On Wed, 6 Jan 2016, Lingzhu Xiang wrote: > On Wed, Nov 25, 2015 at 7:19 PM, Steinar H. Gunderson <sesse@xxxxxxxxxx> wrote: > > Add a new interface for userspace to preallocate memory that can be > > used with usbfs. This gives two primary benefits: > > I got this when trying to allocate a little bit large buffer (~4MB) > using the new userspace libusb_dev_mem_alloc(): > > > [ 1706.212407] usb 2-1.1: reset SuperSpeed USB device number 3 using xhci_hcd > > [ 1706.234823] xhci_hcd 0000:00:14.0: swiotlb buffer is full (sz: 4325376 bytes) > > [ 1706.234827] swiotlb: coherent allocation failed for device 0000:00:14.0 size=4325376 > > [ 1706.234830] CPU: 1 PID: 3233 Comm: Protonect Tainted: G U W 4.4.0-rc8-amd64 #1 Debian 4.4~rc8-1~exp1 > > [ 1706.234831] Hardware name: LENOVO 20ALCTO1WW/20ALCTO1WW, BIOS GIET76WW (2.26 ) 08/27/2014 > > [ 1706.234833] 0000000000000000 000000000f50c266 ffffffff812e6019 ffffffffffffffff > > [ 1706.234836] ffffffff8130dc45 ffff88020000000b 0000000000420000 ffffffff81a2a0e0 > > [ 1706.234838] ffff880206263d80 0000000000000000 ffff88021c892f40 0000000000420040 > > [ 1706.234841] Call Trace: > > [ 1706.234847] [<ffffffff812e6019>] ? dump_stack+0x40/0x57 > > [ 1706.234851] [<ffffffff8130dc45>] ? swiotlb_alloc_coherent+0x135/0x150 > > [ 1706.234867] [<ffffffffa021deb1>] ? hcd_buffer_alloc+0xb1/0x130 [usbcore] > > [ 1706.234875] [<ffffffffa0221ab5>] ? usbdev_mmap+0xa5/0x1b0 [usbcore] > > [ 1706.234880] [<ffffffff813bbc25>] ? tty_insert_flip_string_fixed_flag+0x85/0xe0 > > [ 1706.234885] [<ffffffff8119af87>] ? mmap_region+0x3e7/0x660 > > [ 1706.234888] [<ffffffff8119b536>] ? do_mmap+0x336/0x420 > > [ 1706.234892] [<ffffffff8118213f>] ? vm_mmap_pgoff+0xaf/0xf0 > > [ 1706.234895] [<ffffffff811999dd>] ? SyS_mmap_pgoff+0x1ad/0x270 > > [ 1706.234898] [<ffffffff811d53b6>] ? SyS_write+0x76/0xc0 > > [ 1706.234903] [<ffffffff815829f2>] ? system_call_fast_compare_end+0xc/0x67 > > I understand there are some requirements on the allocation such that > large blocks are not always available. But what is the proper way to > determine the upper limit of the size such that the user can avoid > generating warnings like this? (Also, the application really wants to > be able to allocate large buffers, maybe tune swiotlb=?.) It's debatable whether this should have generated a warning. Why doesn't dma_alloc_coherent() simply fail silently? Alan Stern -- 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
