vringh: host-side implementation of virtio rings.

Getting use of virtio rings correct is tricky, and a recent patch saw
an implementation of in-kernel rings (as separate from userspace).

This abstracts the business of dealing with the virtio ring layout
from the access (userspace or direct); to do this, we use function
pointers, which gcc inlines correctly.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Rusty Russell 2013-03-20 13:50:14 +10:30
parent 61d0b5a4b2
commit f87d0fbb57
6 changed files with 1215 additions and 1 deletions

View File

@ -123,7 +123,7 @@ obj-$(CONFIG_PPC_PS3) += ps3/
obj-$(CONFIG_OF) += of/
obj-$(CONFIG_SSB) += ssb/
obj-$(CONFIG_BCMA) += bcma/
obj-$(CONFIG_VHOST_NET) += vhost/
obj-$(CONFIG_VHOST_RING) += vhost/
obj-$(CONFIG_VLYNQ) += vlynq/
obj-$(CONFIG_STAGING) += staging/
obj-y += platform/

View File

@ -1,6 +1,7 @@
config VHOST_NET
tristate "Host kernel accelerator for virtio net"
depends on NET && EVENTFD && (TUN || !TUN) && (MACVTAP || !MACVTAP)
select VHOST_RING
---help---
This kernel module can be loaded in host kernel to accelerate
guest networking with virtio_net. Not to be confused with virtio_net
@ -12,3 +13,10 @@ config VHOST_NET
if STAGING
source "drivers/vhost/Kconfig.tcm"
endif
config VHOST_RING
tristate
---help---
This option is selected by any driver which needs to access
the host side of a virtio ring.

View File

@ -1,6 +1,7 @@
config TCM_VHOST
tristate "TCM_VHOST fabric module"
depends on TARGET_CORE && EVENTFD && m
select VHOST_RING
default n
---help---
Say M here to enable the TCM_VHOST fabric module for use with virtio-scsi guests

View File

@ -2,3 +2,5 @@ obj-$(CONFIG_VHOST_NET) += vhost_net.o
vhost_net-y := vhost.o net.o
obj-$(CONFIG_TCM_VHOST) += tcm_vhost.o
obj-$(CONFIG_VHOST_RING) += vringh.o

1007
drivers/vhost/vringh.c Normal file

File diff suppressed because it is too large Load Diff

196
include/linux/vringh.h Normal file
View File

@ -0,0 +1,196 @@
/*
* Linux host-side vring helpers; for when the kernel needs to access
* someone else's vring.
*
* Copyright IBM Corporation, 2013.
* Parts taken from drivers/vhost/vhost.c Copyright 2009 Red Hat, Inc.
*
* 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Written by: Rusty Russell <rusty@rustcorp.com.au>
*/
#ifndef _LINUX_VRINGH_H
#define _LINUX_VRINGH_H
#include <uapi/linux/virtio_ring.h>
#include <linux/uio.h>
#include <linux/slab.h>
#include <asm/barrier.h>
/* virtio_ring with information needed for host access. */
struct vringh {
/* Guest publishes used event idx (note: we always do). */
bool event_indices;
/* Can we get away with weak barriers? */
bool weak_barriers;
/* Last available index we saw (ie. where we're up to). */
u16 last_avail_idx;
/* Last index we used. */
u16 last_used_idx;
/* How many descriptors we've completed since last need_notify(). */
u32 completed;
/* The vring (note: it may contain user pointers!) */
struct vring vring;
};
/* The memory the vring can access, and what offset to apply. */
struct vringh_range {
u64 start, end_incl;
u64 offset;
};
/**
* struct vringh_iov - iovec mangler.
*
* Mangles iovec in place, and restores it.
* Remaining data is iov + i, of used - i elements.
*/
struct vringh_iov {
struct iovec *iov;
size_t consumed; /* Within iov[i] */
unsigned i, used, max_num;
};
/**
* struct vringh_iov - kvec mangler.
*
* Mangles kvec in place, and restores it.
* Remaining data is iov + i, of used - i elements.
*/
struct vringh_kiov {
struct kvec *iov;
size_t consumed; /* Within iov[i] */
unsigned i, used, max_num;
};
/* Flag on max_num to indicate we're kmalloced. */
#define VRINGH_IOV_ALLOCATED 0x8000000
/* Helpers for userspace vrings. */
int vringh_init_user(struct vringh *vrh, u32 features,
unsigned int num, bool weak_barriers,
struct vring_desc __user *desc,
struct vring_avail __user *avail,
struct vring_used __user *used);
static inline void vringh_iov_init(struct vringh_iov *iov,
struct iovec *iovec, unsigned num)
{
iov->used = iov->i = 0;
iov->consumed = 0;
iov->max_num = num;
iov->iov = iovec;
}
static inline void vringh_iov_reset(struct vringh_iov *iov)
{
iov->iov[iov->i].iov_len += iov->consumed;
iov->iov[iov->i].iov_base -= iov->consumed;
iov->consumed = 0;
iov->i = 0;
}
static inline void vringh_iov_cleanup(struct vringh_iov *iov)
{
if (iov->max_num & VRINGH_IOV_ALLOCATED)
kfree(iov->iov);
iov->max_num = iov->used = iov->i = iov->consumed = 0;
iov->iov = NULL;
}
/* Convert a descriptor into iovecs. */
int vringh_getdesc_user(struct vringh *vrh,
struct vringh_iov *riov,
struct vringh_iov *wiov,
bool (*getrange)(struct vringh *vrh,
u64 addr, struct vringh_range *r),
u16 *head);
/* Copy bytes from readable vsg, consuming it (and incrementing wiov->i). */
ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len);
/* Copy bytes into writable vsg, consuming it (and incrementing wiov->i). */
ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
const void *src, size_t len);
/* Mark a descriptor as used. */
int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
int vringh_complete_multi_user(struct vringh *vrh,
const struct vring_used_elem used[],
unsigned num_used);
/* Pretend we've never seen descriptor (for easy error handling). */
void vringh_abandon_user(struct vringh *vrh, unsigned int num);
/* Do we need to fire the eventfd to notify the other side? */
int vringh_need_notify_user(struct vringh *vrh);
bool vringh_notify_enable_user(struct vringh *vrh);
void vringh_notify_disable_user(struct vringh *vrh);
/* Helpers for kernelspace vrings. */
int vringh_init_kern(struct vringh *vrh, u32 features,
unsigned int num, bool weak_barriers,
struct vring_desc *desc,
struct vring_avail *avail,
struct vring_used *used);
static inline void vringh_kiov_init(struct vringh_kiov *kiov,
struct kvec *kvec, unsigned num)
{
kiov->used = kiov->i = 0;
kiov->consumed = 0;
kiov->max_num = num;
kiov->iov = kvec;
}
static inline void vringh_kiov_reset(struct vringh_kiov *kiov)
{
kiov->iov[kiov->i].iov_len += kiov->consumed;
kiov->iov[kiov->i].iov_base -= kiov->consumed;
kiov->consumed = 0;
kiov->i = 0;
}
static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov)
{
if (kiov->max_num & VRINGH_IOV_ALLOCATED)
kfree(kiov->iov);
kiov->max_num = kiov->used = kiov->i = kiov->consumed = 0;
kiov->iov = NULL;
}
int vringh_getdesc_kern(struct vringh *vrh,
struct vringh_kiov *riov,
struct vringh_kiov *wiov,
u16 *head,
gfp_t gfp);
ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
const void *src, size_t len);
void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
bool vringh_notify_enable_kern(struct vringh *vrh);
void vringh_notify_disable_kern(struct vringh *vrh);
int vringh_need_notify_kern(struct vringh *vrh);
#endif /* _LINUX_VRINGH_H */