Re: [PATCH v2 4/8] vringh: support VA with iotlb

Stefano Garzarella
2023-03-16T16:08:22Z

On Fri, Mar 3, 2023 at 3:39 PM Eugenio Perez Martin <eperezma@redhat.com> wrote:
>
> On Thu, Mar 2, 2023 at 12:35 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
> >
> > vDPA supports the possibility to use user VA in the iotlb messages.
> > So, let's add support for user VA in vringh to use it in the vDPA
> > simulators.
> >
> > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> > ---
> >
> > Notes:
> > v2:
> > - replace kmap_atomic() with kmap_local_page() [see previous patch]
> > - fix cast warnings when build with W=1 C=1
> >
> > include/linux/vringh.h | 5 +-
> > drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
> > drivers/vdpa/vdpa_sim/vdpa_sim.c | 4 +-
> > drivers/vhost/vringh.c | 247 ++++++++++++++++++++++++------
> > 4 files changed, 205 insertions(+), 53 deletions(-)
> >

[...]

>
> It seems to me iotlb_translate_va and iotlb_translate_pa are very
> similar, their only difference is that the argument is that iov is
> iovec instead of bio_vec. And how to fill it, obviously.
>
> It would be great to merge both functions, only differing with a
> conditional on vrh->use_va, or generics, or similar. Or, if following
> the style of the rest of vringh code, to provide a callback to fill
> iovec (although I like conditional more).
>
> However I cannot think of an easy way to perform that without long
> macros or type erasure.

Thank you for pushing me :-)
I finally managed to avoid code duplication (partial patch attached,
but not yet fully tested).

@Jason: with this refactoring I removed copy_to_va/copy_to_pa, so I
also avoided getu16_iotlb_va/pa.

I will send the full patch in v3, but I would like to get your opinion
first ;-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 0ba3ef809e48..71dd67700e36 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -1096,8 +1096,7 @@ EXPORT_SYMBOL(vringh_need_notify_kern);

static int iotlb_translate(const struct vringh *vrh,
u64 addr, u64 len, u64 *translated,
- struct bio_vec iov[],
- int iov_size, u32 perm)
+ void *iov, int iov_size, bool iovec, u32 perm)
{
struct vhost_iotlb_map *map;
struct vhost_iotlb *iotlb = vrh->iotlb;
@@ -1107,7 +1106,7 @@ static int iotlb_translate(const struct vringh *vrh,
spin_lock(vrh->iotlb_lock);

while (len > s) {
- u64 size, pa, pfn;
+ u64 size;

if (unlikely(ret >= iov_size)) {
ret = -ENOBUFS;
@@ -1124,10 +1123,22 @@ static int iotlb_translate(const struct vringh *vrh,
}

size = map->size - addr + map->start;
- pa = map->addr + addr - map->start;
- pfn = pa >> PAGE_SHIFT;
- bvec_set_page(&iov[ret], pfn_to_page(pfn), min(len - s, size),
- pa & (PAGE_SIZE - 1));
+ if (iovec) {
+ struct iovec *iovec = iov;
+
+ iovec[ret].iov_len = min(len - s, size);
+ iovec[ret].iov_base = (void __user *)(unsigned long)
+ (map->addr + addr - map->start);
+ } else {
+ u64 pa = map->addr + addr - map->start;
+ u64 pfn = pa >> PAGE_SHIFT;
+ struct bio_vec *bvec = iov;
+
+ bvec_set_page(&bvec[ret], pfn_to_page(pfn),
+ min(len - s, size),
+ pa & (PAGE_SIZE - 1));
+ }
+
s += size;
addr += size;
++ret;
@@ -1141,26 +1152,38 @@ static int iotlb_translate(const struct vringh *vrh,
return ret;
}

+#define IOTLB_IOV_SIZE 16
+
static inline int copy_from_iotlb(const struct vringh *vrh, void *dst,
void *src, size_t len)
{
u64 total_translated = 0;

while (total_translated < len) {
- struct bio_vec iov[16];
+ union {
+ struct iovec iovec[IOTLB_IOV_SIZE];
+ struct bio_vec bvec[IOTLB_IOV_SIZE];
+ } iov;
struct iov_iter iter;
u64 translated;
int ret;

ret = iotlb_translate(vrh, (u64)(uintptr_t)src,
len - total_translated, &translated,
- iov, ARRAY_SIZE(iov), VHOST_MAP_RO);
+ &iov, IOTLB_IOV_SIZE, vrh->use_va,
+ VHOST_MAP_RO);
if (ret == -ENOBUFS)
- ret = ARRAY_SIZE(iov);
+ ret = IOTLB_IOV_SIZE;
else if (ret < 0)
return ret;

- iov_iter_bvec(&iter, ITER_SOURCE, iov, ret, translated);
+ if (vrh->use_va) {
+ iov_iter_init(&iter, ITER_SOURCE, iov.iovec, ret,
+ translated);
+ } else {
+ iov_iter_bvec(&iter, ITER_SOURCE, iov.bvec, ret,
+ translated);
+ }

ret = copy_from_iter(dst, translated, &iter);
if (ret < 0)
@@ -1180,20 +1203,30 @@ static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
u64 total_translated = 0;

while (total_translated < len) {
- struct bio_vec iov[16];
+ union {
+ struct iovec iovec[IOTLB_IOV_SIZE];
+ struct bio_vec bvec[IOTLB_IOV_SIZE];
+ } iov;
struct iov_iter iter;
u64 translated;
int ret;

ret = iotlb_translate(vrh, (u64)(uintptr_t)dst,
len - total_translated, &translated,
- iov, ARRAY_SIZE(iov), VHOST_MAP_WO);
+ &iov, IOTLB_IOV_SIZE, vrh->use_va,
+ VHOST_MAP_WO);
if (ret == -ENOBUFS)
- ret = ARRAY_SIZE(iov);
+ ret = IOTLB_IOV_SIZE;
else if (ret < 0)
return ret;

- iov_iter_bvec(&iter, ITER_DEST, iov, ret, translated);
+ if (vrh->use_va) {
+ iov_iter_init(&iter, ITER_DEST, iov.iovec, ret,
+ translated);
+ } else {
+ iov_iter_bvec(&iter, ITER_DEST, iov.bvec, ret,
+ translated);
+ }

ret = copy_to_iter(src, translated, &iter);
if (ret < 0)
@@ -1210,20 +1243,32 @@ static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
static inline int getu16_iotlb(const struct vringh *vrh,
u16 *val, const __virtio16 *p)
{
- struct bio_vec iov;
- void *kaddr, *from;
+ union {
+ struct iovec iovec;
+ struct bio_vec bvec;
+ } iov;
+ __virtio16 tmp;
int ret;

/* Atomic read is needed for getu16 */
- ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p), NULL,
- &iov, 1, VHOST_MAP_RO);
+ ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p),
+ NULL, &iov, 1, vrh->use_va, VHOST_MAP_RO);
if (ret < 0)
return ret;

- kaddr = kmap_local_page(iov.bv_page);
- from = kaddr + iov.bv_offset;
- *val = vringh16_to_cpu(vrh, READ_ONCE(*(__virtio16 *)from));
- kunmap_local(kaddr);
+ if (vrh->use_va) {
+ ret = __get_user(tmp, (__virtio16 __user *)iov.iovec.iov_base);
+ if (ret)
+ return ret;
+ } else {
+ void *kaddr = kmap_local_page(iov.bvec.bv_page);
+ void *from = kaddr + iov.bvec.bv_offset;
+
+ tmp = READ_ONCE(*(__virtio16 *)from);
+ kunmap_local(kaddr);
+ }
+
+ *val = vringh16_to_cpu(vrh, tmp);

return 0;
}
@@ -1231,20 +1276,32 @@ static inline int getu16_iotlb(const struct vringh *vrh,
static inline int putu16_iotlb(const struct vringh *vrh,
__virtio16 *p, u16 val)
{
- struct bio_vec iov;
- void *kaddr, *to;
+ union {
+ struct iovec iovec;
+ struct bio_vec bvec;
+ } iov;
+ __virtio16 tmp;
int ret;

/* Atomic write is needed for putu16 */
- ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p), NULL,
- &iov, 1, VHOST_MAP_WO);
+ ret = iotlb_translate(vrh, (u64)(uintptr_t)p, sizeof(*p),
+ NULL, &iov, 1, vrh->use_va, VHOST_MAP_RO);
if (ret < 0)
return ret;

- kaddr = kmap_local_page(iov.bv_page);
- to = kaddr + iov.bv_offset;
- WRITE_ONCE(*(__virtio16 *)to, cpu_to_vringh16(vrh, val));
- kunmap_local(kaddr);
+ tmp = cpu_to_vringh16(vrh, val);
+
+ if (vrh->use_va) {
+ ret = __put_user(tmp, (__virtio16 __user *)iov.iovec.iov_base);
+ if (ret)
+ return ret;
+ } else {
+ void *kaddr = kmap_local_page(iov.bvec.bv_page);
+ void *to = kaddr + iov.bvec.bv_offset;
+
+ WRITE_ONCE(*(__virtio16 *)to, tmp);
+ kunmap_local(kaddr);
+ }

return 0;
}