Re: [PATCH v6] usbip: Implement SG support to vhci-hcd and stub driver

From: Suwan Kim
Date: Mon Aug 26 2019 - 09:53:44 EST

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In reply to: shuah: "Re: [PATCH v6] usbip: Implement SG support to vhci-hcd and stub driver"
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On Sat, Aug 24, 2019 at 01:41:50PM -0600, shuah wrote:
> Hi Suwan,
>
> Thanks for the patch. A few comments.
>
> On 8/22/19 4:11 PM, Suwan Kim wrote:
> > There are bugs on vhci with usb 3.0 storage device. In USB, each SG
> > list entry buffer should be divisible by the bulk max packet size.
> > But with native SG support, this problem doesn't matter because the
> > SG buffer is treated as contiguous buffer. But without native SG
> > support, USB storage driver breaks SG list into several URBs and the
> > error occurs because of a buffer size of URB that cannot be divided
> > by the bulk max packet size. The error situation is as follows.
> >
> > When USB Storage driver requests 31.5 KB data and has SG list which
> > has 3584 bytes buffer followed by 7 4096 bytes buffer for some
> > reason. USB Storage driver splits this SG list into several URBs
> > because VHCI doesn't support SG and sends them separately. So the
> > first URB buffer size is 3584 bytes. When receiving data from device,
> > USB 3.0 device sends data packet of 1024 bytes size because the max
> > packet size of BULK pipe is 1024 bytes. So device sends 4096 bytes.
> > But the first URB buffer has only 3584 bytes buffer size. So host
> > controller terminates the transfer even though there is more data to
> > receive. So, vhci needs to support SG transfer to prevent this error.
> >
> > In this patch, vhci supports SG regardless of whether the server's
> > host controller supports SG or not, because stub driver splits SG
> > list into several URBs if the server's host controller doesn't
> > support SG.
> >
> > To support SG, vhci sets URB_DMA_MAP_SG flag in urb->transfer_flags
> > if URB has SG list and this flag will tell stub driver to use SG
> > list. After receiving urb from stub driver, vhci clear URB_DMA_MAP_SG
> > flag to avoid unnecessary dma unmapping in HCD.
> >
> > vhci sends each SG list entry to stub driver. Then, stub driver sees
> > the total length of the buffer and allocates SG table and pages
> > according to the total buffer length calling sgl_alloc(). After stub
> > driver receives completed URB, it again sends each SG list entry to
> > vhci.
> >
> > If the server's host controller doesn't support SG, stub driver
> > breaks a single SG request into several URBs and submits them to
> > the server's host controller. When all the split URBs are completed,
> > stub driver reassembles the URBs into a single return command and
> > sends it to vhci.
> >
> > Moreover, in the situation where vhci supports SG, but stub driver
> > does not, or vice versa, usbip works normally. Because there is no
> > protocol modification, there is no problem in communication between
> > server and client even if the one has a kernel without SG support.
> >
> > In the case of vhci supports SG and stub driver doesn't, because
> > vhci sends only the total length of the buffer to stub driver as
> > it did before the patch applied, stub driver only needs to allocate
> > the required length of buffers using only kmalloc() regardless of
> > whether vhci supports SG or not. But stub driver has to allocate
> > buffer with kmalloc() as much as the total length of SG buffer which
> > is quite huge when vhci sends SG request, so it has overhead in
> > buffer allocation in this situation.
> >
> > If stub driver needs to send data buffer to vhci because of IN pipe,
> > stub driver also sends only total length of buffer as metadata and
> > then sends real data as vhci does. Then vhci receive data from stub
> > driver and store it to the corresponding buffer of SG list entry.
> >
> > And for the case of stub driver supports SG and vhci doesn't, since
> > the USB storage driver checks that vhci doesn't support SG and sends
> > the request to stub driver by splitting the SG list into multiple
> > URBs, stub driver allocates a buffer for each URB with kmalloc() as
> > it did before this patch.
> >
> > * Test environment
> >
> > Test uses two difference machines and two different kernel version
> > to make mismatch situation between the client and the server where
> > vhci supports SG, but stub driver does not, or vice versa. All tests
> > are conducted in both full SG support that both vhci and stub support
> > SG and half SG support that is the mismatch situation.
> >
> > - Test kernel version
> > - 5.2-rc6 with SG support
> > - 5.1.20-200.fc29.x86_64 without SG support
> >
>
> Please test this patch with 5.3-rc6 and with Christoph's DMA changes.

I have tested 5.3-rc6 with Christoph's patch series and greg's
usb-next branch (5.3-rc5). It works normally. I will modify commit
log and resend the patch.

> > * SG support test
> >
> > - Test devices
> > - Super-speed storage device - SanDisk Ultra USB 3.0
> > - High-speed storage device - SMI corporation USB 2.0 flash drive
> >
> > - Test description
> >
> > Test read and write operation of mass storage device that uses the
> > BULK transfer. In test, the client reads and writes files whose size
> > is over 1G and it works normally.
> >
> > * Regression test
> >
> > - Test devices
> > - Super-speed device - Logitech Brio webcam
> > - High-speed device - Logitech C920 HD Pro webcam
> > - Full-speed device - Logitech bluetooth mouse
> > - Britz BR-Orion speaker
> > - Low-speed device - Logitech wired mouse
> >
> > - Test description
> >
> > Moving and click test for mouse. To test the webcam, use gnome-cheese.
> > To test the speaker, play music and video on the client. All works
> > normally.
> >
> > * VUDC compatibility test
> >
> > VUDC also works well with this patch. Tests are done with two USB
> > gadget created by CONFIGFS USB gadget. Both use the BULK pipe.
> >
> > 1. Serial gadget
> > 2. Mass storage gadget
> >
> > - Serial gadget test
> >
> > Serial gadget on the host sends and receives data using cat command
> > on the /dev/ttyGS<N>. The client uses minicom to communicate with
> > the serial gadget.
> >
> > - Mass storage gadget test
> >
> > After connecting the gadget with vhci, use "dd" to test read and
> > write operation on the client side.
> >
> > Read - dd if=/dev/sd<N> iflag=direct of=/dev/null bs=1G count=1
> > Write - dd if=<my file path> iflag=direct of=/dev/sd<N> bs=1G count=1
> >
> > Signed-off-by: Suwan Kim <suwan.kim027@xxxxxxxxx>
> > ---
> > v5 - v6
> > - The patch1 is dropped because Christoph's patch series does what
> > patch1 did. And patch1 is no longer needed as vhci doesn't set
> > HCD_DMA flag.
> >
> > - Because the patch1 is dropped, move setting URB_DMA_MAP_SG flag
> > from vhci_map_urb_for_dma() which is removed in v6 to
> > vhci_send_cmd_submit().
>
> Assuming you meant "moved" Wasn't clear what you meant by "removed
> in v6 to vhci_send_cmd_submit()."

What I meant was that because vhci_map_urb_for_dma() was removed
in v6, I moved setting flag to vhci_send_cmd_submit().

> >
> > - Add clearing URB_DMA_MAP_SG flag before vhci gives back URB to
> > itâs driver to avoid dma unmapping in hcd_unmap_urb_for_dma().
> >
>
> Please see comment - I think the flag set should be moved down
> after kalloc.
>
> > - Rewrite the desxcription about setting URB_DMA_MAP_SG flag in
> > commit log.
> >
> > v4 - v5
> > - Add the test description about SG support test and regression test
> > for other USB devices which have various speed.
> > - Fix list_del() error in stub_device_cleanup_urbs()
> > - when stub_device_cleanup_urbs() calls stub_pirv_pop() to get a
> > stub_priv, stub_priv_pop() uses list_del_init() instead of
> > list_del(). After getting the stub_priv, stub_device_cleanup_urbs()
> > calls stub_free_priv_and_urb() and it checks if list of the
> > stub_priv is empty. Because stub_priv_pop() calls list_del_init(),
> > stub_free_priv_and_urb() doesn't call list_del()
> >
> > v3 - v4
> > - Rewrite the description about the vhci bug with USB 3.0 storage
> > device.
> > - Add the description about the test with VUDC.
> > - Fix the error message in stub_recv_cmd_unlink().
> >
> > v2 - v3
> > - Rewrite the commit log to make it more clear.
> > - Add the description about the mismatch situation in commit log.
> > - Run chechpatch.pl and fix errors with coding style and typos.
> > - Fix the error path of usbip_recv_xbuff() to stop receiving data
> > after TCP error occurs.
> > - Consolidate the duplicated error path in usbip_recv_xbuff() and
> > vhci_send_cmd_submit().
> > - Undo the unnecessary changes
> > * Undo the deletion of empty line in stub_send_ret_submit()
> > * Move memset() lines in stub_send_ret_submit() to the original
> > position.
> >
> > v1 - v2
> > - Add the logic that splits single SG request into several URBs in
> > stub driver if serverâs HC doesnât support SG.
> > ---
> > drivers/usb/usbip/stub.h | 7 +-
> > drivers/usb/usbip/stub_main.c | 57 ++++++---
> > drivers/usb/usbip/stub_rx.c | 204 ++++++++++++++++++++++---------
> > drivers/usb/usbip/stub_tx.c | 99 +++++++++++----
> > drivers/usb/usbip/usbip_common.c | 59 ++++++---
> > drivers/usb/usbip/vhci_hcd.c | 12 +-
> > drivers/usb/usbip/vhci_rx.c | 3 +
> > drivers/usb/usbip/vhci_tx.c | 66 ++++++++--
> > 8 files changed, 380 insertions(+), 127 deletions(-)
> >
> > diff --git a/drivers/usb/usbip/stub.h b/drivers/usb/usbip/stub.h
> > index 35618ceb2791..d11270560c24 100644
> > --- a/drivers/usb/usbip/stub.h
> > +++ b/drivers/usb/usbip/stub.h
> > @@ -52,7 +52,11 @@ struct stub_priv {
> > unsigned long seqnum;
> > struct list_head list;
> > struct stub_device *sdev;
> > - struct urb *urb;
> > + struct urb **urbs;
> > + struct scatterlist *sgl;
> > + int num_urbs;
> > + int completed_urbs;
> > + int urb_status;
> > int unlinking;
> > };
> > @@ -86,6 +90,7 @@ extern struct usb_device_driver stub_driver;
> > struct bus_id_priv *get_busid_priv(const char *busid);
> > void put_busid_priv(struct bus_id_priv *bid);
> > int del_match_busid(char *busid);
> > +void stub_free_priv_and_urb(struct stub_priv *priv);
> > void stub_device_cleanup_urbs(struct stub_device *sdev);
> > /* stub_rx.c */
> > diff --git a/drivers/usb/usbip/stub_main.c b/drivers/usb/usbip/stub_main.c
> > index 2e4bfccd4bfc..c1c0bbc9f8b1 100644
> > --- a/drivers/usb/usbip/stub_main.c
> > +++ b/drivers/usb/usbip/stub_main.c
> > @@ -6,6 +6,7 @@
> > #include <linux/string.h>
> > #include <linux/module.h>
> > #include <linux/device.h>
> > +#include <linux/scatterlist.h>
> > #include "usbip_common.h"
> > #include "stub.h"
> > @@ -281,13 +282,49 @@ static struct stub_priv *stub_priv_pop_from_listhead(struct list_head *listhead)
> > struct stub_priv *priv, *tmp;
> > list_for_each_entry_safe(priv, tmp, listhead, list) {
> > - list_del(&priv->list);
> > + list_del_init(&priv->list);
> > return priv;
> > }
> > return NULL;
> > }
> > +void stub_free_priv_and_urb(struct stub_priv *priv)
> > +{
> > + struct urb *urb;
> > + int i;
> > +
> > + for (i = 0; i < priv->num_urbs; i++) {
> > + urb = priv->urbs[i];
> > +
> > + if (!urb)
> > + return;
> > +
> > + kfree(urb->setup_packet);
> > + urb->setup_packet = NULL;
> > +
> > +
> > + if (urb->transfer_buffer && !priv->sgl) {
> > + kfree(urb->transfer_buffer);
> > + urb->transfer_buffer = NULL;
> > + }
> > +
> > + if (urb->num_sgs) {
> > + sgl_free(urb->sg);
> > + urb->sg = NULL;
> > + urb->num_sgs = 0;
> > + }
> > +
> > + usb_free_urb(urb);
> > + }
> > + if (!list_empty(&priv->list))
> > + list_del(&priv->list);
> > + if (priv->sgl)
> > + sgl_free(priv->sgl);
> > + kfree(priv->urbs);
> > + kmem_cache_free(stub_priv_cache, priv);
> > +}
> > +
> > static struct stub_priv *stub_priv_pop(struct stub_device *sdev)
> > {
> > unsigned long flags;
> > @@ -314,25 +351,15 @@ static struct stub_priv *stub_priv_pop(struct stub_device *sdev)
> > void stub_device_cleanup_urbs(struct stub_device *sdev)
> > {
> > struct stub_priv *priv;
> > - struct urb *urb;
> > + int i;
> > dev_dbg(&sdev->udev->dev, "Stub device cleaning up urbs\n");
> > while ((priv = stub_priv_pop(sdev))) {
> > - urb = priv->urb;
> > - dev_dbg(&sdev->udev->dev, "free urb seqnum %lu\n",
> > - priv->seqnum);
> > - usb_kill_urb(urb);
> > -
> > - kmem_cache_free(stub_priv_cache, priv);
> > + for (i = 0; i < priv->num_urbs; i++)
> > + usb_kill_urb(priv->urbs[i]);
> > - kfree(urb->transfer_buffer);
> > - urb->transfer_buffer = NULL;
> > -
> > - kfree(urb->setup_packet);
> > - urb->setup_packet = NULL;
> > -
> > - usb_free_urb(urb);
> > + stub_free_priv_and_urb(priv);
> > }
> > }
> > diff --git a/drivers/usb/usbip/stub_rx.c b/drivers/usb/usbip/stub_rx.c
> > index b0a855acafa3..66edfeea68fe 100644
> > --- a/drivers/usb/usbip/stub_rx.c
> > +++ b/drivers/usb/usbip/stub_rx.c
> > @@ -7,6 +7,7 @@
> > #include <linux/kthread.h>
> > #include <linux/usb.h>
> > #include <linux/usb/hcd.h>
> > +#include <linux/scatterlist.h>
> > #include "usbip_common.h"
> > #include "stub.h"
> > @@ -201,7 +202,7 @@ static void tweak_special_requests(struct urb *urb)
> > static int stub_recv_cmd_unlink(struct stub_device *sdev,
> > struct usbip_header *pdu)
> > {
> > - int ret;
> > + int ret, i;
> > unsigned long flags;
> > struct stub_priv *priv;
> > @@ -246,12 +247,14 @@ static int stub_recv_cmd_unlink(struct stub_device *sdev,
> > * so a driver in a client host will know the failure
> > * of the unlink request ?
> > */
> > - ret = usb_unlink_urb(priv->urb);
> > - if (ret != -EINPROGRESS)
> > - dev_err(&priv->urb->dev->dev,
> > - "failed to unlink a urb # %lu, ret %d\n",
> > - priv->seqnum, ret);
> > -
> > + for (i = priv->completed_urbs; i < priv->num_urbs; i++) {
> > + ret = usb_unlink_urb(priv->urbs[i]);
> > + if (ret != -EINPROGRESS)
> > + dev_err(&priv->urbs[i]->dev->dev,
> > + "failed to unlink %d/%d urb of seqnum %lu, ret %d\n",
> > + i + 1, priv->num_urbs,
> > + priv->seqnum, ret);
> > + }
> > return 0;
> > }
> > @@ -433,14 +436,36 @@ static void masking_bogus_flags(struct urb *urb)
> > urb->transfer_flags &= allowed;
> > }
> > +static int stub_recv_xbuff(struct usbip_device *ud, struct stub_priv *priv)
> > +{
> > + int ret;
> > + int i;
> > +
> > + for (i = 0; i < priv->num_urbs; i++) {
> > + ret = usbip_recv_xbuff(ud, priv->urbs[i]);
> > + if (ret < 0)
> > + break;
> > + }
> > +
> > + return ret;
> > +}
> > +
> > static void stub_recv_cmd_submit(struct stub_device *sdev,
> > struct usbip_header *pdu)
> > {
> > - int ret;
> > struct stub_priv *priv;
> > struct usbip_device *ud = &sdev->ud;
> > struct usb_device *udev = sdev->udev;
> > + struct scatterlist *sgl = NULL, *sg;
> > + void *buffer = NULL;
> > + unsigned long long buf_len;
> > + int nents;
> > + int num_urbs = 1;
> > int pipe = get_pipe(sdev, pdu);
> > + int use_sg = pdu->u.cmd_submit.transfer_flags & URB_DMA_MAP_SG;
> > + int support_sg = 1;
> > + int np = 0;
> > + int ret, i;
> > if (pipe == -1)
> > return;
> > @@ -449,76 +474,139 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
> > if (!priv)
> > return;
> > - /* setup a urb */
> > - if (usb_pipeisoc(pipe))
> > - priv->urb = usb_alloc_urb(pdu->u.cmd_submit.number_of_packets,
> > - GFP_KERNEL);
> > - else
> > - priv->urb = usb_alloc_urb(0, GFP_KERNEL);
> > + buf_len = (unsigned long long)pdu->u.cmd_submit.transfer_buffer_length;
> > - if (!priv->urb) {
> > - usbip_event_add(ud, SDEV_EVENT_ERROR_MALLOC);
> > - return;
> > + /* allocate urb transfer buffer, if needed */
> > + if (buf_len) {
> > + if (use_sg) {
> > + sgl = sgl_alloc(buf_len, GFP_KERNEL, &nents);
> > + if (!sgl)
> > + goto err_malloc;
> > + } else {
> > + buffer = kzalloc(buf_len, GFP_KERNEL);
> > + if (!buffer)
> > + goto err_malloc;
> > + }
> > }
> > - /* allocate urb transfer buffer, if needed */
> > - if (pdu->u.cmd_submit.transfer_buffer_length > 0) {
> > - priv->urb->transfer_buffer =
> > - kzalloc(pdu->u.cmd_submit.transfer_buffer_length,
> > - GFP_KERNEL);
> > - if (!priv->urb->transfer_buffer) {
> > + /* Check if the server's HCD supports SG */
> > + if (use_sg && !udev->bus->sg_tablesize) {
> > + /*
> > + * If the server's HCD doesn't support SG, break a single SG
> > + * request into several URBs and map each SG list entry to
> > + * corresponding URB buffer. The previously allocated SG
> > + * list is stored in priv->sgl (If the server's HCD support SG,
> > + * SG list is stored only in urb->sg) and it is used as an
> > + * indicator that the server split single SG request into
> > + * several URBs. Later, priv->sgl is used by stub_complete() and
> > + * stub_send_ret_submit() to reassemble the divied URBs.
> > + */
> > + support_sg = 0;
> > + num_urbs = nents;
> > + priv->completed_urbs = 0;
> > + pdu->u.cmd_submit.transfer_flags &= ~URB_DMA_MAP_SG;
> > + }
> > +
> > + /* allocate urb array */
> > + priv->num_urbs = num_urbs;
> > + priv->urbs = kmalloc_array(num_urbs, sizeof(*priv->urbs), GFP_KERNEL);
> > + if (!priv->urbs)
> > + goto err_urbs;
> > +
> > + /* setup a urb */
> > + if (support_sg) {
> > + if (usb_pipeisoc(pipe))
> > + np = pdu->u.cmd_submit.number_of_packets;
> > +
> > + priv->urbs[0] = usb_alloc_urb(np, GFP_KERNEL);
> > + if (!priv->urbs[0])
> > + goto err_urb;
> > +
> > + if (buf_len) {
> > + if (use_sg) {
> > + priv->urbs[0]->sg = sgl;
> > + priv->urbs[0]->num_sgs = nents;
> > + priv->urbs[0]->transfer_buffer = NULL;
> > + } else {
> > + priv->urbs[0]->transfer_buffer = buffer;
> > + }
> > + }
> > +
> > + /* copy urb setup packet */
> > + priv->urbs[0]->setup_packet = kmemdup(&pdu->u.cmd_submit.setup,
> > + 8, GFP_KERNEL);
> > + if (!priv->urbs[0]->setup_packet) {
> > usbip_event_add(ud, SDEV_EVENT_ERROR_MALLOC);
> > return;
> > }
> > - }
> > - /* copy urb setup packet */
> > - priv->urb->setup_packet = kmemdup(&pdu->u.cmd_submit.setup, 8,
> > - GFP_KERNEL);
> > - if (!priv->urb->setup_packet) {
> > - dev_err(&udev->dev, "allocate setup_packet\n");
> > - usbip_event_add(ud, SDEV_EVENT_ERROR_MALLOC);
> > - return;
> > + usbip_pack_pdu(pdu, priv->urbs[0], USBIP_CMD_SUBMIT, 0);
> > + } else {
> > + for_each_sg(sgl, sg, nents, i) {
> > + priv->urbs[i] = usb_alloc_urb(0, GFP_KERNEL);
> > + /* The URBs which is previously allocated will be freed
> > + * in stub_device_cleanup_urbs() if error occurs.
> > + */
> > + if (!priv->urbs[i])
> > + goto err_urb;
> > +
> > + usbip_pack_pdu(pdu, priv->urbs[i], USBIP_CMD_SUBMIT, 0);
> > + priv->urbs[i]->transfer_buffer = sg_virt(sg);
> > + priv->urbs[i]->transfer_buffer_length = sg->length;
> > + }
> > + priv->sgl = sgl;
> > }
> > - /* set other members from the base header of pdu */
> > - priv->urb->context = (void *) priv;
> > - priv->urb->dev = udev;
> > - priv->urb->pipe = pipe;
> > - priv->urb->complete = stub_complete;
> > + for (i = 0; i < num_urbs; i++) {
> > + /* set other members from the base header of pdu */
> > + priv->urbs[i]->context = (void *) priv;
> > + priv->urbs[i]->dev = udev;
> > + priv->urbs[i]->pipe = pipe;
> > + priv->urbs[i]->complete = stub_complete;
> > - usbip_pack_pdu(pdu, priv->urb, USBIP_CMD_SUBMIT, 0);
> > + /* no need to submit an intercepted request, but harmless? */
> > + tweak_special_requests(priv->urbs[i]);
> > + masking_bogus_flags(priv->urbs[i]);
> > + }
> > - if (usbip_recv_xbuff(ud, priv->urb) < 0)
> > + if (stub_recv_xbuff(ud, priv) < 0)
> > return;
> > - if (usbip_recv_iso(ud, priv->urb) < 0)
> > + if (usbip_recv_iso(ud, priv->urbs[0]) < 0)
> > return;
> > - /* no need to submit an intercepted request, but harmless? */
> > - tweak_special_requests(priv->urb);
> > -
> > - masking_bogus_flags(priv->urb);
> > /* urb is now ready to submit */
> > - ret = usb_submit_urb(priv->urb, GFP_KERNEL);
> > -
> > - if (ret == 0)
> > - usbip_dbg_stub_rx("submit urb ok, seqnum %u\n",
> > - pdu->base.seqnum);
> > - else {
> > - dev_err(&udev->dev, "submit_urb error, %d\n", ret);
> > - usbip_dump_header(pdu);
> > - usbip_dump_urb(priv->urb);
> > -
> > - /*
> > - * Pessimistic.
> > - * This connection will be discarded.
> > - */
> > - usbip_event_add(ud, SDEV_EVENT_ERROR_SUBMIT);
> > + for (i = 0; i < priv->num_urbs; i++) {
> > + ret = usb_submit_urb(priv->urbs[i], GFP_KERNEL);
> > +
> > + if (ret == 0)
> > + usbip_dbg_stub_rx("submit urb ok, seqnum %u\n",
> > + pdu->base.seqnum);
> > + else {
> > + dev_err(&udev->dev, "submit_urb error, %d\n", ret);
> > + usbip_dump_header(pdu);
> > + usbip_dump_urb(priv->urbs[i]);
> > +
> > + /*
> > + * Pessimistic.
> > + * This connection will be discarded.
> > + */
> > + usbip_event_add(ud, SDEV_EVENT_ERROR_SUBMIT);
> > + break;
> > + }
> > }
> > usbip_dbg_stub_rx("Leave\n");
> > + return;
> > +
> > +err_urb:
> > + kfree(priv->urbs);
> > +err_urbs:
> > + kfree(buffer);
> > + sgl_free(sgl);
> > +err_malloc:
> > + usbip_event_add(ud, SDEV_EVENT_ERROR_MALLOC);
> > }
> > /* recv a pdu */
> > diff --git a/drivers/usb/usbip/stub_tx.c b/drivers/usb/usbip/stub_tx.c
> > index f0ec41a50cbc..36010a82b359 100644
> > --- a/drivers/usb/usbip/stub_tx.c
> > +++ b/drivers/usb/usbip/stub_tx.c
> > @@ -5,25 +5,11 @@
> > #include <linux/kthread.h>
> > #include <linux/socket.h>
> > +#include <linux/scatterlist.h>
> > #include "usbip_common.h"
> > #include "stub.h"
> > -static void stub_free_priv_and_urb(struct stub_priv *priv)
> > -{
> > - struct urb *urb = priv->urb;
> > -
> > - kfree(urb->setup_packet);
> > - urb->setup_packet = NULL;
> > -
> > - kfree(urb->transfer_buffer);
> > - urb->transfer_buffer = NULL;
> > -
> > - list_del(&priv->list);
> > - kmem_cache_free(stub_priv_cache, priv);
> > - usb_free_urb(urb);
> > -}
> > -
> > /* be in spin_lock_irqsave(&sdev->priv_lock, flags) */
> > void stub_enqueue_ret_unlink(struct stub_device *sdev, __u32 seqnum,
> > __u32 status)
> > @@ -85,6 +71,22 @@ void stub_complete(struct urb *urb)
> > break;
> > }
> > + /*
> > + * If the server breaks single SG request into the several URBs, the
> > + * URBs must be reassembled before sending completed URB to the vhci.
> > + * Don't wake up the tx thread until all the URBs are completed.
> > + */
> > + if (priv->sgl) {
> > + priv->completed_urbs++;
> > +
> > + /* Only save the first error status */
> > + if (urb->status && !priv->urb_status)
> > + priv->urb_status = urb->status;
> > +
> > + if (priv->completed_urbs < priv->num_urbs)
> > + return;
> > + }
> > +
> > /* link a urb to the queue of tx. */
> > spin_lock_irqsave(&sdev->priv_lock, flags);
> > if (sdev->ud.tcp_socket == NULL) {
> > @@ -156,18 +158,22 @@ static int stub_send_ret_submit(struct stub_device *sdev)
> > size_t total_size = 0;
> > while ((priv = dequeue_from_priv_tx(sdev)) != NULL) {
> > - int ret;
> > - struct urb *urb = priv->urb;
> > + struct urb *urb = priv->urbs[0];
> > struct usbip_header pdu_header;
> > struct usbip_iso_packet_descriptor *iso_buffer = NULL;
> > struct kvec *iov = NULL;
> > + struct scatterlist *sg;
> > + u32 actual_length = 0;
> > int iovnum = 0;
> > + int ret;
> > + int i;
> > txsize = 0;
> > memset(&pdu_header, 0, sizeof(pdu_header));
> > memset(&msg, 0, sizeof(msg));
> > - if (urb->actual_length > 0 && !urb->transfer_buffer) {
> > + if (urb->actual_length > 0 && !urb->transfer_buffer &&
> > + !urb->num_sgs) {
> > dev_err(&sdev->udev->dev,
> > "urb: actual_length %d transfer_buffer null\n",
> > urb->actual_length);
> > @@ -176,6 +182,11 @@ static int stub_send_ret_submit(struct stub_device *sdev)
> > if (usb_pipetype(urb->pipe) == PIPE_ISOCHRONOUS)
> > iovnum = 2 + urb->number_of_packets;
> > + else if (usb_pipein(urb->pipe) && urb->actual_length > 0 &&
> > + urb->num_sgs)
> > + iovnum = 1 + urb->num_sgs;
> > + else if (usb_pipein(urb->pipe) && priv->sgl)
> > + iovnum = 1 + priv->num_urbs;
> > else
> > iovnum = 2;
> > @@ -192,6 +203,15 @@ static int stub_send_ret_submit(struct stub_device *sdev)
> > setup_ret_submit_pdu(&pdu_header, urb);
> > usbip_dbg_stub_tx("setup txdata seqnum: %d\n",
> > pdu_header.base.seqnum);
> > +
> > + if (priv->sgl) {
> > + for (i = 0; i < priv->num_urbs; i++)
> > + actual_length += priv->urbs[i]->actual_length;
> > +
> > + pdu_header.u.ret_submit.status = priv->urb_status;
> > + pdu_header.u.ret_submit.actual_length = actual_length;
> > + }
> > +
> > usbip_header_correct_endian(&pdu_header, 1);
> > iov[iovnum].iov_base = &pdu_header;
> > @@ -200,12 +220,47 @@ static int stub_send_ret_submit(struct stub_device *sdev)
> > txsize += sizeof(pdu_header);
> > /* 2. setup transfer buffer */
> > - if (usb_pipein(urb->pipe) &&
> > + if (usb_pipein(urb->pipe) && priv->sgl) {
> > + /* If the server split a single SG request into several
> > + * URBs because the server's HCD doesn't support SG,
> > + * reassemble the split URB buffers into a single
> > + * return command.
> > + */
> > + for (i = 0; i < priv->num_urbs; i++) {
> > + iov[iovnum].iov_base =
> > + priv->urbs[i]->transfer_buffer;
> > + iov[iovnum].iov_len =
> > + priv->urbs[i]->actual_length;
> > + iovnum++;
> > + }
> > + txsize += actual_length;
> > + } else if (usb_pipein(urb->pipe) &&
> > usb_pipetype(urb->pipe) != PIPE_ISOCHRONOUS &&
> > urb->actual_length > 0) {
> > - iov[iovnum].iov_base = urb->transfer_buffer;
> > - iov[iovnum].iov_len = urb->actual_length;
> > - iovnum++;
> > + if (urb->num_sgs) {
> > + unsigned int copy = urb->actual_length;
> > + int size;
> > +
> > + for_each_sg(urb->sg, sg, urb->num_sgs, i) {
> > + if (copy == 0)
> > + break;
> > +
> > + if (copy < sg->length)
> > + size = copy;
> > + else
> > + size = sg->length;
> > +
> > + iov[iovnum].iov_base = sg_virt(sg);
> > + iov[iovnum].iov_len = size;
> > +
> > + iovnum++;
> > + copy -= size;
> > + }
> > + } else {
> > + iov[iovnum].iov_base = urb->transfer_buffer;
> > + iov[iovnum].iov_len = urb->actual_length;
> > + iovnum++;
> > + }
> > txsize += urb->actual_length;
> > } else if (usb_pipein(urb->pipe) &&
> > usb_pipetype(urb->pipe) == PIPE_ISOCHRONOUS) {
> > diff --git a/drivers/usb/usbip/usbip_common.c b/drivers/usb/usbip/usbip_common.c
> > index 45da3e01c7b0..6532d68e8808 100644
> > --- a/drivers/usb/usbip/usbip_common.c
> > +++ b/drivers/usb/usbip/usbip_common.c
> > @@ -680,8 +680,12 @@ EXPORT_SYMBOL_GPL(usbip_pad_iso);
> > /* some members of urb must be substituted before. */
> > int usbip_recv_xbuff(struct usbip_device *ud, struct urb *urb)
> > {
> > - int ret;
> > + struct scatterlist *sg;
> > + int ret = 0;
> > + int recv;
> > int size;
> > + int copy;
> > + int i;
> > if (ud->side == USBIP_STUB || ud->side == USBIP_VUDC) {
> > /* the direction of urb must be OUT. */
> > @@ -701,29 +705,48 @@ int usbip_recv_xbuff(struct usbip_device *ud, struct urb *urb)
> > if (!(size > 0))
> > return 0;
> > - if (size > urb->transfer_buffer_length) {
> > + if (size > urb->transfer_buffer_length)
> > /* should not happen, probably malicious packet */
> > - if (ud->side == USBIP_STUB) {
> > - usbip_event_add(ud, SDEV_EVENT_ERROR_TCP);
> > - return 0;
> > - } else {
> > - usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);
> > - return -EPIPE;
> > - }
> > - }
> > + goto error;
> > - ret = usbip_recv(ud->tcp_socket, urb->transfer_buffer, size);
> > - if (ret != size) {
> > - dev_err(&urb->dev->dev, "recv xbuf, %d\n", ret);
> > - if (ud->side == USBIP_STUB || ud->side == USBIP_VUDC) {
> > - usbip_event_add(ud, SDEV_EVENT_ERROR_TCP);
> > - } else {
> > - usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);
> > - return -EPIPE;
> > + if (urb->num_sgs) {
> > + copy = size;
> > + for_each_sg(urb->sg, sg, urb->num_sgs, i) {
> > + int recv_size;
> > +
> > + if (copy < sg->length)
> > + recv_size = copy;
> > + else
> > + recv_size = sg->length;
> > +
> > + recv = usbip_recv(ud->tcp_socket, sg_virt(sg),
> > + recv_size);
> > +
> > + if (recv != recv_size)
> > + goto error;
> > +
> > + copy -= recv;
> > + ret += recv;
> > }
> > +
> > + if (ret != size)
> > + goto error;
> > + } else {
> > + ret = usbip_recv(ud->tcp_socket, urb->transfer_buffer, size);
> > + if (ret != size)
> > + goto error;
> > }
> > return ret;
> > +
> > +error:
> > + dev_err(&urb->dev->dev, "recv xbuf, %d\n", ret);
> > + if (ud->side == USBIP_STUB || ud->side == USBIP_VUDC)
> > + usbip_event_add(ud, SDEV_EVENT_ERROR_TCP);
> > + else
> > + usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);
> > +
> > + return -EPIPE;
> > }
> > EXPORT_SYMBOL_GPL(usbip_recv_xbuff);
> > diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
> > index 000ab7225717..585a84d319bd 100644
> > --- a/drivers/usb/usbip/vhci_hcd.c
> > +++ b/drivers/usb/usbip/vhci_hcd.c
> > @@ -697,7 +697,8 @@ static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
> > }
> > vdev = &vhci_hcd->vdev[portnum-1];
> > - if (!urb->transfer_buffer && urb->transfer_buffer_length) {
> > + if (!urb->transfer_buffer && !urb->num_sgs &&
> > + urb->transfer_buffer_length) {
> > dev_dbg(dev, "Null URB transfer buffer\n");
> > return -EINVAL;
> > }
> > @@ -1143,6 +1144,15 @@ static int vhci_setup(struct usb_hcd *hcd)
> > hcd->speed = HCD_USB3;
> > hcd->self.root_hub->speed = USB_SPEED_SUPER;
> > }
> > +
> > + /*
> > + * Support SG.
> > + * sg_tablesize is an arbitrary value to alleviate memory pressure
> > + * on the host.
> > + */
> > + hcd->self.sg_tablesize = 32;
> > + hcd->self.no_sg_constraint = 1;
> > +
> > return 0;
> > }
> > diff --git a/drivers/usb/usbip/vhci_rx.c b/drivers/usb/usbip/vhci_rx.c
> > index 44cd64518925..33f8972ba842 100644
> > --- a/drivers/usb/usbip/vhci_rx.c
> > +++ b/drivers/usb/usbip/vhci_rx.c
> > @@ -90,6 +90,9 @@ static void vhci_recv_ret_submit(struct vhci_device *vdev,
> > if (usbip_dbg_flag_vhci_rx)
> > usbip_dump_urb(urb);
> > + if (urb->num_sgs)
> > + urb->transfer_flags &= ~URB_DMA_MAP_SG;
> > +

I will remove this modification. Please see below comment.

> > usbip_dbg_vhci_rx("now giveback urb %u\n", pdu->base.seqnum);
> > spin_lock_irqsave(&vhci->lock, flags);
> > diff --git a/drivers/usb/usbip/vhci_tx.c b/drivers/usb/usbip/vhci_tx.c
> > index 2fa26d0578d7..f9c92e042874 100644
> > --- a/drivers/usb/usbip/vhci_tx.c
> > +++ b/drivers/usb/usbip/vhci_tx.c
> > @@ -5,6 +5,7 @@
> > #include <linux/kthread.h>
> > #include <linux/slab.h>
> > +#include <linux/scatterlist.h>
> > #include "usbip_common.h"
> > #include "vhci.h"
> > @@ -50,19 +51,23 @@ static struct vhci_priv *dequeue_from_priv_tx(struct vhci_device *vdev)
> > static int vhci_send_cmd_submit(struct vhci_device *vdev)
> > {
> > + struct usbip_iso_packet_descriptor *iso_buffer = NULL;
> > struct vhci_priv *priv = NULL;
> > + struct scatterlist *sg;
> > struct msghdr msg;
> > - struct kvec iov[3];
> > + struct kvec *iov;
> > size_t txsize;
> > size_t total_size = 0;
> > + int iovnum;
> > + int err = -ENOMEM;
> > + int i;
> > while ((priv = dequeue_from_priv_tx(vdev)) != NULL) {
> > int ret;
> > struct urb *urb = priv->urb;
> > struct usbip_header pdu_header;
> > - struct usbip_iso_packet_descriptor *iso_buffer = NULL;
> > txsize = 0;
> > memset(&pdu_header, 0, sizeof(pdu_header));
> > @@ -72,18 +77,45 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
> > usbip_dbg_vhci_tx("setup txdata urb seqnum %lu\n",
> > priv->seqnum);
> > + if (urb->num_sgs && usb_pipeout(urb->pipe))
> > + iovnum = 2 + urb->num_sgs;
> > + else
> > + iovnum = 3;
> > +
> > + if (urb->num_sgs)
> > + urb->transfer_flags |= URB_DMA_MAP_SG;
> > +
>
> Move this down after the kcalloc()

You are right. Setting flag should be a part of "setup usbip_header"
And I think the flag should be set inside setup_cmd_submit_pdu().

> > + iov = kcalloc(iovnum, sizeof(*iov), GFP_KERNEL);
> > + if (!iov) {
> > + usbip_event_add(&vdev->ud, SDEV_EVENT_ERROR_MALLOC);
> > + return -ENOMEM;
> > + }
> > +
> > /* 1. setup usbip_header */
> > setup_cmd_submit_pdu(&pdu_header, urb);

The flag should be set in this function.
And I think that it is better to manipulate the flag of pdu_header
rather than modify the urb->transfer_flags directly because if I set
urb->transfer_flags directly, vhci_rx should clear URB_DMA_MAP_SG
flag in order to avoid DMA unmap in HCD.

If I set flag of pdu_header, I can remove clearing URB_DMA_MAP_SG
flag in vhci_recv_ret_submit() that I newly added in v6.

Regards
Suwan Kim

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