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path: root/include/linux/virtio_ring.h
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2012-01-12virtio: harsher barriers for rpmsg.Rusty Russell1-0/+1
We were cheating with our barriers; using the smp ones rather than the real device ones. That was fine, until rpmsg came along, which is used to talk to a real device (a non-SMP CPU). Unfortunately, just putting back the real barriers (reverting d57ed95d) causes a performance regression on virtio-pci. In particular, Amos reports netbench's TCP_RR over virtio_net CPU utilization increased up to 35% while throughput went down by up to 14%. By comparison, this branch is in the noise. Reference: https://lkml.org/lkml/2011/12/11/22 Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2011-11-02virtio: modify vring_init and vring_size to take account of the layout ↵Wang Sheng-Hui1-3/+3
containing *_event_idx Based on the layout description in the comments, take account of the *_event_idx in functions vring_init and vring_size. Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2011-05-30virtio ring: inline function to check for eventsMichael S. Tsirkin1-0/+14
With the new used_event and avail_event and features, both host and guest need similar logic to check whether events are enabled, so it helps to put the common code in the header. Note that Xen has similar logic for notification hold-off in include/xen/interface/io/ring.h with req_event and req_prod corresponding to event_idx + 1 and new_idx respectively. +1 comes from the fact that req_event and req_prod in Xen start at 1, while event index in virtio starts at 0. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2011-05-30virtio: event index interfaceMichael S. Tsirkin1-1/+14
Define a new feature bit for the guest and host to utilize an event index (like Xen) instead if a flag bit to enable/disable interrupts and kicks. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2011-05-30virtio: add full three-clause BSD text to headers.Rusty Russell1-0/+23
It's unclear to me if it's important, but it's obviously causing my technical colleages some headaches and I'd hate such imprecision to slow virtio adoption. I've emailed this to all non-trivial contributors for approval, too. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Grant Likely <grant.likely@secretlab.ca> Acked-by: Ryan Harper <ryanh@us.ibm.com> Acked-by: Anthony Liguori <aliguori@us.ibm.com> Acked-by: Eric Van Hensbergen <ericvh@gmail.com> Acked-by: john cooper <john.cooper@redhat.com> Acked-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
2009-07-30lguest and virtio: cleanup struct definitions to Linux style.Rusty Russell1-8/+4
I've been doing this for years, and akpm picked me up on it about 12 months ago. lguest partly serves as example code, so let's do it Right. Also, remove two unused fields in struct vblk_info in the example launcher. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Ingo Molnar <mingo@redhat.com>
2009-06-12virtio: indirect ring entries (VIRTIO_RING_F_INDIRECT_DESC)Mark McLoughlin1-0/+5
Add a new feature flag for indirect ring entries. These are ring entries which point to a table of buffer descriptors. The idea here is to increase the ring capacity by allowing a larger effective ring size whereby the ring size dictates the number of requests that may be outstanding, rather than the size of those requests. This should be most effective in the case of block I/O where we can potentially benefit by concurrently dispatching a large number of large requests. Even in the simple case of single segment block requests, this results in a threefold increase in ring capacity. Signed-off-by: Mark McLoughlin <markmc@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2009-06-12virtio: add names to virtqueue struct, mapping from devices to queues.Rusty Russell1-1/+2
Add a linked list of all virtqueues for a virtio device: this helps for debugging and is also needed for upcoming interface change. Also, add a "name" field for clearer debug messages. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-12-30virtio: hand virtio ring alignment as argument to vring_new_virtqueueRusty Russell1-0/+1
This allows each virtio user to hand in the alignment appropriate to their virtio_ring structures. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
2008-12-30virtio: rename 'pagesize' arg to vring_init/vring_sizeRusty Russell1-6/+6
It's really the alignment desired for consumer/producer separation; historically this x86 pagesize, but with PowerPC it'll still be x86 pagesize. And in theory lguest could choose a different value. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-07-25virtio: Add transport feature handling stub for virtio_ring.Rusty Russell1-0/+2
To prepare for virtio_ring transport feature bits, hook in a call in all the users to manipulate them. This currently just clears all the bits, since it doesn't understand any features. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: clarify NO_NOTIFY flag usageRusty Russell1-2/+6
The other side (host) can set the NO_NOTIFY flag as an optimization, to say "no need to kick me when you add things". Make it clear that this is advisory only; especially that we should always notify when the ring is full. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: Fix vring_init/vring_size to take unsigned longAnthony Liguori1-2/+2
Using unsigned int resulted in silent truncation of the upper 32-bit on x86_64 resulting in an OOPS since the ring was being initialized wrong. Please reconsider my previous patch to just use PAGE_ALIGN(). Open coding this sort of stuff, no matter how simple it seems, is just asking for this sort of trouble. Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: explicit enable_cb/disable_cb rather than callback return.Rusty Russell1-1/+1
It seems that virtio_net wants to disable callbacks (interrupts) before calling netif_rx_schedule(), so we can't use the return value to do so. Rename "restart" to "cb_enable" and introduce "cb_disable" hook: callback now returns void, rather than a boolean. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2007-11-12virtio: Force use of power-of-two for descriptor ring sizesRusty Russell1-8/+11
The virtio descriptor rings of size N-1 were nicely set up to be aligned to an N-byte boundary. But as Anthony Liguori points out, the free-running indices used by virtio require that the sizes be a power of 2, otherwise we get problems on wrap (demonstrated with lguest). So we replace the clever "2^n-1" scheme with a simple "align to page boundary" scheme: this means that all virtio rings take at least two pages, but it's safer than guessing cache alignment. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2007-11-12virtio: fix vring_init for 64 bitsAnthony Liguori1-2/+2
This patch fixes a typo in vring_init(). This happens to work today in lguest because the sizeof(struct vring_desc) is 16 and struct vring contains 3 pointers and an unsigned int so on 32-bit sizeof(struct vring_desc) == sizeof(struct vring). However, this is no longer true on 64-bit where the bug is exposed. Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2007-10-23Virtio helper routines for a descriptor ringbuffer implementationRusty Russell1-0/+119
These helper routines supply most of the virtqueue_ops for hypervisors which want to use a ring for virtio. Unlike the previous lguest implementation: 1) The rings are variable sized (2^n-1 elements). 2) They have an unfortunate limit of 65535 bytes per sg element. 3) The page numbers are always 64 bit (PAE anyone?) 4) They no longer place used[] on a separate page, just a separate cacheline. 5) We do a modulo on a variable. We could be tricky if we cared. 6) Interrupts and notifies are suppressed using flags within the rings. Users need only get the ring pages and provide a notify hook (KVM wants the guest to allocate the rings, lguest does it sanely). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Dor Laor <dor.laor@qumranet.com>