linux-stable.git/drivers/vhost/vhost.c, branch v5.8

Merge branch 'akpm' (patches from Andrew)

2020-06-11T20:25:53+00:00

Merge some more updates from Andrew Morton:

 - various hotfixes and minor things

 - hch's use_mm/unuse_mm clearnups

Subsystems affected by this patch series: mm/hugetlb, scripts, kcov,
lib, nilfs, checkpatch, lib, mm/debug, ocfs2, lib, misc.

* emailed patches from Andrew Morton :
  kernel: set USER_DS in kthread_use_mm
  kernel: better document the use_mm/unuse_mm API contract
  kernel: move use_mm/unuse_mm to kthread.c
  kernel: move use_mm/unuse_mm to kthread.c
  stacktrace: cleanup inconsistent variable type
  lib: test get_count_order/long in test_bitops.c
  mm: add comments on pglist_data zones
  ocfs2: fix spelling mistake and grammar
  mm/debug_vm_pgtable: fix kernel crash by checking for THP support
  lib: fix bitmap_parse() on 64-bit big endian archs
  checkpatch: correct check for kernel parameters doc
  nilfs2: fix null pointer dereference at nilfs_segctor_do_construct()
  lib/lz4/lz4_decompress.c: document deliberate use of `&'
  kcov: check kcov_softirq in kcov_remote_stop()
  scripts/spelling: add a few more typos
  khugepaged: selftests: fix timeout condition in wait_for_scan()

kernel: set USER_DS in kthread_use_mm

2020-06-11T02:14:18+00:00

Some architectures like arm64 and s390 require USER_DS to be set for
kernel threads to access user address space, which is the whole purpose of
kthread_use_mm, but other like x86 don't.  That has lead to a huge mess
where some callers are fixed up once they are tested on said
architectures, while others linger around and yet other like io_uring try
to do "clever" optimizations for what usually is just a trivial asignment
to a member in the thread_struct for most architectures.

Make kthread_use_mm set USER_DS, and kthread_unuse_mm restore to the
previous value instead.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Andrew Morton 
Tested-by: Jens Axboe 
Reviewed-by: Jens Axboe 
Acked-by: Michael S. Tsirkin 
Cc: Alex Deucher 
Cc: Al Viro 
Cc: Felipe Balbi 
Cc: Felix Kuehling 
Cc: Jason Wang 
Cc: Zhenyu Wang 
Cc: Zhi Wang 
Cc: Greg Kroah-Hartman 
Link: http://lkml.kernel.org/r/20200404094101.672954-7-hch@lst.de
Signed-off-by: Linus Torvalds

kernel: better document the use_mm/unuse_mm API contract

2020-06-11T02:14:18+00:00

Switch the function documentation to kerneldoc comments, and add
WARN_ON_ONCE asserts that the calling thread is a kernel thread and does
not have ->mm set (or has ->mm set in the case of unuse_mm).

Also give the functions a kthread_ prefix to better document the use case.

[hch@lst.de: fix a comment typo, cover the newly merged use_mm/unuse_mm caller in vfio]
  Link: http://lkml.kernel.org/r/20200416053158.586887-3-hch@lst.de
[sfr@canb.auug.org.au: powerpc/vas: fix up for {un}use_mm() rename]
  Link: http://lkml.kernel.org/r/20200422163935.5aa93ba5@canb.auug.org.au

Signed-off-by: Christoph Hellwig 
Signed-off-by: Stephen Rothwell 
Signed-off-by: Andrew Morton 
Tested-by: Jens Axboe 
Reviewed-by: Jens Axboe 
Acked-by: Felix Kuehling 
Acked-by: Greg Kroah-Hartman  [usb]
Acked-by: Haren Myneni 
Cc: Alex Deucher 
Cc: Al Viro 
Cc: Felipe Balbi 
Cc: Jason Wang 
Cc: "Michael S. Tsirkin" 
Cc: Zhenyu Wang 
Cc: Zhi Wang 
Link: http://lkml.kernel.org/r/20200404094101.672954-6-hch@lst.de
Signed-off-by: Linus Torvalds

kernel: move use_mm/unuse_mm to kthread.c

2020-06-11T02:14:18+00:00

Patch series "improve use_mm / unuse_mm", v2.

This series improves the use_mm / unuse_mm interface by better documenting
the assumptions, and my taking the set_fs manipulations spread over the
callers into the core API.

This patch (of 3):

Use the proper API instead.

Link: http://lkml.kernel.org/r/20200404094101.672954-1-hch@lst.de

These helpers are only for use with kernel threads, and I will tie them
more into the kthread infrastructure going forward.  Also move the
prototypes to kthread.h - mmu_context.h was a little weird to start with
as it otherwise contains very low-level MM bits.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Andrew Morton 
Tested-by: Jens Axboe 
Reviewed-by: Jens Axboe 
Acked-by: Felix Kuehling 
Cc: Alex Deucher 
Cc: Al Viro 
Cc: Felipe Balbi 
Cc: Jason Wang 
Cc: "Michael S. Tsirkin" 
Cc: Zhenyu Wang 
Cc: Zhi Wang 
Cc: Greg Kroah-Hartman 
Link: http://lkml.kernel.org/r/20200404094101.672954-1-hch@lst.de
Link: http://lkml.kernel.org/r/20200416053158.586887-1-hch@lst.de
Link: http://lkml.kernel.org/r/20200404094101.672954-5-hch@lst.de
Signed-off-by: Linus Torvalds

Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

2020-06-10T20:42:09+00:00

Pull virtio updates from Michael Tsirkin:

 - virtio-mem: paravirtualized memory hotplug

 - support doorbell mapping for vdpa

 - config interrupt support in ifc

 - fixes all over the place

* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost: (40 commits)
  vhost/test: fix up after API change
  virtio_mem: convert device block size into 64bit
  virtio-mem: drop unnecessary initialization
  ifcvf: implement config interrupt in IFCVF
  vhost: replace -1 with VHOST_FILE_UNBIND in ioctls
  vhost_vdpa: Support config interrupt in vdpa
  ifcvf: ignore continuous setting same status value
  virtio-mem: Don't rely on implicit compiler padding for requests
  virtio-mem: Try to unplug the complete online memory block first
  virtio-mem: Use -ETXTBSY as error code if the device is busy
  virtio-mem: Unplug subblocks right-to-left
  virtio-mem: Drop manual check for already present memory
  virtio-mem: Add parent resource for all added "System RAM"
  virtio-mem: Better retry handling
  virtio-mem: Offline and remove completely unplugged memory blocks
  mm/memory_hotplug: Introduce offline_and_remove_memory()
  virtio-mem: Allow to offline partially unplugged memory blocks
  mm: Allow to offline unmovable PageOffline() pages via MEM_GOING_OFFLINE
  virtio-mem: Paravirtualized memory hotunplug part 2
  virtio-mem: Paravirtualized memory hotunplug part 1
  ...

vhost: convert get_user_pages() --> pin_user_pages()

2020-06-08T18:05:57+00:00

This code was using get_user_pages*(), in approximately a "Case 5"
scenario (accessing the data within a page), using the categorization
from [1].  That means that it's time to convert the get_user_pages*() +
put_page() calls to pin_user_pages*() + unpin_user_pages() calls.

There is some helpful background in [2]: basically, this is a small part
of fixing a long-standing disconnect between pinning pages, and file
systems' use of those pages.

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
    https://lwn.net/Articles/807108/

Signed-off-by: John Hubbard 
Signed-off-by: Andrew Morton 
Reviewed-by: Jan Kara 
Acked-by: Michael S. Tsirkin 
Acked-by: Pankaj Gupta 
Cc: Jason Wang 
Cc: Dave Chinner 
Cc: Jérôme Glisse 
Cc: Jonathan Corbet 
Cc: Souptick Joarder 
Cc: Vlastimil Babka 
Link: http://lkml.kernel.org/r/20200529234309.484480-3-jhubbard@nvidia.com
Signed-off-by: Linus Torvalds

vhost: replace -1 with VHOST_FILE_UNBIND in ioctls

2020-06-06T20:26:27+00:00

This commit replaces -1 with VHOST_FILE_UNBIND in ioctls since
we have added such a macro in the uapi header for vdpa_host.

Signed-off-by: Zhu Lingshan 
Acked-by: Jason Wang 
Link: https://lore.kernel.org/r/1591352835-22441-5-git-send-email-lingshan.zhu@intel.com
Signed-off-by: Michael S. Tsirkin

vhost: (cosmetic) remove a superfluous variable initialisation

2020-06-04T19:36:51+00:00

Even the compiler is able to figure out that in this case the
initialisation is superfluous.

Signed-off-by: Guennadi Liakhovetski 
Link: https://lore.kernel.org/r/20200527180541.5570-3-guennadi.liakhovetski@linux.intel.com
Signed-off-by: Michael S. Tsirkin

vhost: use mmgrab() instead of mmget() for non worker device

2020-06-04T19:36:51+00:00

For the device that doesn't use vhost worker and use_mm(), mmget() is
too heavy weight and it may brings troubles for implementing mmap()
support for vDPA device.

This is because, an reference to the address space was held via
mm_get() in vhost_dev_set_owner() and an reference to the file was
held in mmap(). This means when process exits, the mm can not be
released thus we can not release the file.

This patch tries to use mmgrab() instead of mmget(), which allows the
address space to be destroy in process exit without releasing the mm
structure itself. This is sufficient for vDPA device which pin user
pages and does not depend on the address space to work.

Signed-off-by: Jason Wang 
Link: https://lore.kernel.org/r/20200529080303.15449-3-jasowang@redhat.com
Signed-off-by: Michael S. Tsirkin

vhost: allow device that does not depend on vhost worker

2020-06-04T19:36:51+00:00

vDPA device currently relays the eventfd via vhost worker. This is
inefficient due the latency of wakeup and scheduling, so this patch
tries to introduce a use_worker attribute for the vhost device. When
use_worker is not set with vhost_dev_init(), vhost won't try to
allocate a worker thread and the vhost_poll will be processed directly
in the wakeup function.

This help for vDPA since it reduces the latency caused by vhost worker.

In my testing, it saves 0.2 ms in pings between VMs on a mutual host.

Signed-off-by: Zhu Lingshan 
Signed-off-by: Jason Wang 
Link: https://lore.kernel.org/r/20200529080303.15449-2-jasowang@redhat.com
Signed-off-by: Michael S. Tsirkin