diff options
| -rw-r--r-- | arch/x86/lguest/Kconfig | 1 | ||||
| -rw-r--r-- | drivers/virtio/Kconfig | 5 | ||||
| -rw-r--r-- | drivers/virtio/Makefile | 1 | ||||
| -rw-r--r-- | drivers/virtio/virtio_ring.c | 313 | ||||
| -rw-r--r-- | include/linux/virtio_ring.h | 119 |
5 files changed, 439 insertions, 0 deletions
diff --git a/arch/x86/lguest/Kconfig b/arch/x86/lguest/Kconfig index 0fabf87db99..44dccfd845f 100644 --- a/arch/x86/lguest/Kconfig +++ b/arch/x86/lguest/Kconfig @@ -2,6 +2,7 @@ config LGUEST_GUEST bool "Lguest guest support" select PARAVIRT depends on !X86_PAE + select VIRTIO_RING help Lguest is a tiny in-kernel hypervisor. Selecting this will allow your kernel to boot under lguest. This option will increase diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig index bce84b56a65..9e33fc4da87 100644 --- a/drivers/virtio/Kconfig +++ b/drivers/virtio/Kconfig @@ -1,3 +1,8 @@ # Virtio always gets selected by whoever wants it. config VIRTIO bool + +# Similarly the virtio ring implementation. +config VIRTIO_RING + bool + depends on VIRTIO diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile index af0d57dad3e..f70e40971dd 100644 --- a/drivers/virtio/Makefile +++ b/drivers/virtio/Makefile @@ -1 +1,2 @@ obj-$(CONFIG_VIRTIO) += virtio.o +obj-$(CONFIG_VIRTIO_RING) += virtio_ring.o diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c new file mode 100644 index 00000000000..0e4baca21b8 --- /dev/null +++ b/drivers/virtio/virtio_ring.c @@ -0,0 +1,313 @@ +/* Virtio ring implementation. + * + * Copyright 2007 Rusty Russell IBM Corporation + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + */ +#include <linux/virtio.h> +#include <linux/virtio_ring.h> +#include <linux/device.h> + +#ifdef DEBUG +/* For development, we want to crash whenever the ring is screwed. */ +#define BAD_RING(vq, fmt...) \ + do { dev_err(&vq->vq.vdev->dev, fmt); BUG(); } while(0) +#define START_USE(vq) \ + do { if ((vq)->in_use) panic("in_use = %i\n", (vq)->in_use); (vq)->in_use = __LINE__; mb(); } while(0) +#define END_USE(vq) \ + do { BUG_ON(!(vq)->in_use); (vq)->in_use = 0; mb(); } while(0) +#else +#define BAD_RING(vq, fmt...) \ + do { dev_err(&vq->vq.vdev->dev, fmt); (vq)->broken = true; } while(0) +#define START_USE(vq) +#define END_USE(vq) +#endif + +struct vring_virtqueue +{ + struct virtqueue vq; + + /* Actual memory layout for this queue */ + struct vring vring; + + /* Other side has made a mess, don't try any more. */ + bool broken; + + /* Number of free buffers */ + unsigned int num_free; + /* Head of free buffer list. */ + unsigned int free_head; + /* Number we've added since last sync. */ + unsigned int num_added; + + /* Last used index we've seen. */ + unsigned int last_used_idx; + + /* How to notify other side. FIXME: commonalize hcalls! */ + void (*notify)(struct virtqueue *vq); + +#ifdef DEBUG + /* They're supposed to lock for us. */ + unsigned int in_use; +#endif + + /* Tokens for callbacks. */ + void *data[]; +}; + +#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq) + +static int vring_add_buf(struct virtqueue *_vq, + struct scatterlist sg[], + unsigned int out, + unsigned int in, + void *data) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + unsigned int i, avail, head, uninitialized_var(prev); + + BUG_ON(data == NULL); + BUG_ON(out + in > vq->vring.num); + BUG_ON(out + in == 0); + + START_USE(vq); + + if (vq->num_free < out + in) { + pr_debug("Can't add buf len %i - avail = %i\n", + out + in, vq->num_free); + END_USE(vq); + return -ENOSPC; + } + + /* We're about to use some buffers from the free list. */ + vq->num_free -= out + in; + + head = vq->free_head; + for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) { + vq->vring.desc[i].flags = VRING_DESC_F_NEXT; + vq->vring.desc[i].addr = (page_to_pfn(sg_page(sg))<<PAGE_SHIFT) + + sg->offset; + vq->vring.desc[i].len = sg->length; + prev = i; + sg++; + } + for (; in; i = vq->vring.desc[i].next, in--) { + vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE; + vq->vring.desc[i].addr = (page_to_pfn(sg_page(sg))<<PAGE_SHIFT) + + sg->offset; + vq->vring.desc[i].len = sg->length; + prev = i; + sg++; + } + /* Last one doesn't continue. */ + vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT; + + /* Update free pointer */ + vq->free_head = i; + + /* Set token. */ + vq->data[head] = data; + + /* Put entry in available array (but don't update avail->idx until they + * do sync). FIXME: avoid modulus here? */ + avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num; + vq->vring.avail->ring[avail] = head; + + pr_debug("Added buffer head %i to %p\n", head, vq); + END_USE(vq); + return 0; +} + +static void vring_kick(struct virtqueue *_vq) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + START_USE(vq); + /* Descriptors and available array need to be set before we expose the + * new available array entries. */ + wmb(); + + vq->vring.avail->idx += vq->num_added; + vq->num_added = 0; + + /* Need to update avail index before checking if we should notify */ + mb(); + + if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY)) + /* Prod other side to tell it about changes. */ + vq->notify(&vq->vq); + + END_USE(vq); +} + +static void detach_buf(struct vring_virtqueue *vq, unsigned int head) +{ + unsigned int i; + + /* Clear data ptr. */ + vq->data[head] = NULL; + + /* Put back on free list: find end */ + i = head; + while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) { + i = vq->vring.desc[i].next; + vq->num_free++; + } + + vq->vring.desc[i].next = vq->free_head; + vq->free_head = head; + /* Plus final descriptor */ + vq->num_free++; +} + +/* FIXME: We need to tell other side about removal, to synchronize. */ +static void vring_shutdown(struct virtqueue *_vq) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + unsigned int i; + + for (i = 0; i < vq->vring.num; i++) + detach_buf(vq, i); +} + +static inline bool more_used(const struct vring_virtqueue *vq) +{ + return vq->last_used_idx != vq->vring.used->idx; +} + +static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + void *ret; + unsigned int i; + + START_USE(vq); + + if (!more_used(vq)) { + pr_debug("No more buffers in queue\n"); + END_USE(vq); + return NULL; + } + + i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id; + *len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len; + + if (unlikely(i >= vq->vring.num)) { + BAD_RING(vq, "id %u out of range\n", i); + return NULL; + } + if (unlikely(!vq->data[i])) { + BAD_RING(vq, "id %u is not a head!\n", i); + return NULL; + } + + /* detach_buf clears data, so grab it now. */ + ret = vq->data[i]; + detach_buf(vq, i); + vq->last_used_idx++; + END_USE(vq); + return ret; +} + +static bool vring_restart(struct virtqueue *_vq) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + + START_USE(vq); + BUG_ON(!(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)); + + /* We optimistically turn back on interrupts, then check if there was + * more to do. */ + vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT; + mb(); + if (unlikely(more_used(vq))) { + vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; + END_USE(vq); + return false; + } + + END_USE(vq); + return true; +} + +irqreturn_t vring_interrupt(int irq, void *_vq) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + + if (!more_used(vq)) { + pr_debug("virtqueue interrupt with no work for %p\n", vq); + return IRQ_NONE; + } + + if (unlikely(vq->broken)) + return IRQ_HANDLED; + + pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback); + if (vq->vq.callback && !vq->vq.callback(&vq->vq)) + vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; + + return IRQ_HANDLED; +} + +static struct virtqueue_ops vring_vq_ops = { + .add_buf = vring_add_buf, + .get_buf = vring_get_buf, + .kick = vring_kick, + .restart = vring_restart, + .shutdown = vring_shutdown, +}; + +struct virtqueue *vring_new_virtqueue(unsigned int num, + struct virtio_device *vdev, + void *pages, + void (*notify)(struct virtqueue *), + bool (*callback)(struct virtqueue *)) +{ + struct vring_virtqueue *vq; + unsigned int i; + + vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL); + if (!vq) + return NULL; + + vring_init(&vq->vring, num, pages); + vq->vq.callback = callback; + vq->vq.vdev = vdev; + vq->vq.vq_ops = &vring_vq_ops; + vq->notify = notify; + vq->broken = false; + vq->last_used_idx = 0; + vq->num_added = 0; +#ifdef DEBUG + vq->in_use = false; +#endif + + /* No callback? Tell other side not to bother us. */ + if (!callback) + vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; + + /* Put everything in free lists. */ + vq->num_free = num; + vq->free_head = 0; + for (i = 0; i < num-1; i++) + vq->vring.desc[i].next = i+1; + + return &vq->vq; +} + +void vring_del_virtqueue(struct virtqueue *vq) +{ + kfree(to_vvq(vq)); +} + diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h new file mode 100644 index 00000000000..ac69e7bb5a1 --- /dev/null +++ b/include/linux/virtio_ring.h @@ -0,0 +1,119 @@ +#ifndef _LINUX_VIRTIO_RING_H +#define _LINUX_VIRTIO_RING_H +/* An interface for efficient virtio implementation, currently for use by KVM + * and lguest, but hopefully others soon. Do NOT change this since it will + * break existing servers and clients. + * + * This header is BSD licensed so anyone can use the definitions to implement + * compatible drivers/servers. + * + * Copyright Rusty Russell IBM Corporation 2007. */ +#include <linux/types.h> + +/* This marks a buffer as continuing via the next field. */ +#define VRING_DESC_F_NEXT 1 +/* This marks a buffer as write-only (otherwise read-only). */ +#define VRING_DESC_F_WRITE 2 + +/* This means don't notify other side when buffer added. */ +#define VRING_USED_F_NO_NOTIFY 1 +/* This means don't interrupt guest when buffer consumed. */ +#define VRING_AVAIL_F_NO_INTERRUPT 1 + +/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */ +struct vring_desc +{ + /* Address (guest-physical). */ + __u64 addr; + /* Length. */ + __u32 len; + /* The flags as indicated above. */ + __u16 flags; + /* We chain unused descriptors via this, too */ + __u16 next; +}; + +struct vring_avail +{ + __u16 flags; + __u16 idx; + __u16 ring[]; +}; + +/* u32 is used here for ids for padding reasons. */ +struct vring_used_elem +{ + /* Index of start of used descriptor chain. */ + __u32 id; + /* Total length of the descriptor chain which was used (written to) */ + __u32 len; +}; + +struct vring_used +{ + __u16 flags; + __u16 idx; + struct vring_used_elem ring[]; +}; + +struct vring { + unsigned int num; + + struct vring_desc *desc; + + struct vring_avail *avail; + + struct vring_used *used; +}; + +/* The standard layout for the ring is a continuous chunk of memory which looks + * like this. The used fields will be aligned to a "num+1" boundary. + * + * struct vring + * { + * // The actual descriptors (16 bytes each) + * struct vring_desc desc[num]; + * + * // A ring of available descriptor heads with free-running index. + * __u16 avail_flags; + * __u16 avail_idx; + * __u16 available[num]; + * + * // Padding so a correctly-chosen num value will cache-align used_idx. + * char pad[sizeof(struct vring_desc) - sizeof(avail_flags)]; + * + * // A ring of used descriptor heads with free-running index. + * __u16 used_flags; + * __u16 used_idx; + * struct vring_used_elem used[num]; + * }; + */ +static inline void vring_init(struct vring *vr, unsigned int num, void *p) +{ + vr->num = num; + vr->desc = p; + vr->avail = p + num*sizeof(struct vring); + vr->used = p + (num+1)*(sizeof(struct vring) + sizeof(__u16)); +} + +static inline unsigned vring_size(unsigned int num) +{ + return (num + 1) * (sizeof(struct vring_desc) + sizeof(__u16)) + + sizeof(__u32) + num * sizeof(struct vring_used_elem); +} + +#ifdef __KERNEL__ +#include <linux/irqreturn.h> +struct virtio_device; +struct virtqueue; + +struct virtqueue *vring_new_virtqueue(unsigned int num, + struct virtio_device *vdev, + void *pages, + void (*notify)(struct virtqueue *vq), + bool (*callback)(struct virtqueue *vq)); +void vring_del_virtqueue(struct virtqueue *vq); + +irqreturn_t vring_interrupt(int irq, void *_vq); +#endif /* __KERNEL__ */ +#endif /* _LINUX_VIRTIO_RING_H */ |