search for: last_seen_us

Patches before the last are small cleanups. In the last patch I'm trying to extract / generalize an idea from Stefan Hajnoczi's review of my virtio-net driver for OVMF. Unfortunately I can't find Stefan's email on any mailing list archive (sourceforge, gmane, mail-archive etc. all have only my response), so I'll quote it here. The patch Stefan was reviewing is

Patches before the last are small cleanups. In the last patch I'm trying to extract / generalize an idea from Stefan Hajnoczi's review of my virtio-net driver for OVMF. Unfortunately I can't find Stefan's email on any mailing list archive (sourceforge, gmane, mail-archive etc. all have only my response), so I'll quote it here. The patch Stefan was reviewing is

Changes from v2: added padding between avail idx and flags, and changed virtio to only publish used index when callbacks are enabled. Here's a rewrite of the original patch with a new layout. I haven't tested it yet so no idea how this performs, but I think this addresses the cache bounce issue raised by Avi. Posting for early flames/comments. Generally, the Host end of the virtio ring

Changes from v2: added padding between avail idx and flags, and changed virtio to only publish used index when callbacks are enabled. Here's a rewrite of the original patch with a new layout. I haven't tested it yet so no idea how this performs, but I think this addresses the cache bounce issue raised by Avi. Posting for early flames/comments. Generally, the Host end of the virtio ring

Here's a rewrite of the original patch with a new layout. I haven't tested it yet so no idea how this performs, but I think this addresses the cache bounce issue raised by Avi. Posting for early flames/comments. Generally, the Host end of the virtio ring doesn't need to see where Guest is up to in consuming the ring. However, to completely understand what's going on from the

Here's a rewrite of the original patch with a new layout. I haven't tested it yet so no idea how this performs, but I think this addresses the cache bounce issue raised by Avi. Posting for early flames/comments. Generally, the Host end of the virtio ring doesn't need to see where Guest is up to in consuming the ring. However, to completely understand what's going on from the

...eware the problem of missing notifications between emptying the ring and reenabling no- tifications. This is usually handled by re-checking for more used buffers after notifications are re- enabled: virtq_disable_used_buffer_notifications(vq); for (;;) { if (vq->last_seen_used != le16_to_cpu(virtq->used.idx)) { virtq_enable_used_buffer_notifications(vq); mb(); if (vq->last_seen_used != le16_to_cpu(virtq->used.idx)) break; virtq_disable_used_buffer_notifications(vq); } struct virtq_used_elem *e = virtq.used->ri...

Folks, We came across a memory race condition between VPP vhost driver and the kernel vhost. VPP is running a tap interface over vhost backend. In this case, VPP is acting as the vhost driver mode and the kernel vhost is acting as the vhost device mode. In the kernel vhost?s TX traffic direction which is VPP?s RX traffic direction, kernel vhost is the producer and VPP is the consumer. Kernel

Folks, We came across a memory race condition between VPP vhost driver and the kernel vhost. VPP is running a tap interface over vhost backend. In this case, VPP is acting as the vhost driver mode and the kernel vhost is acting as the vhost device mode. In the kernel vhost?s TX traffic direction which is VPP?s RX traffic direction, kernel vhost is the producer and VPP is the consumer. Kernel

...ng the used ring, but beware the problem of missing notifications between emptying the ring and reenabling no- tifications. This is usually handled by re-checking for more used buffers after notifications are re- enabled: virtq_disable_used_buffer_notifications(vq); for (;;) { if (vq->last_seen_used != le16_to_cpu(virtq->used.idx)) { virtq_enable_used_buffer_notifications(vq); mb(); if (vq->last_seen_used != le16_to_cpu(virtq->used.idx)) break; virtq_disable_used_buffer_notifications(vq); } struct virtq_used_elem *e = virtq.used->ring[vq->last_seen_used%vsz...

...pty condition. + This is necessary to handle the case where, after the last check and before + enabling interrupts, an interrupt has been suppressed by the device: +\end_layout + +\begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout -while (vq->last_seen_used != vring->used.idx) { +\change_inserted 0 1304342051 + +vring_disable_interrupts(vq); +\end_layout + +\begin_layout Plain Layout + +\change_inserted 0 1304341878 + +for (;;) { +\end_layout + +\begin_layout Plain Layout + +\change_inserted 0 1304341880 + + if +\change_deleted 0 1304341882 +...

...pty condition. + This is necessary to handle the case where, after the last check and before + enabling interrupts, an interrupt has been suppressed by the device: +\end_layout + +\begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout -while (vq->last_seen_used != vring->used.idx) { +\change_inserted 0 1304342051 + +vring_disable_interrupts(vq); +\end_layout + +\begin_layout Plain Layout + +\change_inserted 0 1304341878 + +for (;;) { +\end_layout + +\begin_layout Plain Layout + +\change_inserted 0 1304341880 + + if +\change_deleted 0 1304341882 +...

...pty condition. + This is necessary to handle the case where, after the last check and before + enabling interrupts, an interrupt has been suppressed by the device: +\end_layout + +\begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout -while (vq->last_seen_used != vring->used.idx) { +\change_inserted 1 1304342051 + +vring_disable_interrupts(vq); +\end_layout + +\begin_layout Plain Layout + +\change_inserted 1 1304341878 + +for (;;) { +\end_layout + +\begin_layout Plain Layout + +\change_inserted 1 1304341880 + + if +\change_deleted 1 1304341882 +...

...pty condition. + This is necessary to handle the case where, after the last check and before + enabling interrupts, an interrupt has been suppressed by the device: +\end_layout + +\begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout -while (vq->last_seen_used != vring->used.idx) { +\change_inserted 1 1304342051 + +vring_disable_interrupts(vq); +\end_layout + +\begin_layout Plain Layout + +\change_inserted 1 1304341878 + +for (;;) { +\end_layout + +\begin_layout Plain Layout + +\change_inserted 1 1304341880 + + if +\change_deleted 1 1304341882 +...