Re: [PATCH RFC v6 02/11] vhost: use batched get_vq_desc version
On 2020/6/11 下午5:06, Michael S. Tsirkin wrote:
On Thu, Jun 11, 2020 at 11:02:57AM +0800, Jason Wang wrote:
On 2020/6/10 下午7:05, Michael S. Tsirkin wrote:
+EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
/* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
{
+ unfetch_descs(vq);
vq->last_avail_idx -= n;
So unfetch_descs() has decreased last_avail_idx.
Can we fix this by letting unfetch_descs() return the number and then we can
do:
int d = unfetch_descs(vq);
vq->last_avail_idx -= (n > d) ? n - d: 0;
Thanks
That's intentional I think - we need both.
Yes, but:
Unfetch_descs drops the descriptors in the cache that were
*not returned to caller* through get_vq_desc.
vhost_discard_vq_desc drops the ones that were returned through get_vq_desc.
Did I miss anything?
We could count some descriptors twice, consider the case e.g we only cache
on descriptor:
fetch_descs()
fetch_buf()
last_avail_idx++;
Then we want do discard it:
vhost_discard_avail_buf(1)
unfetch_descs()
last_avail_idx--;
last_avail_idx -= 1;
Thanks
I don't think that happens. vhost_discard_avail_buf(1) is only called
after get vhost_get_avail_buf. vhost_get_avail_buf increments
first_desc. unfetch_descs only counts from first_desc to ndescs.
If I'm wrong, could you show values of first_desc and ndescs in this
scenario?
You're right, fetch_descriptor could not be called directly from the
device code.
Thanks
___
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH RFC v6 02/11] vhost: use batched get_vq_desc version
On Thu, Jun 11, 2020 at 11:02:57AM +0800, Jason Wang wrote:
>
> On 2020/6/10 下午7:05, Michael S. Tsirkin wrote:
> > > > +EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
> > > >/* Reverse the effect of vhost_get_vq_desc. Useful for error
> > > > handling. */
> > > >void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
> > > >{
> > > > + unfetch_descs(vq);
> > > > vq->last_avail_idx -= n;
> > > So unfetch_descs() has decreased last_avail_idx.
> > > Can we fix this by letting unfetch_descs() return the number and then we
> > > can
> > > do:
> > >
> > > int d = unfetch_descs(vq);
> > > vq->last_avail_idx -= (n > d) ? n - d: 0;
> > >
> > > Thanks
> > That's intentional I think - we need both.
>
>
> Yes, but:
>
>
> >
> > Unfetch_descs drops the descriptors in the cache that were
> > *not returned to caller* through get_vq_desc.
> >
> > vhost_discard_vq_desc drops the ones that were returned through get_vq_desc.
> >
> > Did I miss anything?
>
> We could count some descriptors twice, consider the case e.g we only cache
> on descriptor:
>
> fetch_descs()
> fetch_buf()
> last_avail_idx++;
>
> Then we want do discard it:
> vhost_discard_avail_buf(1)
> unfetch_descs()
> last_avail_idx--;
> last_avail_idx -= 1;
>
> Thanks
I don't think that happens. vhost_discard_avail_buf(1) is only called
after get vhost_get_avail_buf. vhost_get_avail_buf increments
first_desc. unfetch_descs only counts from first_desc to ndescs.
If I'm wrong, could you show values of first_desc and ndescs in this
scenario?
--
MST
___
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH RFC v6 02/11] vhost: use batched get_vq_desc version
On 2020/6/10 下午7:05, Michael S. Tsirkin wrote:
+EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
/* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
{
+ unfetch_descs(vq);
vq->last_avail_idx -= n;
So unfetch_descs() has decreased last_avail_idx.
Can we fix this by letting unfetch_descs() return the number and then we can
do:
int d = unfetch_descs(vq);
vq->last_avail_idx -= (n > d) ? n - d: 0;
Thanks
That's intentional I think - we need both.
Yes, but:
Unfetch_descs drops the descriptors in the cache that were
*not returned to caller* through get_vq_desc.
vhost_discard_vq_desc drops the ones that were returned through get_vq_desc.
Did I miss anything?
We could count some descriptors twice, consider the case e.g we only
cache on descriptor:
fetch_descs()
fetch_buf()
last_avail_idx++;
Then we want do discard it:
vhost_discard_avail_buf(1)
unfetch_descs()
last_avail_idx--;
last_avail_idx -= 1;
Thanks
___
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH RFC v6 02/11] vhost: use batched get_vq_desc version
On Wed, Jun 10, 2020 at 11:14:49AM +0800, Jason Wang wrote:
>
> On 2020/6/8 下午8:52, Michael S. Tsirkin wrote:
> > As testing shows no performance change, switch to that now.
> >
> > Signed-off-by: Michael S. Tsirkin
> > Signed-off-by: Eugenio Pérez
> > Link: https://lore.kernel.org/r/20200401183118.8334-3-epere...@redhat.com
> > Signed-off-by: Michael S. Tsirkin
> > ---
> > drivers/vhost/test.c | 2 +-
> > drivers/vhost/vhost.c | 318 --
> > drivers/vhost/vhost.h | 7 +-
> > 3 files changed, 65 insertions(+), 262 deletions(-)
> >
> > diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
> > index 0466921f4772..7d69778aaa26 100644
> > --- a/drivers/vhost/test.c
> > +++ b/drivers/vhost/test.c
> > @@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struct
> > file *f)
> > dev = >dev;
> > vqs[VHOST_TEST_VQ] = >vqs[VHOST_TEST_VQ];
> > n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick;
> > - vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV,
> > + vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64,
> >VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, true, NULL);
> > f->private_data = n;
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index 180b7b58c76b..41d6b132c234 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -304,6 +304,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
> > {
> > vq->num = 1;
> > vq->ndescs = 0;
> > + vq->first_desc = 0;
> > vq->desc = NULL;
> > vq->avail = NULL;
> > vq->used = NULL;
> > @@ -372,6 +373,11 @@ static int vhost_worker(void *data)
> > return 0;
> > }
> > +static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq)
> > +{
> > + return vq->max_descs - UIO_MAXIOV;
> > +}
> > +
> > static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
> > {
> > kfree(vq->descs);
> > @@ -394,6 +400,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev
> > *dev)
> > for (i = 0; i < dev->nvqs; ++i) {
> > vq = dev->vqs[i];
> > vq->max_descs = dev->iov_limit;
> > + if (vhost_vq_num_batch_descs(vq) < 0) {
> > + return -EINVAL;
> > + }
> > vq->descs = kmalloc_array(vq->max_descs,
> > sizeof(*vq->descs),
> > GFP_KERNEL);
> > @@ -1610,6 +1619,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned
> > int ioctl, void __user *arg
> > vq->last_avail_idx = s.num;
> > /* Forget the cached index value. */
> > vq->avail_idx = vq->last_avail_idx;
> > + vq->ndescs = vq->first_desc = 0;
> > break;
> > case VHOST_GET_VRING_BASE:
> > s.index = idx;
> > @@ -2078,253 +2088,6 @@ static unsigned next_desc(struct vhost_virtqueue
> > *vq, struct vring_desc *desc)
> > return next;
> > }
> > -static int get_indirect(struct vhost_virtqueue *vq,
> > - struct iovec iov[], unsigned int iov_size,
> > - unsigned int *out_num, unsigned int *in_num,
> > - struct vhost_log *log, unsigned int *log_num,
> > - struct vring_desc *indirect)
> > -{
> > - struct vring_desc desc;
> > - unsigned int i = 0, count, found = 0;
> > - u32 len = vhost32_to_cpu(vq, indirect->len);
> > - struct iov_iter from;
> > - int ret, access;
> > -
> > - /* Sanity check */
> > - if (unlikely(len % sizeof desc)) {
> > - vq_err(vq, "Invalid length in indirect descriptor: "
> > - "len 0x%llx not multiple of 0x%zx\n",
> > - (unsigned long long)len,
> > - sizeof desc);
> > - return -EINVAL;
> > - }
> > -
> > - ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len,
> > vq->indirect,
> > -UIO_MAXIOV, VHOST_ACCESS_RO);
> > - if (unlikely(ret < 0)) {
> > - if (ret != -EAGAIN)
> > - vq_err(vq, "Translation failure %d in indirect.\n",
> > ret);
> > - return ret;
> > - }
> > - iov_iter_init(, READ, vq->indirect, ret, len);
> > -
> > - /* We will use the result as an address to read from, so most
> > -* architectures only need a compiler barrier here. */
> > - read_barrier_depends();
> > -
> > - count = len / sizeof desc;
> > - /* Buffers are chained via a 16 bit next field, so
> > -* we can have at most 2^16 of these. */
> > - if (unlikely(count > USHRT_MAX + 1)) {
> > - vq_err(vq, "Indirect buffer length too big: %d\n",
> > - indirect->len);
> > - return -E2BIG;
> > - }
> > -
> > - do {
> > - unsigned iov_count = *in_num + *out_num;
> > - if (unlikely(++found > count)) {
> > - vq_err(vq, "Loop detected: last one at %u "
> > - "indirect size %u\n",
> > -
Re: [PATCH RFC v6 02/11] vhost: use batched get_vq_desc version
On 2020/6/8 下午8:52, Michael S. Tsirkin wrote:
As testing shows no performance change, switch to that now.
Signed-off-by: Michael S. Tsirkin
Signed-off-by: Eugenio Pérez
Link: https://lore.kernel.org/r/20200401183118.8334-3-epere...@redhat.com
Signed-off-by: Michael S. Tsirkin
---
drivers/vhost/test.c | 2 +-
drivers/vhost/vhost.c | 318 --
drivers/vhost/vhost.h | 7 +-
3 files changed, 65 insertions(+), 262 deletions(-)
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index 0466921f4772..7d69778aaa26 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struct file
*f)
dev = >dev;
vqs[VHOST_TEST_VQ] = >vqs[VHOST_TEST_VQ];
n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick;
- vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV,
+ vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64,
VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, true, NULL);
f->private_data = n;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 180b7b58c76b..41d6b132c234 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -304,6 +304,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
{
vq->num = 1;
vq->ndescs = 0;
+ vq->first_desc = 0;
vq->desc = NULL;
vq->avail = NULL;
vq->used = NULL;
@@ -372,6 +373,11 @@ static int vhost_worker(void *data)
return 0;
}
+static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq)
+{
+ return vq->max_descs - UIO_MAXIOV;
+}
+
static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
{
kfree(vq->descs);
@@ -394,6 +400,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
for (i = 0; i < dev->nvqs; ++i) {
vq = dev->vqs[i];
vq->max_descs = dev->iov_limit;
+ if (vhost_vq_num_batch_descs(vq) < 0) {
+ return -EINVAL;
+ }
vq->descs = kmalloc_array(vq->max_descs,
sizeof(*vq->descs),
GFP_KERNEL);
@@ -1610,6 +1619,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int
ioctl, void __user *arg
vq->last_avail_idx = s.num;
/* Forget the cached index value. */
vq->avail_idx = vq->last_avail_idx;
+ vq->ndescs = vq->first_desc = 0;
break;
case VHOST_GET_VRING_BASE:
s.index = idx;
@@ -2078,253 +2088,6 @@ static unsigned next_desc(struct vhost_virtqueue *vq,
struct vring_desc *desc)
return next;
}
-static int get_indirect(struct vhost_virtqueue *vq,
- struct iovec iov[], unsigned int iov_size,
- unsigned int *out_num, unsigned int *in_num,
- struct vhost_log *log, unsigned int *log_num,
- struct vring_desc *indirect)
-{
- struct vring_desc desc;
- unsigned int i = 0, count, found = 0;
- u32 len = vhost32_to_cpu(vq, indirect->len);
- struct iov_iter from;
- int ret, access;
-
- /* Sanity check */
- if (unlikely(len % sizeof desc)) {
- vq_err(vq, "Invalid length in indirect descriptor: "
- "len 0x%llx not multiple of 0x%zx\n",
- (unsigned long long)len,
- sizeof desc);
- return -EINVAL;
- }
-
- ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len,
vq->indirect,
-UIO_MAXIOV, VHOST_ACCESS_RO);
- if (unlikely(ret < 0)) {
- if (ret != -EAGAIN)
- vq_err(vq, "Translation failure %d in indirect.\n",
ret);
- return ret;
- }
- iov_iter_init(, READ, vq->indirect, ret, len);
-
- /* We will use the result as an address to read from, so most
-* architectures only need a compiler barrier here. */
- read_barrier_depends();
-
- count = len / sizeof desc;
- /* Buffers are chained via a 16 bit next field, so
-* we can have at most 2^16 of these. */
- if (unlikely(count > USHRT_MAX + 1)) {
- vq_err(vq, "Indirect buffer length too big: %d\n",
- indirect->len);
- return -E2BIG;
- }
-
- do {
- unsigned iov_count = *in_num + *out_num;
- if (unlikely(++found > count)) {
- vq_err(vq, "Loop detected: last one at %u "
- "indirect size %u\n",
- i, count);
- return -EINVAL;
- }
- if (unlikely(!copy_from_iter_full(, sizeof(desc), )))
{
- vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
-
[PATCH RFC v6 02/11] vhost: use batched get_vq_desc version
As testing shows no performance change, switch to that now.
Signed-off-by: Michael S. Tsirkin
Signed-off-by: Eugenio Pérez
Link: https://lore.kernel.org/r/20200401183118.8334-3-epere...@redhat.com
Signed-off-by: Michael S. Tsirkin
---
drivers/vhost/test.c | 2 +-
drivers/vhost/vhost.c | 318 --
drivers/vhost/vhost.h | 7 +-
3 files changed, 65 insertions(+), 262 deletions(-)
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index 0466921f4772..7d69778aaa26 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struct file
*f)
dev = >dev;
vqs[VHOST_TEST_VQ] = >vqs[VHOST_TEST_VQ];
n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick;
- vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV,
+ vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64,
VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, true, NULL);
f->private_data = n;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 180b7b58c76b..41d6b132c234 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -304,6 +304,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
{
vq->num = 1;
vq->ndescs = 0;
+ vq->first_desc = 0;
vq->desc = NULL;
vq->avail = NULL;
vq->used = NULL;
@@ -372,6 +373,11 @@ static int vhost_worker(void *data)
return 0;
}
+static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq)
+{
+ return vq->max_descs - UIO_MAXIOV;
+}
+
static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
{
kfree(vq->descs);
@@ -394,6 +400,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
for (i = 0; i < dev->nvqs; ++i) {
vq = dev->vqs[i];
vq->max_descs = dev->iov_limit;
+ if (vhost_vq_num_batch_descs(vq) < 0) {
+ return -EINVAL;
+ }
vq->descs = kmalloc_array(vq->max_descs,
sizeof(*vq->descs),
GFP_KERNEL);
@@ -1610,6 +1619,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int
ioctl, void __user *arg
vq->last_avail_idx = s.num;
/* Forget the cached index value. */
vq->avail_idx = vq->last_avail_idx;
+ vq->ndescs = vq->first_desc = 0;
break;
case VHOST_GET_VRING_BASE:
s.index = idx;
@@ -2078,253 +2088,6 @@ static unsigned next_desc(struct vhost_virtqueue *vq,
struct vring_desc *desc)
return next;
}
-static int get_indirect(struct vhost_virtqueue *vq,
- struct iovec iov[], unsigned int iov_size,
- unsigned int *out_num, unsigned int *in_num,
- struct vhost_log *log, unsigned int *log_num,
- struct vring_desc *indirect)
-{
- struct vring_desc desc;
- unsigned int i = 0, count, found = 0;
- u32 len = vhost32_to_cpu(vq, indirect->len);
- struct iov_iter from;
- int ret, access;
-
- /* Sanity check */
- if (unlikely(len % sizeof desc)) {
- vq_err(vq, "Invalid length in indirect descriptor: "
- "len 0x%llx not multiple of 0x%zx\n",
- (unsigned long long)len,
- sizeof desc);
- return -EINVAL;
- }
-
- ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len,
vq->indirect,
-UIO_MAXIOV, VHOST_ACCESS_RO);
- if (unlikely(ret < 0)) {
- if (ret != -EAGAIN)
- vq_err(vq, "Translation failure %d in indirect.\n",
ret);
- return ret;
- }
- iov_iter_init(, READ, vq->indirect, ret, len);
-
- /* We will use the result as an address to read from, so most
-* architectures only need a compiler barrier here. */
- read_barrier_depends();
-
- count = len / sizeof desc;
- /* Buffers are chained via a 16 bit next field, so
-* we can have at most 2^16 of these. */
- if (unlikely(count > USHRT_MAX + 1)) {
- vq_err(vq, "Indirect buffer length too big: %d\n",
- indirect->len);
- return -E2BIG;
- }
-
- do {
- unsigned iov_count = *in_num + *out_num;
- if (unlikely(++found > count)) {
- vq_err(vq, "Loop detected: last one at %u "
- "indirect size %u\n",
- i, count);
- return -EINVAL;
- }
- if (unlikely(!copy_from_iter_full(, sizeof(desc), )))
{
- vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
- i, (size_t)vhost64_to_cpu(vq,
