mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-11-25 18:50:55 +07:00
7b21e34fd1
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>
183 lines
6.4 KiB
C
183 lines
6.4 KiB
C
#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.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
* 3. Neither the name of IBM nor the names of its contributors
|
|
* may be used to endorse or promote products derived from this software
|
|
* without specific prior written permission.
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*
|
|
* 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 the buffer contains a list of buffer descriptors. */
|
|
#define VRING_DESC_F_INDIRECT 4
|
|
|
|
/* The Host uses this in used->flags to advise the Guest: don't kick me when
|
|
* you add a buffer. It's unreliable, so it's simply an optimization. Guest
|
|
* will still kick if it's out of buffers. */
|
|
#define VRING_USED_F_NO_NOTIFY 1
|
|
/* The Guest uses this in avail->flags to advise the Host: don't interrupt me
|
|
* when you consume a buffer. It's unreliable, so it's simply an
|
|
* optimization. */
|
|
#define VRING_AVAIL_F_NO_INTERRUPT 1
|
|
|
|
/* We support indirect buffer descriptors */
|
|
#define VIRTIO_RING_F_INDIRECT_DESC 28
|
|
|
|
/* The Guest publishes the used index for which it expects an interrupt
|
|
* at the end of the avail ring. Host should ignore the avail->flags field. */
|
|
/* The Host publishes the avail index for which it expects a kick
|
|
* at the end of the used ring. Guest should ignore the used->flags field. */
|
|
#define VIRTIO_RING_F_EVENT_IDX 29
|
|
|
|
/* 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. We assume num is a power of 2.
|
|
*
|
|
* 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];
|
|
* __u16 used_event_idx;
|
|
*
|
|
* // Padding to the next align boundary.
|
|
* char pad[];
|
|
*
|
|
* // A ring of used descriptor heads with free-running index.
|
|
* __u16 used_flags;
|
|
* __u16 used_idx;
|
|
* struct vring_used_elem used[num];
|
|
* __u16 avail_event_idx;
|
|
* };
|
|
*/
|
|
/* We publish the used event index at the end of the available ring, and vice
|
|
* versa. They are at the end for backwards compatibility. */
|
|
#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
|
|
#define vring_avail_event(vr) (*(__u16 *)&(vr)->used->ring[(vr)->num])
|
|
|
|
static inline void vring_init(struct vring *vr, unsigned int num, void *p,
|
|
unsigned long align)
|
|
{
|
|
vr->num = num;
|
|
vr->desc = p;
|
|
vr->avail = p + num*sizeof(struct vring_desc);
|
|
vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + sizeof(__u16)
|
|
+ align-1) & ~(align - 1));
|
|
}
|
|
|
|
static inline unsigned vring_size(unsigned int num, unsigned long align)
|
|
{
|
|
return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (3 + num)
|
|
+ align - 1) & ~(align - 1))
|
|
+ sizeof(__u16) * 3 + sizeof(struct vring_used_elem) * num;
|
|
}
|
|
|
|
/* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */
|
|
/* Assuming a given event_idx value from the other size, if
|
|
* we have just incremented index from old to new_idx,
|
|
* should we trigger an event? */
|
|
static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old)
|
|
{
|
|
/* Note: 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.
|
|
* Note also that req_event and req_prod in Xen start at 1,
|
|
* event indexes in virtio start at 0. */
|
|
return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);
|
|
}
|
|
|
|
#ifdef __KERNEL__
|
|
#include <linux/irqreturn.h>
|
|
struct virtio_device;
|
|
struct virtqueue;
|
|
|
|
struct virtqueue *vring_new_virtqueue(unsigned int num,
|
|
unsigned int vring_align,
|
|
struct virtio_device *vdev,
|
|
bool weak_barriers,
|
|
void *pages,
|
|
void (*notify)(struct virtqueue *vq),
|
|
void (*callback)(struct virtqueue *vq),
|
|
const char *name);
|
|
void vring_del_virtqueue(struct virtqueue *vq);
|
|
/* Filter out transport-specific feature bits. */
|
|
void vring_transport_features(struct virtio_device *vdev);
|
|
|
|
irqreturn_t vring_interrupt(int irq, void *_vq);
|
|
#endif /* __KERNEL__ */
|
|
#endif /* _LINUX_VIRTIO_RING_H */
|