Re: [PATCH v2 4/8] vringh: support VA with iotlb
From: Stefano Garzarella <sgarzare@redhat.com>
Date: 2023-03-16 16:08:09
Also in:
kvm, lkml, virtualization
Subsystem:
the rest, virtio host (vhost) · Maintainers:
Linus Torvalds, "Michael S. Tsirkin", Jason Wang
On Fri, Mar 3, 2023 at 3:39 PM Eugenio Perez Martin [off-list ref] wrote:
On Thu, Mar 2, 2023 at 12:35 PM Stefano Garzarella [off-list ref] wrote:quoted
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; }