Add a new interface for userspace to preallocate memory that can be used with usbfs. This gives two primary benefits: - Zerocopy; data no longer needs to be copied between the userspace and the kernel, but can instead be read directly by the driver from userspace's buffers. This works for all kinds of transfers (even if nonsensical for control and interrupt transfers); isochronous also no longer need to memset() the buffer to zero to avoid leaking kernel data. - Once the buffers are allocated, USB transfers can no longer fail due to memory fragmentation; previously, long-running programs could run into problems finding a large enough contiguous memory chunk, especially on embedded systems or at high rates. Memory is allocated by using mmap() against the usbfs file descriptor, and similarly deallocated by munmap(). Once memory has been allocated, using it as pointers to a bulk or isochronous operation means you will automatically get zerocopy behavior. Note that this also means you cannot modify outgoing data until the transfer is complete. The same holds for data on the same cache lines as incoming data; DMA modifying them at the same time could lead to your changes being overwritten. There's a new capability USBDEVFS_CAP_MMAP that userspace can query to see if the running kernel supports this functionality, if just trying mmap() is not acceptable. Largely based on a patch by Markus Rechberger with some updates. The original patch can be found at: http://sundtek.de/support/devio_mmap_v0.4.diff Signed-off-by: Steinar H. Gunderson <sesse@xxxxxxxxxx> Signed-off-by: Markus Rechberger <mrechberger@xxxxxxxxx> Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> --- drivers/usb/core/devio.c | 230 +++++++++++++++++++++++++++++++++----- include/uapi/linux/usbdevice_fs.h | 1 + 2 files changed, 206 insertions(+), 25 deletions(-) diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c index 38ae877c..3349222 100644 --- a/drivers/usb/core/devio.c +++ b/drivers/usb/core/devio.c @@ -50,6 +50,7 @@ #include <linux/user_namespace.h> #include <linux/scatterlist.h> #include <linux/uaccess.h> +#include <linux/dma-mapping.h> #include <asm/byteorder.h> #include <linux/moduleparam.h> @@ -69,6 +70,7 @@ struct usb_dev_state { spinlock_t lock; /* protects the async urb lists */ struct list_head async_pending; struct list_head async_completed; + struct list_head memory_list; wait_queue_head_t wait; /* wake up if a request completed */ unsigned int discsignr; struct pid *disc_pid; @@ -79,6 +81,17 @@ struct usb_dev_state { u32 disabled_bulk_eps; }; +struct usb_memory { + struct list_head memlist; + int vma_use_count; + int urb_use_count; + u32 size; + void *mem; + dma_addr_t dma_handle; + unsigned long vm_start; + struct usb_dev_state *ps; +}; + struct async { struct list_head asynclist; struct usb_dev_state *ps; @@ -89,6 +102,7 @@ struct async { void __user *userbuffer; void __user *userurb; struct urb *urb; + struct usb_memory *usbm; unsigned int mem_usage; int status; u32 secid; @@ -157,6 +171,108 @@ static int connected(struct usb_dev_state *ps) ps->dev->state != USB_STATE_NOTATTACHED); } +static void dec_usb_memory_use_count(struct usb_memory *usbm, int *count) +{ + struct usb_dev_state *ps = usbm->ps; + unsigned long flags; + + spin_lock_irqsave(&ps->lock, flags); + --*count; + if (usbm->urb_use_count == 0 && usbm->vma_use_count == 0) { + list_del(&usbm->memlist); + spin_unlock_irqrestore(&ps->lock, flags); + + usb_free_coherent(ps->dev, usbm->size, usbm->mem, + usbm->dma_handle); + usbfs_decrease_memory_usage( + usbm->size + sizeof(struct usb_memory)); + kfree(usbm); + } else { + spin_unlock_irqrestore(&ps->lock, flags); + } +} + +static void usbdev_vm_open(struct vm_area_struct *vma) +{ + struct usb_memory *usbm = vma->vm_private_data; + unsigned long flags; + + spin_lock_irqsave(&usbm->ps->lock, flags); + ++usbm->vma_use_count; + spin_unlock_irqrestore(&usbm->ps->lock, flags); +} + +static void usbdev_vm_close(struct vm_area_struct *vma) +{ + struct usb_memory *usbm = vma->vm_private_data; + + dec_usb_memory_use_count(usbm, &usbm->vma_use_count); +} + +struct vm_operations_struct usbdev_vm_ops = { + .open = usbdev_vm_open, + .close = usbdev_vm_close +}; + +static int usbdev_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct usb_memory *usbm = NULL; + struct usb_dev_state *ps = file->private_data; + size_t size = vma->vm_end - vma->vm_start; + void *mem; + unsigned long flags; + dma_addr_t dma_handle; + int ret; + + ret = usbfs_increase_memory_usage(size + sizeof(struct usb_memory)); + if (ret) { + return ret; + } + + usbm = kzalloc(sizeof(struct usb_memory), GFP_KERNEL); + if (!usbm) { + usbfs_decrease_memory_usage( + size + sizeof(struct usb_memory)); + return -ENOMEM; + } + + mem = usb_alloc_coherent(ps->dev, size, GFP_KERNEL, &dma_handle); + if (!mem) { + usbfs_decrease_memory_usage( + size + sizeof(struct usb_memory)); + kfree(usbm); + return -ENOMEM; + } + + memset(mem, 0, size); + + usbm->mem = mem; + usbm->dma_handle = dma_handle; + usbm->size = size; + usbm->ps = ps; + usbm->vm_start = vma->vm_start; + usbm->vma_use_count = 1; + INIT_LIST_HEAD(&usbm->memlist); + + if (remap_pfn_range(vma, vma->vm_start, + virt_to_phys(usbm->mem) >> PAGE_SHIFT, + size, vma->vm_page_prot) < 0) { + dec_usb_memory_use_count(usbm, &usbm->vma_use_count); + return -EAGAIN; + } + + vma->vm_flags |= VM_IO; + vma->vm_flags |= (VM_DONTEXPAND | VM_DONTDUMP); + vma->vm_ops = &usbdev_vm_ops; + vma->vm_private_data = usbm; + + spin_lock_irqsave(&ps->lock, flags); + list_add_tail(&usbm->memlist, &ps->memory_list); + spin_unlock_irqrestore(&ps->lock, flags); + + return 0; +} + static loff_t usbdev_lseek(struct file *file, loff_t offset, int orig) { loff_t ret; @@ -297,8 +413,13 @@ static void free_async(struct async *as) if (sg_page(&as->urb->sg[i])) kfree(sg_virt(&as->urb->sg[i])); } + kfree(as->urb->sg); - kfree(as->urb->transfer_buffer); + if (as->usbm == NULL) + kfree(as->urb->transfer_buffer); + else + dec_usb_memory_use_count(as->usbm, &as->usbm->urb_use_count); + kfree(as->urb->setup_packet); usb_free_urb(as->urb); usbfs_decrease_memory_usage(as->mem_usage); @@ -910,6 +1031,7 @@ static int usbdev_open(struct inode *inode, struct file *file) INIT_LIST_HEAD(&ps->list); INIT_LIST_HEAD(&ps->async_pending); INIT_LIST_HEAD(&ps->async_completed); + INIT_LIST_HEAD(&ps->memory_list); init_waitqueue_head(&ps->wait); ps->discsignr = 0; ps->disc_pid = get_pid(task_pid(current)); @@ -962,6 +1084,13 @@ static int usbdev_release(struct inode *inode, struct file *file) free_async(as); as = async_getcompleted(ps); } + + /* Any elements still left on this list are still in use and cannot + * be deleted here, but will be freed once the counters go to 0 + * (see dec_usb_memory_use_count()). + */ + list_del(&ps->memory_list); + kfree(ps); return 0; } @@ -1283,6 +1412,31 @@ static int proc_setconfig(struct usb_dev_state *ps, void __user *arg) return status; } +static struct usb_memory * +find_memory_area(struct usb_dev_state *ps, const struct usbdevfs_urb *uurb) +{ + struct usb_memory *usbm = NULL, *iter; + unsigned long flags; + unsigned long uurb_start = (unsigned long)uurb->buffer; + + spin_lock_irqsave(&ps->lock, flags); + list_for_each_entry(iter, &ps->memory_list, memlist) { + if (uurb_start >= iter->vm_start && + uurb_start < iter->vm_start + iter->size) { + if (uurb->buffer_length > iter->vm_start + iter->size - + uurb_start) { + usbm = ERR_PTR(-EINVAL); + } else { + usbm = iter; + usbm->urb_use_count++; + } + break; + } + } + spin_unlock_irqrestore(&ps->lock, flags); + return usbm; +} + static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb, struct usbdevfs_iso_packet_desc __user *iso_frame_desc, void __user *arg) @@ -1439,6 +1593,19 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb goto error; } + as->usbm = find_memory_area(ps, uurb); + if (IS_ERR(as->usbm)) { + ret = PTR_ERR(as->usbm); + as->usbm = NULL; + goto error; + } + + /* do not use SG buffers when memory mapped segments + * are in use + */ + if (as->usbm) + num_sgs = 0; + u += sizeof(struct async) + sizeof(struct urb) + uurb->buffer_length + num_sgs * sizeof(struct scatterlist); ret = usbfs_increase_memory_usage(u); @@ -1476,29 +1643,35 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb totlen -= u; } } else if (uurb->buffer_length > 0) { - as->urb->transfer_buffer = kmalloc(uurb->buffer_length, - GFP_KERNEL); - if (!as->urb->transfer_buffer) { - ret = -ENOMEM; - goto error; - } + if (as->usbm) { + unsigned long uurb_start = (unsigned long)uurb->buffer; - if (!is_in) { - if (copy_from_user(as->urb->transfer_buffer, - uurb->buffer, - uurb->buffer_length)) { - ret = -EFAULT; + as->urb->transfer_buffer = as->usbm->mem + + (uurb_start - as->usbm->vm_start); + } else { + as->urb->transfer_buffer = kmalloc(uurb->buffer_length, + GFP_KERNEL); + if (!as->urb->transfer_buffer) { + ret = -ENOMEM; goto error; } - } else if (uurb->type == USBDEVFS_URB_TYPE_ISO) { - /* - * Isochronous input data may end up being - * discontiguous if some of the packets are short. - * Clear the buffer so that the gaps don't leak - * kernel data to userspace. - */ - memset(as->urb->transfer_buffer, 0, - uurb->buffer_length); + if (!is_in) { + if (copy_from_user(as->urb->transfer_buffer, + uurb->buffer, + uurb->buffer_length)) { + ret = -EFAULT; + goto error; + } + } else if (uurb->type == USBDEVFS_URB_TYPE_ISO) { + /* + * Isochronous input data may end up being + * discontiguous if some of the packets are + * short. Clear the buffer so that the gaps + * don't leak kernel data to userspace. + */ + memset(as->urb->transfer_buffer, 0, + uurb->buffer_length); + } } } as->urb->dev = ps->dev; @@ -1545,10 +1718,14 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb isopkt = NULL; as->ps = ps; as->userurb = arg; - if (is_in && uurb->buffer_length > 0) + if (as->usbm) { + unsigned long uurb_start = (unsigned long)uurb->buffer; + + as->urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP; + as->urb->transfer_dma = as->usbm->dma_handle + + (uurb_start - as->usbm->vm_start); + } else if (is_in && uurb->buffer_length > 0) as->userbuffer = uurb->buffer; - else - as->userbuffer = NULL; as->signr = uurb->signr; as->ifnum = ifnum; as->pid = get_pid(task_pid(current)); @@ -1604,6 +1781,8 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb return 0; error: + if (as && as->usbm) + dec_usb_memory_use_count(as->usbm, &as->usbm->urb_use_count); kfree(isopkt); kfree(dr); if (as) @@ -2047,7 +2226,7 @@ static int proc_get_capabilities(struct usb_dev_state *ps, void __user *arg) __u32 caps; caps = USBDEVFS_CAP_ZERO_PACKET | USBDEVFS_CAP_NO_PACKET_SIZE_LIM | - USBDEVFS_CAP_REAP_AFTER_DISCONNECT; + USBDEVFS_CAP_REAP_AFTER_DISCONNECT | USBDEVFS_CAP_MMAP; if (!ps->dev->bus->no_stop_on_short) caps |= USBDEVFS_CAP_BULK_CONTINUATION; if (ps->dev->bus->sg_tablesize) @@ -2373,6 +2552,7 @@ const struct file_operations usbdev_file_operations = { #ifdef CONFIG_COMPAT .compat_ioctl = usbdev_compat_ioctl, #endif + .mmap = usbdev_mmap, .open = usbdev_open, .release = usbdev_release, }; diff --git a/include/uapi/linux/usbdevice_fs.h b/include/uapi/linux/usbdevice_fs.h index 019ba1e..ecbd176 100644 --- a/include/uapi/linux/usbdevice_fs.h +++ b/include/uapi/linux/usbdevice_fs.h @@ -134,6 +134,7 @@ struct usbdevfs_hub_portinfo { #define USBDEVFS_CAP_NO_PACKET_SIZE_LIM 0x04 #define USBDEVFS_CAP_BULK_SCATTER_GATHER 0x08 #define USBDEVFS_CAP_REAP_AFTER_DISCONNECT 0x10 +#define USBDEVFS_CAP_MMAP 0x20 /* USBDEVFS_DISCONNECT_CLAIM flags & struct */ -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
