similar to: [PATCH] vhost: Fix warnings and bad type handling

This patch move the used ring initialization after backend was set. This make us possible to disable the backend and tweak the used ring then restart. And it's also useful for log setting as used ring have been checked then. Signed-off-by: Jason Wang <jasowang at redhat.com> --- drivers/vhost/net.c | 4 ++++ drivers/vhost/vhost.c | 11 +++-------- drivers/vhost/vhost.h | 1 +

This patch move the used ring initialization after backend was set. This make us possible to disable the backend and tweak the used ring then restart. And it's also useful for log setting as used ring have been checked then. Signed-off-by: Jason Wang <jasowang at redhat.com> --- drivers/vhost/net.c | 4 ++++ drivers/vhost/vhost.c | 11 +++-------- drivers/vhost/vhost.h | 1 +

We need to set log when updating flags of used ring, otherwise they may be missed after migration. A helper was introduced to write used_flags back to guest memory and update the log if necessary. Signed-off-by: Jason Wang <jasowang at redhat.com> --- drivers/vhost/vhost.c | 26 ++++++++++++++++++++++---- drivers/vhost/vhost.h | 2 ++ 2 files changed, 24 insertions(+), 4 deletions(-)

We need to set log when updating flags of used ring, otherwise they may be missed after migration. A helper was introduced to write used_flags back to guest memory and update the log if necessary. Signed-off-by: Jason Wang <jasowang at redhat.com> --- drivers/vhost/vhost.c | 26 ++++++++++++++++++++++---- drivers/vhost/vhost.h | 2 ++ 2 files changed, 24 insertions(+), 4 deletions(-)

On biarch kernels, it is not safe to do copy from/to user, even with use_mm, unless we checked the address range with access_ok previously. Implement these checks to enforce safe memory accesses. Reported-by: Al Viro <viro at zeniv.linux.org.uk> Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/vhost/net.c | 17 ++++++- drivers/vhost/vhost.c | 111

On biarch kernels, it is not safe to do copy from/to user, even with use_mm, unless we checked the address range with access_ok previously. Implement these checks to enforce safe memory accesses. Reported-by: Al Viro <viro at zeniv.linux.org.uk> Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/vhost/net.c | 17 ++++++- drivers/vhost/vhost.c | 111

With PUBLISH_USED_IDX, guest tells us which used entries it has consumed. This can be used to reduce the number of interrupts: after we write a used entry, if the guest has not yet consumed the previous entry, or if the guest has already consumed the new entry, we do not need to interrupt. This imporves bandwidth by 30% under some workflows. Signed-off-by: Michael S. Tsirkin <mst at

With PUBLISH_USED_IDX, guest tells us which used entries it has consumed. This can be used to reduce the number of interrupts: after we write a used entry, if the guest has not yet consumed the previous entry, or if the guest has already consumed the new entry, we do not need to interrupt. This imporves bandwidth by 30% under some workflows. Signed-off-by: Michael S. Tsirkin <mst at

With PUBLISH_USED_IDX, guest tells us which used entries it has consumed. This can be used to reduce the number of interrupts: after we write a used entry, if the guest has not yet consumed the previous entry, or if the guest has already consumed the new entry, we do not need to interrupt. This imporves bandwidth by 30% under some workflows. Signed-off-by: Michael S. Tsirkin <mst at

With PUBLISH_USED_IDX, guest tells us which used entries it has consumed. This can be used to reduce the number of interrupts: after we write a used entry, if the guest has not yet consumed the previous entry, or if the guest has already consumed the new entry, we do not need to interrupt. This imporves bandwidth by 30% under some workflows. Signed-off-by: Michael S. Tsirkin <mst at

What it is: vhost net is a character device that can be used to reduce the number of system calls involved in virtio networking. Existing virtio net code is used in the guest without modification. There's similarity with vringfd, with some differences and reduced scope - uses eventfd for signalling - structures can be moved around in memory at any time (good for migration, bug work-arounds

What it is: vhost net is a character device that can be used to reduce the number of system calls involved in virtio networking. Existing virtio net code is used in the guest without modification. There's similarity with vringfd, with some differences and reduced scope - uses eventfd for signalling - structures can be moved around in memory at any time (good for migration, bug work-arounds

P_STREAM can get more than 4GMb/s for the receive side, and more than 5GMb/= s for the send side. Is it the result from the raw socket or through tap? I want to duplicate such performance with vhost on my side. I can only get = more than 1GMb/s with following conditions: 1) disabled the GRO feature in the host 10G NIC driver 2) vi->big_packet in guest is false 3) MTU is 1500. 4) raw socket, not

P_STREAM can get more than 4GMb/s for the receive side, and more than 5GMb/= s for the send side. Is it the result from the raw socket or through tap? I want to duplicate such performance with vhost on my side. I can only get = more than 1GMb/s with following conditions: 1) disabled the GRO feature in the host 10G NIC driver 2) vi->big_packet in guest is false 3) MTU is 1500. 4) raw socket, not

The VHOST_VRING_F_LEGACY_BIG_ENDIAN flag informs the kernel that the associated device is big endian. Of course, this only makes sense for legacy virtio devices since modern virtio devices are always little endian. It will be used by the vhost memory accessors to byteswap vring data when we have a legacy device, in case host and guest endianness differ. Signed-off-by: Greg Kurz <gkurz at

The VHOST_VRING_F_LEGACY_BIG_ENDIAN flag informs the kernel that the associated device is big endian. Of course, this only makes sense for legacy virtio devices since modern virtio devices are always little endian. It will be used by the vhost memory accessors to byteswap vring data when we have a legacy device, in case host and guest endianness differ. Signed-off-by: Greg Kurz <gkurz at

On Mon, Sep 28, 2020 at 02:35:04PM +0200, Greg Kurz wrote: > When the IOTLB device is enabled, the vring addresses we get from > userspace are GIOVAs. It is thus wrong to pass them to vq_access_ok() > which only takes HVAs. The IOTLB map is likely empty at this stage, > so there isn't much that can be done with these GIOVAs. Access validation > will be performed at IOTLB

On Mon, Sep 28, 2020 at 02:35:04PM +0200, Greg Kurz wrote: > When the IOTLB device is enabled, the vring addresses we get from > userspace are GIOVAs. It is thus wrong to pass them to vq_access_ok() > which only takes HVAs. The IOTLB map is likely empty at this stage, > so there isn't much that can be done with these GIOVAs. Access validation > will be performed at IOTLB

It was noticed that the copy_user() friends that was used to access virtqueue metdata tends to be very expensive for dataplane implementation like vhost since it involves lots of software check, speculation barrier, hardware feature toggling (e.g SMAP). The extra cost will be more obvious when transferring small packets. This patch tries to eliminate those overhead by pin vq metadata pages and

On 2019/7/3 ??5:13, Tiwei Bie wrote: > Details about this can be found here: > > https://lwn.net/Articles/750770/ > > What's new in this version > ========================== > > A new VFIO device type is introduced - vfio-vhost. This addressed > some comments from here: https://patchwork.ozlabs.org/cover/984763/ > > Below is the updated device interface: >