_is_exceeded(hdev)) { r = -1; goto fail; } @@ -1341,6 +1350,16 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque, hdev->memory_changed = false; memory_listener_register(&hdev->memory_listener, &address_space_memory); QLIST_INSERT_HEAD(&vhost_devices, hdev, entry); + + if (vhost_dev_used_memslots_is_exceeded(hdev)) { + r = -1; + if (busyloop_timeout) { + goto fail_busyloop; + } else { + goto fail; + } + } + return 0; fail_busyloop:
If the VM already has N(N>8) available memory slots for vhost user, the VM will be crashed in vhost_user_set_mem_table if we try to hotplug the first vhost user NIC. This patch checks if memslots number exceeded or not after updating vhost_user_used_memslots. Signed-off-by: Jay Zhou <jianjay.zhou@huawei.com> --- hw/virtio/vhost.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-)