On Sun, Dec 06, 2015 at 01:06:08AM +0100, Steinar H. Gunderson wrote: > I'll try to update your patch with the other suggestions tomorrow. Thanks! Here we are. Lightly tested, I believe all comments should be addressed. /* Steinar */ >From 73833276a4f359c35edffc2a741dba57f2e82a12 Mon Sep 17 00:00:00 2001 From: "Steinar H. Gunderson" <sesse@xxxxxxxxxx> Date: Thu, 26 Nov 2015 01:19:13 +0100 Subject: [PATCH] Add support for usbfs zerocopy. 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 both bulk and isochronous 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. 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> --- drivers/usb/core/devio.c | 202 ++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 192 insertions(+), 10 deletions(-) diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c index 38ae877c..40f988e 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 +171,107 @@ 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; + + 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 +412,13 @@ 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 +1030,7 @@ 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 +1083,13 @@ 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 +1411,31 @@ 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 +1592,19 @@ 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); + 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); @@ -1476,14 +1642,23 @@ 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; + + 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; + } } - if (!is_in) { + if (as->usbm) { + ; /* Transfer buffer is okay as it is */ + } else if (!is_in) { if (copy_from_user(as->urb->transfer_buffer, uurb->buffer, uurb->buffer_length)) { @@ -1545,10 +1720,14 @@ 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 +1783,8 @@ 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) @@ -2373,6 +2554,7 @@ 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, }; -- 2.1.4 -- Homepage: https://www.sesse.net/ -- 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
