linux-stable.git/drivers/char/virtio_console.c, branch linux-3.16.y

virtio_console: allocate inbufs in add_port() only if it is needed

2019-12-19T15:59:02+00:00

commit d791cfcbf98191122af70b053a21075cb450d119 upstream.

When we hot unplug a virtserialport and then try to hot plug again,
it fails:

(qemu) chardev-add socket,id=serial0,path=/tmp/serial0,server,nowait
(qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\
                  chardev=serial0,id=serial0,name=serial0
(qemu) device_del serial0
(qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\
                  chardev=serial0,id=serial0,name=serial0
kernel error:
  virtio-ports vport2p2: Error allocating inbufs
qemu error:
  virtio-serial-bus: Guest failure in adding port 2 for device \
                     virtio-serial0.0

This happens because buffers for the in_vq are allocated when the port is
added but are not released when the port is unplugged.

They are only released when virtconsole is removed (see a7a69ec0d8e4)

To avoid the problem and to be symmetric, we could allocate all the buffers
in init_vqs() as they are released in remove_vqs(), but it sounds like
a waste of memory.

Rather than that, this patch changes add_port() logic to ignore ENOSPC
error in fill_queue(), which means queue has already been filled.

Fixes: a7a69ec0d8e4 ("virtio_console: free buffers after reset")
Cc: mst@redhat.com
Signed-off-by: Laurent Vivier 
Signed-off-by: Michael S. Tsirkin 
Signed-off-by: Ben Hutchings

virtio_console: reset on out of memory

2018-10-21T07:45:45+00:00

commit 5c60300d68da32ca77f7f978039dc72bfc78b06b upstream.

When out of memory and we can't add ctrl vq buffers,
probe fails. Unfortunately the error handling is
out of spec: it calls del_vqs without bothering
to reset the device first.

To fix, call the full cleanup function in this case.

Signed-off-by: Michael S. Tsirkin 
Signed-off-by: Ben Hutchings

virtio_console: move removal code

2018-10-21T07:45:45+00:00

commit aa44ec867030a72e8aa127977e37dec551d8df19 upstream.

Will make it reusable for error handling.

Signed-off-by: Michael S. Tsirkin 
Signed-off-by: Ben Hutchings

virtio_console: drop custom control queue cleanup

2018-10-21T07:45:45+00:00

commit 61a8950c5c5708cf2068b29ffde94e454e528208 upstream.

We now cleanup all VQs on device removal - no need
to handle the control VQ specially.

Signed-off-by: Michael S. Tsirkin 
Signed-off-by: Ben Hutchings

virtio_console: free buffers after reset

2018-10-21T07:45:44+00:00

commit a7a69ec0d8e4a58be7db88d33cbfa2912807bb2b upstream.

Console driver is out of spec. The spec says:
	A driver MUST NOT decrement the available idx on a live
	virtqueue (ie. there is no way to “unexpose” buffers).
and it does exactly that by trying to detach unused buffers
without doing a device reset first.

Defer detaching the buffers until device unplug.

Of course this means we might get an interrupt for
a vq without an attached port now. Handle that by
discarding the consumed buffer.

Reported-by: Tiwei Bie 
Fixes: b3258ff1d6 ("virtio: Decrement avail idx on buffer detach")
Signed-off-by: Michael S. Tsirkin 
Signed-off-by: Ben Hutchings

virtio_console: don't tie bufs to a vq

2018-10-21T07:45:44+00:00

commit 2855b33514d290c51d52d94e25d3ef942cd4d578 upstream.

an allocated buffer doesn't need to be tied to a vq -
only vq->vdev is ever used. Pass the function the
just what it needs - the vdev.

Signed-off-by: Michael S. Tsirkin 
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings

virtio_console: fix uninitialized variable use

2017-07-18T17:40:32+00:00

commit 2055997f983c6db7b5c3940ce5f8f822657d5bc3 upstream.

We try to disable callbacks on c_ivq even without multiport
even though that vq is not initialized in this configuration.

Fixes: c743d09dbd01 ("virtio: console: Disable callbacks for virtqueues at start of S4 freeze")
Suggested-by: Mike Galbraith 
Signed-off-by: Michael S. Tsirkin 
Signed-off-by: Ben Hutchings

virtio-console: avoid DMA from stack

2017-06-05T20:17:22+00:00

commit c4baad50297d84bde1a7ad45e50c73adae4a2192 upstream.

put_chars() stuffs the buffer it gets into an sg, but that buffer may be
on the stack. This breaks with CONFIG_VMAP_STACK=y (for me, it
manifested as printks getting turned into NUL bytes).

Signed-off-by: Omar Sandoval 
Signed-off-by: Michael S. Tsirkin 
Reviewed-by: Amit Shah 
Signed-off-by: Ben Hutchings

virtio: console: Unlock vqs while freeing buffers

2017-02-23T03:54:26+00:00

commit 34563769e438d2881f62cf4d9badc4e589ac0ec0 upstream.

Commit c6017e793b93 ("virtio: console: add locks around buffer removal
in port unplug path") added locking around the freeing of buffers in the
vq. However, when free_buf() is called with can_sleep = true and rproc
is enabled, it calls dma_free_coherent() directly, requiring interrupts
to be enabled. Currently a WARNING is triggered due to the spin locking
around free_buf, with a call stack like this:

WARNING: CPU: 3 PID: 121 at ./include/linux/dma-mapping.h:433
free_buf+0x1a8/0x288
Call Trace:
[<8040c538>] show_stack+0x74/0xc0
[<80757240>] dump_stack+0xd0/0x110
[<80430d98>] __warn+0xfc/0x130
[<80430ee0>] warn_slowpath_null+0x2c/0x3c
[<807e7c6c>] free_buf+0x1a8/0x288
[<807ea590>] remove_port_data+0x50/0xac
[<807ea6a0>] unplug_port+0xb4/0x1bc
[<807ea858>] virtcons_remove+0xb0/0xfc
[<807b6734>] virtio_dev_remove+0x58/0xc0
[<807f918c>] __device_release_driver+0xac/0x134
[<807f924c>] device_release_driver+0x38/0x50
[<807f7edc>] bus_remove_device+0xfc/0x130
[<807f4b74>] device_del+0x17c/0x21c
[<807f4c38>] device_unregister+0x24/0x38
[<807b6b50>] unregister_virtio_device+0x28/0x44

Fix this by restructuring the loops to allow the locks to only be taken
where it is necessary to protect the vqs, and release it while the
buffer is being freed.

Fixes: c6017e793b93 ("virtio: console: add locks around buffer removal in port unplug path")
Signed-off-by: Matt Redfearn 
Signed-off-by: Michael S. Tsirkin 
Signed-off-by: Ben Hutchings

virtio_console: avoid config access from irq

2015-03-30T10:10:55+00:00

commit eeb8a7e8bb123e84daeef84f5a2eab99ad2839a2 upstream.

when multiport is off, virtio console invokes config access from irq
context, config access is blocking on s390.
Fix this up by scheduling work from config irq - similar to what we do
for multiport configs.

Signed-off-by: Michael S. Tsirkin 
Reviewed-by: Amit Shah 
Signed-off-by: Rusty Russell 
Signed-off-by: Luis Henriques