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uio_hv_generic: defer opening vmbus until first use
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This fixes two design flaws in hv_uio_generic.

Since hv_uio_probe is called from vmbus_probe with lock held
it potentially can cause sleep in an atomic section because
vmbus_open will wait for response from host.

The hv_uio_generic driver could not handle applications
exiting and restarting because the vmbus channel was
persistent.  Change the semantics so that the buffers are
allocated on probe, but not attached to host until
device is opened.

Signed-off-by: Stephen Hemminger <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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@shemminger @gregkh
shemminger authored and gregkh committed Sep 25, 2018
1 parent 9da197f commit cdfa835
Showing 1 changed file with 74 additions and 30 deletions.
104 changes: 74 additions & 30 deletions drivers/uio/uio_hv_generic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@ enum hv_uio_map {
struct hv_uio_private_data {
struct uio_info info;
struct hv_device *device;
atomic_t refcnt;

void *recv_buf;
u32 recv_gpadl;
Expand Down Expand Up @@ -128,12 +129,10 @@ static int hv_uio_ring_mmap(struct file *filp, struct kobject *kobj,
{
struct vmbus_channel *channel
= container_of(kobj, struct vmbus_channel, kobj);
struct hv_device *dev = channel->primary_channel->device_obj;
u16 q_idx = channel->offermsg.offer.sub_channel_index;
void *ring_buffer = page_address(channel->ringbuffer_page);

dev_dbg(&dev->device, "mmap channel %u pages %#lx at %#lx\n",
q_idx, vma_pages(vma), vma->vm_pgoff);
if (channel->state != CHANNEL_OPENED_STATE)
return -ENODEV;

return vm_iomap_memory(vma, virt_to_phys(ring_buffer),
channel->ringbuffer_pagecount << PAGE_SHIFT);
Expand Down Expand Up @@ -176,57 +175,103 @@ hv_uio_new_channel(struct vmbus_channel *new_sc)
}
}

/* free the reserved buffers for send and receive */
static void
hv_uio_cleanup(struct hv_device *dev, struct hv_uio_private_data *pdata)
{
if (pdata->send_gpadl)
if (pdata->send_gpadl) {
vmbus_teardown_gpadl(dev->channel, pdata->send_gpadl);
vfree(pdata->send_buf);
pdata->send_gpadl = 0;
vfree(pdata->send_buf);
}

if (pdata->recv_gpadl)
if (pdata->recv_gpadl) {
vmbus_teardown_gpadl(dev->channel, pdata->recv_gpadl);
vfree(pdata->recv_buf);
pdata->recv_gpadl = 0;
vfree(pdata->recv_buf);
}
}

/* VMBus primary channel is opened on first use */
static int
hv_uio_open(struct uio_info *info, struct inode *inode)
{
struct hv_uio_private_data *pdata
= container_of(info, struct hv_uio_private_data, info);
struct hv_device *dev = pdata->device;
int ret;

if (atomic_inc_return(&pdata->refcnt) != 1)
return 0;

ret = vmbus_connect_ring(dev->channel,
hv_uio_channel_cb, dev->channel);

if (ret == 0)
dev->channel->inbound.ring_buffer->interrupt_mask = 1;
else
atomic_dec(&pdata->refcnt);

return ret;
}

/* VMBus primary channel is closed on last close */
static int
hv_uio_release(struct uio_info *info, struct inode *inode)
{
struct hv_uio_private_data *pdata
= container_of(info, struct hv_uio_private_data, info);
struct hv_device *dev = pdata->device;
int ret = 0;

if (atomic_dec_and_test(&pdata->refcnt))
ret = vmbus_disconnect_ring(dev->channel);

return ret;
}

static int
hv_uio_probe(struct hv_device *dev,
const struct hv_vmbus_device_id *dev_id)
{
struct vmbus_channel *channel = dev->channel;
struct hv_uio_private_data *pdata;
void *ring_buffer;
int ret;

/* Communicating with host has to be via shared memory not hypercall */
if (!channel->offermsg.monitor_allocated) {
dev_err(&dev->device, "vmbus channel requires hypercall\n");
return -ENOTSUPP;
}

pdata = kzalloc(sizeof(*pdata), GFP_KERNEL);
if (!pdata)
return -ENOMEM;

ret = vmbus_open(dev->channel, HV_RING_SIZE * PAGE_SIZE,
HV_RING_SIZE * PAGE_SIZE, NULL, 0,
hv_uio_channel_cb, dev->channel);
ret = vmbus_alloc_ring(channel, HV_RING_SIZE * PAGE_SIZE,
HV_RING_SIZE * PAGE_SIZE);
if (ret)
goto fail;

/* Communicating with host has to be via shared memory not hypercall */
if (!dev->channel->offermsg.monitor_allocated) {
dev_err(&dev->device, "vmbus channel requires hypercall\n");
ret = -ENOTSUPP;
goto fail_close;
}

dev->channel->inbound.ring_buffer->interrupt_mask = 1;
set_channel_read_mode(dev->channel, HV_CALL_ISR);
set_channel_read_mode(channel, HV_CALL_ISR);

/* Fill general uio info */
pdata->info.name = "uio_hv_generic";
pdata->info.version = DRIVER_VERSION;
pdata->info.irqcontrol = hv_uio_irqcontrol;
pdata->info.open = hv_uio_open;
pdata->info.release = hv_uio_release;
pdata->info.irq = UIO_IRQ_CUSTOM;
atomic_set(&pdata->refcnt, 0);

/* mem resources */
pdata->info.mem[TXRX_RING_MAP].name = "txrx_rings";
ring_buffer = page_address(channel->ringbuffer_page);
pdata->info.mem[TXRX_RING_MAP].addr
= (uintptr_t)virt_to_phys(page_address(dev->channel->ringbuffer_page));
= (uintptr_t)virt_to_phys(ring_buffer);
pdata->info.mem[TXRX_RING_MAP].size
= dev->channel->ringbuffer_pagecount << PAGE_SHIFT;
= channel->ringbuffer_pagecount << PAGE_SHIFT;
pdata->info.mem[TXRX_RING_MAP].memtype = UIO_MEM_IOVA;

pdata->info.mem[INT_PAGE_MAP].name = "int_page";
Expand All @@ -247,7 +292,7 @@ hv_uio_probe(struct hv_device *dev,
goto fail_close;
}

ret = vmbus_establish_gpadl(dev->channel, pdata->recv_buf,
ret = vmbus_establish_gpadl(channel, pdata->recv_buf,
RECV_BUFFER_SIZE, &pdata->recv_gpadl);
if (ret)
goto fail_close;
Expand All @@ -261,14 +306,13 @@ hv_uio_probe(struct hv_device *dev,
pdata->info.mem[RECV_BUF_MAP].size = RECV_BUFFER_SIZE;
pdata->info.mem[RECV_BUF_MAP].memtype = UIO_MEM_VIRTUAL;


pdata->send_buf = vzalloc(SEND_BUFFER_SIZE);
if (pdata->send_buf == NULL) {
ret = -ENOMEM;
goto fail_close;
}

ret = vmbus_establish_gpadl(dev->channel, pdata->send_buf,
ret = vmbus_establish_gpadl(channel, pdata->send_buf,
SEND_BUFFER_SIZE, &pdata->send_gpadl);
if (ret)
goto fail_close;
Expand All @@ -290,10 +334,10 @@ hv_uio_probe(struct hv_device *dev,
goto fail_close;
}

vmbus_set_chn_rescind_callback(dev->channel, hv_uio_rescind);
vmbus_set_sc_create_callback(dev->channel, hv_uio_new_channel);
vmbus_set_chn_rescind_callback(channel, hv_uio_rescind);
vmbus_set_sc_create_callback(channel, hv_uio_new_channel);

ret = sysfs_create_bin_file(&dev->channel->kobj, &ring_buffer_bin_attr);
ret = sysfs_create_bin_file(&channel->kobj, &ring_buffer_bin_attr);
if (ret)
dev_notice(&dev->device,
"sysfs create ring bin file failed; %d\n", ret);
Expand All @@ -304,7 +348,6 @@ hv_uio_probe(struct hv_device *dev,

fail_close:
hv_uio_cleanup(dev, pdata);
vmbus_close(dev->channel);
fail:
kfree(pdata);

Expand All @@ -322,7 +365,8 @@ hv_uio_remove(struct hv_device *dev)
uio_unregister_device(&pdata->info);
hv_uio_cleanup(dev, pdata);
hv_set_drvdata(dev, NULL);
vmbus_close(dev->channel);

vmbus_free_ring(dev->channel);
kfree(pdata);
return 0;
}
Expand Down

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