linux/net/9p/trans_xen.c
Stefano Stabellini 36f9967531 9p/xen: increase XEN_9PFS_RING_ORDER
Increase XEN_9PFS_RING_ORDER to 9 for performance reason. Order 9 is the
max allowed by the protocol.

We can't assume that all backends will support order 9. The xenstore
property max-ring-page-order specifies the max order supported by the
backend. We'll use max-ring-page-order for the size of the ring.

This means that the size of the ring is not static
(XEN_FLEX_RING_SIZE(9)) anymore. Change XEN_9PFS_RING_SIZE to take an
argument and base the calculation on the order chosen at setup time.

Finally, modify p9_xen_trans.maxsize to be divided by 4 compared to the
original value. We need to divide it by 2 because we have two rings
coming off the same order allocation: the in and out rings. This was a
mistake in the original code. Also divide it further by 2 because we
don't want a single request/reply to fill up the entire ring. There can
be multiple requests/replies outstanding at any given time and if we use
the full ring with one, we risk forcing the backend to wait for the
client to read back more replies before continuing, which is not
performant.

Link: http://lkml.kernel.org/r/20200521193242.15953-1-sstabellini@kernel.org
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
2020-06-02 08:00:39 +02:00

566 lines
14 KiB
C

/*
* linux/fs/9p/trans_xen
*
* Xen transport layer.
*
* Copyright (C) 2017 by Stefano Stabellini <stefano@aporeto.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation; or, when distributed
* separately from the Linux kernel or incorporated into other
* software packages, subject to the following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this source file (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify,
* merge, publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include <xen/events.h>
#include <xen/grant_table.h>
#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/interface/io/9pfs.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>
#include <net/9p/transport.h>
#define XEN_9PFS_NUM_RINGS 2
#define XEN_9PFS_RING_ORDER 9
#define XEN_9PFS_RING_SIZE(ring) XEN_FLEX_RING_SIZE(ring->intf->ring_order)
struct xen_9pfs_header {
uint32_t size;
uint8_t id;
uint16_t tag;
/* uint8_t sdata[]; */
} __attribute__((packed));
/* One per ring, more than one per 9pfs share */
struct xen_9pfs_dataring {
struct xen_9pfs_front_priv *priv;
struct xen_9pfs_data_intf *intf;
grant_ref_t ref;
int evtchn;
int irq;
/* protect a ring from concurrent accesses */
spinlock_t lock;
struct xen_9pfs_data data;
wait_queue_head_t wq;
struct work_struct work;
};
/* One per 9pfs share */
struct xen_9pfs_front_priv {
struct list_head list;
struct xenbus_device *dev;
char *tag;
struct p9_client *client;
int num_rings;
struct xen_9pfs_dataring *rings;
};
static LIST_HEAD(xen_9pfs_devs);
static DEFINE_RWLOCK(xen_9pfs_lock);
/* We don't currently allow canceling of requests */
static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
{
return 1;
}
static int p9_xen_create(struct p9_client *client, const char *addr, char *args)
{
struct xen_9pfs_front_priv *priv;
if (addr == NULL)
return -EINVAL;
read_lock(&xen_9pfs_lock);
list_for_each_entry(priv, &xen_9pfs_devs, list) {
if (!strcmp(priv->tag, addr)) {
priv->client = client;
read_unlock(&xen_9pfs_lock);
return 0;
}
}
read_unlock(&xen_9pfs_lock);
return -EINVAL;
}
static void p9_xen_close(struct p9_client *client)
{
struct xen_9pfs_front_priv *priv;
read_lock(&xen_9pfs_lock);
list_for_each_entry(priv, &xen_9pfs_devs, list) {
if (priv->client == client) {
priv->client = NULL;
read_unlock(&xen_9pfs_lock);
return;
}
}
read_unlock(&xen_9pfs_lock);
}
static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
{
RING_IDX cons, prod;
cons = ring->intf->out_cons;
prod = ring->intf->out_prod;
virt_mb();
return XEN_9PFS_RING_SIZE(ring) -
xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) >= size;
}
static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
{
struct xen_9pfs_front_priv *priv = NULL;
RING_IDX cons, prod, masked_cons, masked_prod;
unsigned long flags;
u32 size = p9_req->tc.size;
struct xen_9pfs_dataring *ring;
int num;
read_lock(&xen_9pfs_lock);
list_for_each_entry(priv, &xen_9pfs_devs, list) {
if (priv->client == client)
break;
}
read_unlock(&xen_9pfs_lock);
if (!priv || priv->client != client)
return -EINVAL;
num = p9_req->tc.tag % priv->num_rings;
ring = &priv->rings[num];
again:
while (wait_event_killable(ring->wq,
p9_xen_write_todo(ring, size)) != 0)
;
spin_lock_irqsave(&ring->lock, flags);
cons = ring->intf->out_cons;
prod = ring->intf->out_prod;
virt_mb();
if (XEN_9PFS_RING_SIZE(ring) -
xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) < size) {
spin_unlock_irqrestore(&ring->lock, flags);
goto again;
}
masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
xen_9pfs_write_packet(ring->data.out, p9_req->tc.sdata, size,
&masked_prod, masked_cons,
XEN_9PFS_RING_SIZE(ring));
p9_req->status = REQ_STATUS_SENT;
virt_wmb(); /* write ring before updating pointer */
prod += size;
ring->intf->out_prod = prod;
spin_unlock_irqrestore(&ring->lock, flags);
notify_remote_via_irq(ring->irq);
p9_req_put(p9_req);
return 0;
}
static void p9_xen_response(struct work_struct *work)
{
struct xen_9pfs_front_priv *priv;
struct xen_9pfs_dataring *ring;
RING_IDX cons, prod, masked_cons, masked_prod;
struct xen_9pfs_header h;
struct p9_req_t *req;
int status;
ring = container_of(work, struct xen_9pfs_dataring, work);
priv = ring->priv;
while (1) {
cons = ring->intf->in_cons;
prod = ring->intf->in_prod;
virt_rmb();
if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) <
sizeof(h)) {
notify_remote_via_irq(ring->irq);
return;
}
masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
/* First, read just the header */
xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
masked_prod, &masked_cons,
XEN_9PFS_RING_SIZE(ring));
req = p9_tag_lookup(priv->client, h.tag);
if (!req || req->status != REQ_STATUS_SENT) {
dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
cons += h.size;
virt_mb();
ring->intf->in_cons = cons;
continue;
}
memcpy(&req->rc, &h, sizeof(h));
req->rc.offset = 0;
masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
/* Then, read the whole packet (including the header) */
xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
masked_prod, &masked_cons,
XEN_9PFS_RING_SIZE(ring));
virt_mb();
cons += h.size;
ring->intf->in_cons = cons;
status = (req->status != REQ_STATUS_ERROR) ?
REQ_STATUS_RCVD : REQ_STATUS_ERROR;
p9_client_cb(priv->client, req, status);
}
}
static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
{
struct xen_9pfs_dataring *ring = r;
if (!ring || !ring->priv->client) {
/* ignore spurious interrupt */
return IRQ_HANDLED;
}
wake_up_interruptible(&ring->wq);
schedule_work(&ring->work);
return IRQ_HANDLED;
}
static struct p9_trans_module p9_xen_trans = {
.name = "xen",
.maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
.def = 1,
.create = p9_xen_create,
.close = p9_xen_close,
.request = p9_xen_request,
.cancel = p9_xen_cancel,
.owner = THIS_MODULE,
};
static const struct xenbus_device_id xen_9pfs_front_ids[] = {
{ "9pfs" },
{ "" }
};
static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
{
int i, j;
write_lock(&xen_9pfs_lock);
list_del(&priv->list);
write_unlock(&xen_9pfs_lock);
for (i = 0; i < priv->num_rings; i++) {
if (!priv->rings[i].intf)
break;
if (priv->rings[i].irq > 0)
unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
if (priv->rings[i].data.in) {
for (j = 0;
j < (1 << priv->rings[i].intf->ring_order);
j++) {
grant_ref_t ref;
ref = priv->rings[i].intf->ref[j];
gnttab_end_foreign_access(ref, 0, 0);
}
free_pages((unsigned long)priv->rings[i].data.in,
priv->rings[i].intf->ring_order -
(PAGE_SHIFT - XEN_PAGE_SHIFT));
}
gnttab_end_foreign_access(priv->rings[i].ref, 0, 0);
free_page((unsigned long)priv->rings[i].intf);
}
kfree(priv->rings);
kfree(priv->tag);
kfree(priv);
}
static int xen_9pfs_front_remove(struct xenbus_device *dev)
{
struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
dev_set_drvdata(&dev->dev, NULL);
xen_9pfs_front_free(priv);
return 0;
}
static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
struct xen_9pfs_dataring *ring,
unsigned int order)
{
int i = 0;
int ret = -ENOMEM;
void *bytes = NULL;
init_waitqueue_head(&ring->wq);
spin_lock_init(&ring->lock);
INIT_WORK(&ring->work, p9_xen_response);
ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
if (!ring->intf)
return ret;
ret = gnttab_grant_foreign_access(dev->otherend_id,
virt_to_gfn(ring->intf), 0);
if (ret < 0)
goto out;
ring->ref = ret;
bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
order - (PAGE_SHIFT - XEN_PAGE_SHIFT));
if (!bytes) {
ret = -ENOMEM;
goto out;
}
for (; i < (1 << order); i++) {
ret = gnttab_grant_foreign_access(
dev->otherend_id, virt_to_gfn(bytes) + i, 0);
if (ret < 0)
goto out;
ring->intf->ref[i] = ret;
}
ring->intf->ring_order = order;
ring->data.in = bytes;
ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
if (ret)
goto out;
ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
xen_9pfs_front_event_handler,
0, "xen_9pfs-frontend", ring);
if (ring->irq >= 0)
return 0;
xenbus_free_evtchn(dev, ring->evtchn);
ret = ring->irq;
out:
if (bytes) {
for (i--; i >= 0; i--)
gnttab_end_foreign_access(ring->intf->ref[i], 0, 0);
free_pages((unsigned long)bytes,
ring->intf->ring_order -
(PAGE_SHIFT - XEN_PAGE_SHIFT));
}
gnttab_end_foreign_access(ring->ref, 0, 0);
free_page((unsigned long)ring->intf);
return ret;
}
static int xen_9pfs_front_probe(struct xenbus_device *dev,
const struct xenbus_device_id *id)
{
int ret, i;
struct xenbus_transaction xbt;
struct xen_9pfs_front_priv *priv = NULL;
char *versions;
unsigned int max_rings, max_ring_order, len = 0;
versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
if (IS_ERR(versions))
return PTR_ERR(versions);
if (strcmp(versions, "1")) {
kfree(versions);
return -EINVAL;
}
kfree(versions);
max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
if (max_rings < XEN_9PFS_NUM_RINGS)
return -EINVAL;
max_ring_order = xenbus_read_unsigned(dev->otherend,
"max-ring-page-order", 0);
if (max_ring_order > XEN_9PFS_RING_ORDER)
max_ring_order = XEN_9PFS_RING_ORDER;
if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
priv->dev = dev;
priv->num_rings = XEN_9PFS_NUM_RINGS;
priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
GFP_KERNEL);
if (!priv->rings) {
kfree(priv);
return -ENOMEM;
}
for (i = 0; i < priv->num_rings; i++) {
priv->rings[i].priv = priv;
ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
max_ring_order);
if (ret < 0)
goto error;
}
again:
ret = xenbus_transaction_start(&xbt);
if (ret) {
xenbus_dev_fatal(dev, ret, "starting transaction");
goto error;
}
ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
if (ret)
goto error_xenbus;
ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
priv->num_rings);
if (ret)
goto error_xenbus;
for (i = 0; i < priv->num_rings; i++) {
char str[16];
BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
sprintf(str, "ring-ref%u", i);
ret = xenbus_printf(xbt, dev->nodename, str, "%d",
priv->rings[i].ref);
if (ret)
goto error_xenbus;
sprintf(str, "event-channel-%u", i);
ret = xenbus_printf(xbt, dev->nodename, str, "%u",
priv->rings[i].evtchn);
if (ret)
goto error_xenbus;
}
priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
if (IS_ERR(priv->tag)) {
ret = PTR_ERR(priv->tag);
goto error_xenbus;
}
ret = xenbus_transaction_end(xbt, 0);
if (ret) {
if (ret == -EAGAIN)
goto again;
xenbus_dev_fatal(dev, ret, "completing transaction");
goto error;
}
write_lock(&xen_9pfs_lock);
list_add_tail(&priv->list, &xen_9pfs_devs);
write_unlock(&xen_9pfs_lock);
dev_set_drvdata(&dev->dev, priv);
xenbus_switch_state(dev, XenbusStateInitialised);
return 0;
error_xenbus:
xenbus_transaction_end(xbt, 1);
xenbus_dev_fatal(dev, ret, "writing xenstore");
error:
dev_set_drvdata(&dev->dev, NULL);
xen_9pfs_front_free(priv);
return ret;
}
static int xen_9pfs_front_resume(struct xenbus_device *dev)
{
dev_warn(&dev->dev, "suspend/resume unsupported\n");
return 0;
}
static void xen_9pfs_front_changed(struct xenbus_device *dev,
enum xenbus_state backend_state)
{
switch (backend_state) {
case XenbusStateReconfiguring:
case XenbusStateReconfigured:
case XenbusStateInitialising:
case XenbusStateInitialised:
case XenbusStateUnknown:
break;
case XenbusStateInitWait:
break;
case XenbusStateConnected:
xenbus_switch_state(dev, XenbusStateConnected);
break;
case XenbusStateClosed:
if (dev->state == XenbusStateClosed)
break;
/* fall through - Missed the backend's CLOSING state */
case XenbusStateClosing:
xenbus_frontend_closed(dev);
break;
}
}
static struct xenbus_driver xen_9pfs_front_driver = {
.ids = xen_9pfs_front_ids,
.probe = xen_9pfs_front_probe,
.remove = xen_9pfs_front_remove,
.resume = xen_9pfs_front_resume,
.otherend_changed = xen_9pfs_front_changed,
};
static int p9_trans_xen_init(void)
{
int rc;
if (!xen_domain())
return -ENODEV;
pr_info("Initialising Xen transport for 9pfs\n");
v9fs_register_trans(&p9_xen_trans);
rc = xenbus_register_frontend(&xen_9pfs_front_driver);
if (rc)
v9fs_unregister_trans(&p9_xen_trans);
return rc;
}
module_init(p9_trans_xen_init);
static void p9_trans_xen_exit(void)
{
v9fs_unregister_trans(&p9_xen_trans);
return xenbus_unregister_driver(&xen_9pfs_front_driver);
}
module_exit(p9_trans_xen_exit);
MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
MODULE_DESCRIPTION("Xen Transport for 9P");
MODULE_LICENSE("GPL");