Commit 550ddadcc758 ("tty: hvc: hvc_write() may sleep") broke the
termination condition in case the driver stops accepting characters.
This can result in unnecessary polling of the busy driver.

Restore it by testing the hvc_push return code.

Tested-by: Matteo Croce <mcroce@redhat.com>
Tested-by: Jason Gunthorpe <jgg@mellanox.com>
Tested-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit ec97eaad1383 ("tty: hvc: hvc_poll() break hv read loop")
removes get_chars batching entirely, which slows down large console
operations like paste -- virtio console "feels worse than a 9600 baud
serial line," reports Matteo.

This adds back batching in a more latency friendly way. If the caller
can sleep then we try to fill the entire flip buffer, releasing the
lock and scheduling between each iteration. If it can not sleep, then
batches are limited to 128 bytes. Matteo confirms this fixes the
performance problem.

Latency testing the powerpc OPAL console with OpenBMC UART with a
large paste shows about 0.25ms latency, which seems reasonable. 10ms
latencies were typical for this case before the latency breaking work,
so we still see most of the benefit.

  kopald-1204    0d.h.    5us : hvc_poll <-hvc_handle_interrupt
  kopald-1204    0d.h.    5us : __hvc_poll <-hvc_handle_interrupt
  kopald-1204    0d.h.    5us : _raw_spin_lock_irqsave <-__hvc_poll
  kopald-1204    0d.h.    5us : tty_port_tty_get <-__hvc_poll
  kopald-1204    0d.h.    6us : _raw_spin_lock_irqsave <-tty_port_tty_get
  kopald-1204    0d.h.    6us : _raw_spin_unlock_irqrestore <-tty_port_tty_get
  kopald-1204    0d.h.    6us : tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.    7us : __tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.    7us+: opal_get_chars <-__hvc_poll
  kopald-1204    0d.h.   36us : tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.   36us : __tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.   36us+: opal_get_chars <-__hvc_poll
  kopald-1204    0d.h.   65us : tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.   65us : __tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.   66us+: opal_get_chars <-__hvc_poll
  kopald-1204    0d.h.   94us : tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.   95us : __tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.   95us+: opal_get_chars <-__hvc_poll
  kopald-1204    0d.h.  124us : tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.  124us : __tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.  125us+: opal_get_chars <-__hvc_poll
  kopald-1204    0d.h.  154us : tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.  154us : __tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.  154us+: opal_get_chars <-__hvc_poll
  kopald-1204    0d.h.  183us : tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.  184us : __tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.  184us+: opal_get_chars <-__hvc_poll
  kopald-1204    0d.h.  213us : tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.  213us : __tty_buffer_request_room <-__hvc_poll
  kopald-1204    0d.h.  213us+: opal_get_chars <-__hvc_poll
  kopald-1204    0d.h.  242us : _raw_spin_unlock_irqrestore <-__hvc_poll
  kopald-1204    0d.h.  242us : tty_flip_buffer_push <-__hvc_poll
  kopald-1204    0d.h.  243us : queue_work_on <-tty_flip_buffer_push
  kopald-1204    0d.h.  243us : tty_kref_put <-__hvc_poll
  kopald-1204    0d.h.  243us : hvc_kick <-hvc_handle_interrupt
  kopald-1204    0d.h.  243us : wake_up_process <-hvc_kick
  kopald-1204    0d.h.  244us : try_to_wake_up <-hvc_kick
  kopald-1204    0d.h.  244us : _raw_spin_lock_irqsave <-try_to_wake_up
  kopald-1204    0d.h.  244us : _raw_spin_unlock_irqrestore <-try_to_wake_up

Reported-by: Matteo Croce <mcroce@redhat.com>
Tested-by: Matteo Croce <mcroce@redhat.com>
Tested-by: Jason Gunthorpe <jgg@mellanox.com>
Tested-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit ec97eaad1383 ("tty: hvc: hvc_poll() break hv read loop") causes
the virtio console to hang at times (e.g., if you paste a bunch of
characters to it.

The reason is that get_chars must return 0 before we can be sure the
driver will kick or poll input again, but this change only scheduled a
poll if get_chars had returned a full count. Change this to poll on
any > 0 count.

Reported-by: Matteo Croce <mcroce@redhat.com>
Reported-by: Jason Gunthorpe <jgg@mellanox.com>
Tested-by: Matteo Croce <mcroce@redhat.com>
Tested-by: Jason Gunthorpe <jgg@mellanox.com>
Tested-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull powerpc fixes from Michael Ellerman:

 - An implementation for the newly added hv_ops->flush() for the OPAL
   hvc console driver backends, I forgot to apply this after merging the
   hvc driver changes before the merge window.

 - Enable all PCI bridges at boot on powernv, to avoid races when
   multiple children of a bridge try to enable it simultaneously. This
   is a workaround until the PCI core can be enhanced to fix the races.

 - A fix to query PowerVM for the correct system topology at boot before
   initialising sched domains, seen in some configurations to cause
   broken scheduling etc.

 - A fix for pte_access_permitted() on "nohash" platforms.

 - Two commits to fix SIGBUS when using remap_pfn_range() seen on Power9
   due to a workaround when using the nest MMU (GPUs, accelerators).

 - Another fix to the VFIO code used by KVM, the previous fix had some
   bugs which caused guests to not start in some configurations.

 - A handful of other minor fixes.

Thanks to: Aneesh Kumar K.V, Benjamin Herrenschmidt, Christophe Leroy,
Hari Bathini, Luke Dashjr, Mahesh Salgaonkar, Nicholas Piggin, Paul
Mackerras, Srikar Dronamraju.

* tag 'powerpc-4.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/mce: Fix SLB rebolting during MCE recovery path.
  KVM: PPC: Book3S: Fix guest DMA when guest partially backed by THP pages
  powerpc/mm/radix: Only need the Nest MMU workaround for R -> RW transition
  powerpc/mm/books3s: Add new pte bit to mark pte temporarily invalid.
  powerpc/nohash: fix pte_access_permitted()
  powerpc/topology: Get topology for shared processors at boot
  powerpc64/ftrace: Include ftrace.h needed for enable/disable calls
  powerpc/powernv/pci: Work around races in PCI bridge enabling
  powerpc/fadump: cleanup crash memory ranges support
  powerpc/powernv: provide a console flush operation for opal hvc driver
  powerpc/traps: Avoid rate limit messages from show unhandled signals
  powerpc/64s: Fix PACA_IRQ_HARD_DIS accounting in idle_power4()

Pull core signal handling updates from Eric Biederman:
 "It was observed that a periodic timer in combination with a
  sufficiently expensive fork could prevent fork from every completing.
  This contains the changes to remove the need for that restart.

  This set of changes is split into several parts:

   - The first part makes PIDTYPE_TGID a proper pid type instead
     something only for very special cases. The part starts using
     PIDTYPE_TGID enough so that in __send_signal where signals are
     actually delivered we know if the signal is being sent to a a group
     of processes or just a single process.

   - With that prep work out of the way the logic in fork is modified so
     that fork logically makes signals received while it is running
     appear to be received after the fork completes"

* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (22 commits)
  signal: Don't send signals to tasks that don't exist
  signal: Don't restart fork when signals come in.
  fork: Have new threads join on-going signal group stops
  fork: Skip setting TIF_SIGPENDING in ptrace_init_task
  signal: Add calculate_sigpending()
  fork: Unconditionally exit if a fatal signal is pending
  fork: Move and describe why the code examines PIDNS_ADDING
  signal: Push pid type down into complete_signal.
  signal: Push pid type down into __send_signal
  signal: Push pid type down into send_signal
  signal: Pass pid type into do_send_sig_info
  signal: Pass pid type into send_sigio_to_task & send_sigurg_to_task
  signal: Pass pid type into group_send_sig_info
  signal: Pass pid and pid type into send_sigqueue
  posix-timers: Noralize good_sigevent
  signal: Use PIDTYPE_TGID to clearly store where file signals will be sent
  pid: Implement PIDTYPE_TGID
  pids: Move the pgrp and session pid pointers from task_struct to signal_struct
  kvm: Don't open code task_pid in kvm_vcpu_ioctl
  pids: Compute task_tgid using signal->leader_pid
  ...

Provide the flush hv_op for the opal hvc driver. This will flush the
firmware console buffers without spinning with interrupts disabled.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Pull char/misc driver updates from Greg KH:
 "Here is the bit set of char/misc drivers for 4.19-rc1

  There is a lot here, much more than normal, seems like everyone is
  writing new driver subsystems these days... Anyway, major things here
  are:

   - new FSI driver subsystem, yet-another-powerpc low-level hardware
     bus

   - gnss, finally an in-kernel GPS subsystem to try to tame all of the
     crazy out-of-tree drivers that have been floating around for years,
     combined with some really hacky userspace implementations. This is
     only for GNSS receivers, but you have to start somewhere, and this
     is great to see.

  Other than that, there are new slimbus drivers, new coresight drivers,
  new fpga drivers, and loads of DT bindings for all of these and
  existing drivers.

  All of these have been in linux-next for a while with no reported
  issues"

* tag 'char-misc-4.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (255 commits)
  android: binder: Rate-limit debug and userspace triggered err msgs
  fsi: sbefifo: Bump max command length
  fsi: scom: Fix NULL dereference
  misc: mic: SCIF Fix scif_get_new_port() error handling
  misc: cxl: changed asterisk position
  genwqe: card_base: Use true and false for boolean values
  misc: eeprom: assignment outside the if statement
  uio: potential double frees if __uio_register_device() fails
  eeprom: idt_89hpesx: clean up an error pointer vs NULL inconsistency
  misc: ti-st: Fix memory leak in the error path of probe()
  android: binder: Show extra_buffers_size in trace
  firmware: vpd: Fix section enabled flag on vpd_section_destroy
  platform: goldfish: Retire pdev_bus
  goldfish: Use dedicated macros instead of manual bit shifting
  goldfish: Add missing includes to goldfish.h
  mux: adgs1408: new driver for Analog Devices ADGS1408/1409 mux
  dt-bindings: mux: add adi,adgs1408
  Drivers: hv: vmbus: Cleanup synic memory free path
  Drivers: hv: vmbus: Remove use of slow_virt_to_phys()
  Drivers: hv: vmbus: Reset the channel callback in vmbus_onoffer_rescind()
  ...

Pull tty/serial driver updates from Greg KH:
 "Here is the big tty and serial driver pull request for 4.19-rc1.

  It's not all that big, just a number of small serial driver updates
  and fixes, along with some better vt handling for unicode characters
  for those using braille terminals.

  All of these patches have been in linux-next for a long time with no
  reported issues"

* tag 'tty-4.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (73 commits)
  tty: serial: 8250: Revert NXP SC16C2552 workaround
  serial: 8250_exar: Read INT0 from slave device, too
  tty: rocket: Fix possible buffer overwrite on register_PCI
  serial: 8250_dw: Add ACPI support for uart on Broadcom SoC
  serial: 8250_dw: always set baud rate in dw8250_set_termios
  dt-bindings: serial: Add binding for uartlite
  tty: serial: uartlite: Add support for suspend and resume
  tty: serial: uartlite: Add clock adaptation
  tty: serial: uartlite: Add structure for private data
  serial: sh-sci: Improve support for separate TEI and DRI interrupts
  serial: sh-sci: Remove SCIx_RZ_SCIFA_REGTYPE
  serial: sh-sci: Allow for compressed SCIF address
  serial: sh-sci: Improve interrupts description
  serial: 8250: Use cached port name directly in messages
  serial: 8250_exar: Drop unused variable in pci_xr17v35x_setup()
  vt: drop unused struct vt_struct
  vt: avoid a VLA in the unicode screen scroll function
  vt: add /dev/vcsu* to devices.txt
  vt: coherence validation code for the unicode screen buffer
  vt: selection: take screen contents from uniscr if available
  ...

Pull powerpc updates from Michael Ellerman:
 "Notable changes:

   - A fix for a bug in our page table fragment allocator, where a page
     table page could be freed and reallocated for something else while
     still in use, leading to memory corruption etc. The fix reuses
     pt_mm in struct page (x86 only) for a powerpc only refcount.

   - Fixes to our pkey support. Several are user-visible changes, but
     bring us in to line with x86 behaviour and/or fix outright bugs.
     Thanks to Florian Weimer for reporting many of these.

   - A series to improve the hvc driver & related OPAL console code,
     which have been seen to cause hardlockups at times. The hvc driver
     changes in particular have been in linux-next for ~month.

   - Increase our MAX_PHYSMEM_BITS to 128TB when SPARSEMEM_VMEMMAP=y.

   - Remove Power8 DD1 and Power9 DD1 support, neither chip should be in
     use anywhere other than as a paper weight.

   - An optimised memcmp implementation using Power7-or-later VMX
     instructions

   - Support for barrier_nospec on some NXP CPUs.

   - Support for flushing the count cache on context switch on some IBM
     CPUs (controlled by firmware), as a Spectre v2 mitigation.

   - A series to enhance the information we print on unhandled signals
     to bring it into line with other arches, including showing the
     offending VMA and dumping the instructions around the fault.

  Thanks to: Aaro Koskinen, Akshay Adiga, Alastair D'Silva, Alexey
  Kardashevskiy, Alexey Spirkov, Alistair Popple, Andrew Donnellan,
  Aneesh Kumar K.V, Anju T Sudhakar, Arnd Bergmann, Bartosz Golaszewski,
  Benjamin Herrenschmidt, Bharat Bhushan, Bjoern Noetel, Boqun Feng,
  Breno Leitao, Bryant G. Ly, Camelia Groza, Christophe Leroy, Christoph
  Hellwig, Cyril Bur, Dan Carpenter, Daniel Klamt, Darren Stevens, Dave
  Young, David Gibson, Diana Craciun, Finn Thain, Florian Weimer,
  Frederic Barrat, Gautham R. Shenoy, Geert Uytterhoeven, Geoff Levand,
  Guenter Roeck, Gustavo Romero, Haren Myneni, Hari Bathini, Joel
  Stanley, Jonathan Neuschäfer, Kees Cook, Madhavan Srinivasan, Mahesh
  Salgaonkar, Markus Elfring, Mathieu Malaterre, Mauro S. M. Rodrigues,
  Michael Hanselmann, Michael Neuling, Michael Schmitz, Mukesh Ojha,
  Murilo Opsfelder Araujo, Nicholas Piggin, Parth Y Shah, Paul
  Mackerras, Paul Menzel, Ram Pai, Randy Dunlap, Rashmica Gupta, Reza
  Arbab, Rodrigo R. Galvao, Russell Currey, Sam Bobroff, Scott Wood,
  Shilpasri G Bhat, Simon Guo, Souptick Joarder, Stan Johnson, Thiago
  Jung Bauermann, Tyrel Datwyler, Vaibhav Jain, Vasant Hegde, Venkat
  Rao, zhong jiang"

* tag 'powerpc-4.19-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (234 commits)
  powerpc/mm/book3s/radix: Add mapping statistics
  powerpc/uaccess: Enable get_user(u64, *p) on 32-bit
  powerpc/mm/hash: Remove unnecessary do { } while(0) loop
  powerpc/64s: move machine check SLB flushing to mm/slb.c
  powerpc/powernv/idle: Fix build error
  powerpc/mm/tlbflush: update the mmu_gather page size while iterating address range
  powerpc/mm: remove warning about ‘type’ being set
  powerpc/32: Include setup.h header file to fix warnings
  powerpc: Move `path` variable inside DEBUG_PROM
  powerpc/powermac: Make some functions static
  powerpc/powermac: Remove variable x that's never read
  cxl: remove a dead branch
  powerpc/powermac: Add missing include of header pmac.h
  powerpc/kexec: Use common error handling code in setup_new_fdt()
  powerpc/xmon: Add address lookup for percpu symbols
  powerpc/mm: remove huge_pte_offset_and_shift() prototype
  powerpc/lib: Use patch_site to patch copy_32 functions once cache is enabled
  powerpc/pseries: Fix endianness while restoring of r3 in MCE handler.
  powerpc/fadump: merge adjacent memory ranges to reduce PT_LOAD segements
  powerpc/fadump: handle crash memory ranges array index overflow
  ...

Pull audit patches from Paul Moore:
 "Twelve audit patches for v4.19 and they run the full gamut from fixes
  to features.

  Notable changes include the ability to use the "exe" audit filter
  field in a wider variety of filter types, a fix for our comparison of
  GID/EGID in audit filter rules, better association of related audit
  records (connecting related audit records together into one audit
  event), and a fix for a potential use-after-free in audit_add_watch().

  All the patches pass the audit-testsuite and merge cleanly on your
  current master branch"

* tag 'audit-pr-20180814' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit:
  audit: fix use-after-free in audit_add_watch
  audit: use ktime_get_coarse_real_ts64() for timestamps
  audit: use ktime_get_coarse_ts64() for time access
  audit: simplify audit_enabled check in audit_watch_log_rule_change()
  audit: check audit_enabled in audit_tree_log_remove_rule()
  cred: conditionally declare groups-related functions
  audit: eliminate audit_enabled magic number comparison
  audit: rename FILTER_TYPE to FILTER_EXCLUDE
  audit: Fix extended comparison of GID/EGID
  audit: tie ANOM_ABEND records to syscall
  audit: tie SECCOMP records to syscall
  audit: allow other filter list types for AUDIT_EXE