Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

xen: Code cleanup and small bug fixes

xen/hypervisor.h:
- Remove unused helpers: MULTI_update_va_mapping, is_initial_xendomain,
is_running_on_xen
- Remove unused define CONFIG_X86_PAE
- Remove unused variable xen_start_info: note that it's used inpcifront
which is not built at all
- Remove forward declaration of HYPERVISOR_crash

xen/xen-os.h:
- Remove unused define CONFIG_X86_PAE
- Drop unused helpers: test_and_clear_bit, clear_bit,
force_evtchn_callback
- Implement a generic version (based on ofed/include/linux/bitops.h) of
set_bit and test_bit and prefix them by xen_ to avoid any use by other
code than Xen. Note that It would be worth to investigate a generic
implementation in FreeBSD.
- Replace barrier() by __compiler_membar()
- Replace cpu_relax() by cpu_spinwait(): it's exactly the same as rep;nop
= pause

xen/xen_intr.h:
- Move the prototype of xen_intr_handle_upcall in it: Use by all the
platform

x86/xen/xen_intr.c:
- Use BITSET* for the enabledbits: Avoid to use custom helpers
- test_bit/set_bit has been renamed to xen_test_bit/xen_set_bit
- Don't export the variable xen_intr_pcpu

dev/xen/blkback/blkback.c:
- Fix the string format when XBB_DEBUG is enabled: host_addr is typed
uint64_t

dev/xen/balloon/balloon.c:
- Remove set but not used variable
- Use the correct type for frame_list: xen_pfn_t represents the frame
number on any architecture

dev/xen/control/control.c:
- Return BUS_PROBE_WILDCARD in xs_probe: Returning 0 in a probe callback
means the driver can handle this device. If by any chance xenstore is the
first driver, every new device with the driver is unset will use
xenstore.

dev/xen/grant-table/grant_table.c:
- Remove unused cmpxchg
- Drop unused include opt_pmap.h: Doesn't exist on ARM64 and it doesn't
contain anything required for the code on x86

dev/xen/netfront/netfront.c:
- Use the correct type for rx_pfn_array: xen_pfn_t represents the frame
number on any architecture

dev/xen/netback/netback.c:
- Use the correct type for gmfn: xen_pfn_t represents the frame number on
any architecture

dev/xen/xenstore/xenstore.c:
- Return BUS_PROBE_WILDCARD in xctrl_probe: Returning 0 in a probe callback
means the driver can handle this device. If by any chance xenstore is the
first driver, every new device with the driver is unset will use xenstore.

Note that with the changes, x86/include/xen/xen-os.h doesn't contain anymore
arch-specific code. Although, a new series will add some helpers that differ
between x86 and ARM64, so I've kept the headers for now.

Submitted by: Julien Grall <julien.grall@citrix.com>
Reviewed by: royger
Differential Revision: https://reviews.freebsd.org/D3921
Sponsored by: Citrix Systems R&D

xen-blk{front/back}: remove broken FreeBSD extensions

The FreeBSD extension adds a new request type, called blkif_segment_block
which has a size of 112bytes for both i386 and amd64. This is fine on
amd64, since requests have a size of 112B there also. But this is not true
for i386, where requests have a size of 108B. So on i386 we basically
overrun the ring slot when queuing a request of type blkif_segment_block_t,
which is very bad.

Remove this extension (including a cleanup of the public blkif.h header
file) from blkfront and blkback.

Sponsored by: Citrix Systems R&D
Tested-by: cperciva

Improve the Xen para-virtualized device infrastructure of FreeBSD:

o Add support for backend devices (e.g. blkback)
o Implement extensions to the Xen para-virtualized block API to allow
for larger and more outstanding I/Os.
o Import a completely rewritten block back driver with support for fronting
I/O to both raw devices and files.
o General cleanup and documentation of the XenBus and XenStore support code.
o Robustness and performance updates for the block front driver.
o Fixes to the netfront driver.

Sponsored by: Spectra Logic Corporation

sys/xen/xenbus/init.txt:
Deleted: This file explains the Linux method for XenBus device
enumeration and thus does not apply to FreeBSD's NewBus approach.

sys/xen/xenbus/xenbus_probe_backend.c:
Deleted: Linux version of backend XenBus service routines. It
was never ported to FreeBSD. See xenbusb.c, xenbusb_if.m,
xenbusb_front.c xenbusb_back.c for details of FreeBSD's XenBus
support.

sys/xen/xenbus/xenbusvar.h:
sys/xen/xenbus/xenbus_xs.c:
sys/xen/xenbus/xenbus_comms.c:
sys/xen/xenbus/xenbus_comms.h:
sys/xen/xenstore/xenstorevar.h:
sys/xen/xenstore/xenstore.c:
Split XenStore into its own tree. XenBus is a software layer built
on top of XenStore. The old arrangement and the naming of some
structures and functions blurred these lines making it difficult to
discern what services are provided by which layer and at what times
these services are available (e.g. during system startup and shutdown).

sys/xen/xenbus/xenbus_client.c:
sys/xen/xenbus/xenbus.c:
sys/xen/xenbus/xenbus_probe.c:
sys/xen/xenbus/xenbusb.c:
sys/xen/xenbus/xenbusb.h:
Split up XenBus code into methods available for use by client
drivers (xenbus.c) and code used by the XenBus "bus code" to
enumerate, attach, detach, and service bus drivers.

sys/xen/reboot.c:
sys/dev/xen/control/control.c:
Add a XenBus front driver for handling shutdown, reboot, suspend, and
resume events published in the XenStore. Move all PV suspend/reboot
support from reboot.c into this driver.

sys/xen/blkif.h:
New file from Xen vendor with macros and structures used by
a block back driver to service requests from a VM running a
different ABI (e.g. amd64 back with i386 front).

sys/conf/files:
Adjust kernel build spec for new XenBus/XenStore layout and added
Xen functionality.

sys/dev/xen/balloon/balloon.c:
sys/dev/xen/netfront/netfront.c:
sys/dev/xen/blkfront/blkfront.c:
sys/xen/xenbus/...
sys/xen/xenstore/...
o Rename XenStore APIs and structures from xenbus_* to xs_*.
o Adjust to use of M_XENBUS and M_XENSTORE malloc types for allocation
of objects returned by these APIs.
o Adjust for changes in the bus interface for Xen drivers.

sys/xen/xenbus/...
sys/xen/xenstore/...
Add Doxygen comments for these interfaces and the code that
implements them.

sys/dev/xen/blkback/blkback.c:
o Rewrite the Block Back driver to attach properly via newbus,
operate correctly in both PV and HVM mode regardless of domain
(e.g. can be in a DOM other than 0), and to deal with the latest
metadata available in XenStore for block devices.

o Allow users to specify a file as a backend to blkback, in addition
to character devices. Use the namei lookup of the backend path
to automatically configure, based on file type, the appropriate
backend method.

The current implementation is limited to a single outstanding I/O
at a time to file backed storage.

sys/dev/xen/blkback/blkback.c:
sys/xen/interface/io/blkif.h:
sys/xen/blkif.h:
sys/dev/xen/blkfront/blkfront.c:
sys/dev/xen/blkfront/block.h:
Extend the Xen blkif API: Negotiable request size and number of
requests.

This change extends the information recorded in the XenStore
allowing block front/back devices to negotiate for optimal I/O
parameters. This has been achieved without sacrificing backward
compatibility with drivers that are unaware of these protocol
enhancements. The extensions center around the connection protocol
which now includes these additions:

o The back-end device publishes its maximum supported values for,
request I/O size, the number of page segments that can be
associated with a request, the maximum number of requests that
can be concurrently active, and the maximum number of pages that
can be in the shared request ring. These values are published
before the back-end enters the XenbusStateInitWait state.

o The front-end waits for the back-end to enter either the InitWait
or Initialize state. At this point, the front end limits it's
own capabilities to the lesser of the values it finds published
by the backend, it's own maximums, or, should any back-end data
be missing in the store, the values supported by the original
protocol. It then initializes it's internal data structures
including allocation of the shared ring, publishes its maximum
capabilities to the XenStore and transitions to the Initialized
state.

o The back-end waits for the front-end to enter the Initalized
state. At this point, the back end limits it's own capabilities
to the lesser of the values it finds published by the frontend,
it's own maximums, or, should any front-end data be missing in
the store, the values supported by the original protocol. It
then initializes it's internal data structures, attaches to the
shared ring and transitions to the Connected state.

o The front-end waits for the back-end to enter the Connnected
state, transitions itself to the connected state, and can
commence I/O.

Although an updated front-end driver must be aware of the back-end's
InitWait state, the back-end has been coded such that it can
tolerate a front-end that skips this step and transitions directly
to the Initialized state without waiting for the back-end.

sys/xen/interface/io/blkif.h:
o Increase BLKIF_MAX_SEGMENTS_PER_REQUEST to 255. This is
the maximum number possible without changing the blkif
request header structure (nr_segs is a uint8_t).

o Add two new constants:
BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK, and
BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK. These respectively
indicate the number of segments that can fit in the first
ring-buffer entry of a request, and for each subsequent
(sg element only) ring-buffer entry associated with the
"header" ring-buffer entry of the request.

o Add the blkif_request_segment_t typedef for segment
elements.

o Add the BLKRING_GET_SG_REQUEST() macro which wraps the
RING_GET_REQUEST() macro and returns a properly cast
pointer to an array of blkif_request_segment_ts.

o Add the BLKIF_SEGS_TO_BLOCKS() macro which calculates the
number of ring entries that will be consumed by a blkif
request with the given number of segments.

sys/xen/blkif.h:
o Update for changes in interface/io/blkif.h macros.

o Update the BLKIF_MAX_RING_REQUESTS() macro to take the
ring size as an argument to allow this calculation on
multi-page rings.

o Add a companion macro to BLKIF_MAX_RING_REQUESTS(),
BLKIF_RING_PAGES(). This macro determines the number of
ring pages required in order to support a ring with the
supplied number of request blocks.

sys/dev/xen/blkback/blkback.c:
sys/dev/xen/blkfront/blkfront.c:
sys/dev/xen/blkfront/block.h:
o Negotiate with the other-end with the following limits:
Reqeust Size: MAXPHYS
Max Segments: (MAXPHYS/PAGE_SIZE) + 1
Max Requests: 256
Max Ring Pages: Sufficient to support Max Requests with
Max Segments.

o Dynamically allocate request pools and segemnts-per-request.

o Update ring allocation/attachment code to support a
multi-page shared ring.

o Update routines that access the shared ring to handle
multi-block requests.

sys/dev/xen/blkfront/blkfront.c:
o Track blkfront allocations in a blkfront driver specific
malloc pool.

o Strip out XenStore transaction retry logic in the
connection code. Transactions only need to be used when
the update to multiple XenStore nodes must be atomic.
That is not the case here.

o Fully disable blkif_resume() until it can be fixed
properly (it didn't work before this change).

o Destroy bus-dma objects during device instance tear-down.

o Properly handle backend devices with powef-of-2 sector
sizes larger than 512b.

sys/dev/xen/blkback/blkback.c:
Advertise support for and implement the BLKIF_OP_WRITE_BARRIER
and BLKIF_OP_FLUSH_DISKCACHE blkif opcodes using BIO_FLUSH and
the BIO_ORDERED attribute of bios.

sys/dev/xen/blkfront/blkfront.c:
sys/dev/xen/blkfront/block.h:
Fix various bugs in blkfront.

o gnttab_alloc_grant_references() returns 0 for success and
non-zero for failure. The check for < 0 is a leftover
Linuxism.

o When we negotiate with blkback and have to reduce some of our
capabilities, print out the original and reduced capability before
changing the local capability. So the user now gets the correct
information.

o Fix blkif_restart_queue_callback() formatting. Make sure we hold
the mutex in that function before calling xb_startio().

o Fix a couple of KASSERT()s.

o Fix a check in the xb_remove_* macro to be a little more specific.

sys/xen/gnttab.h:
sys/xen/gnttab.c:
Define GNTTAB_LIST_END publicly as GRANT_REF_INVALID.

sys/dev/xen/netfront/netfront.c:
Use GRANT_REF_INVALID instead of driver private definitions of the
same constant.

sys/xen/gnttab.h:
sys/xen/gnttab.c:
Add the gnttab_end_foreign_access_references() API.

This API allows a client to batch the release of an array of grant
references, instead of coding a private for loop. The implementation
takes advantage of this batching to reduce lock overhead to one
acquisition and release per-batch instead of per-freed grant reference.

While here, reduce the duration the gnttab_list_lock is held during
gnttab_free_grant_references() operations. The search to find the
tail of the incoming free list does not rely on global state and so
can be performed without holding the lock.

sys/dev/xen/xenpci/evtchn.c:
sys/dev/xen/evtchn/evtchn.c:
sys/xen/xen_intr.h:
o Implement the bind_interdomain_evtchn_to_irqhandler API for HVM mode.
This allows an HVM domain to serve back end devices to other domains.
This API is already implemented for PV mode.

o Synchronize the API between HVM and PV.

sys/dev/xen/xenpci/xenpci.c:
o Scan the full region of CPUID space in which the Xen VMM interface
may be implemented. On systems using SuSE as a Dom0 where the
Viridian API is also exported, the VMM interface is above the region
we used to search.

o Pass through bus_alloc_resource() calls so that XenBus drivers
attaching on an HVM system can allocate unused physical address
space from the nexus. The block back driver makes use of this
facility.

sys/i386/xen/xen_machdep.c:
Use the correct type for accessing the statically mapped xenstore
metadata.

sys/xen/interface/hvm/params.h:
sys/xen/xenstore/xenstore.c:
Move hvm_get_parameter() to the correct global header file instead
of as a private method to the XenStore.

sys/xen/interface/io/protocols.h:
Sync with vendor.

sys/xeninterface/io/ring.h:
Add macro for calculating the number of ring pages needed for an N
deep ring.

To avoid duplication within the macros, create and use the new
__RING_HEADER_SIZE() macro. This macro calculates the size of the
ring book keeping struct (producer/consumer indexes, etc.) that
resides at the head of the ring.

Add the __RING_PAGES() macro which calculates the number of shared
ring pages required to support a ring with the given number of
requests.

These APIs are used to support the multi-page ring version of the
Xen block API.

sys/xeninterface/io/xenbus.h:
Add Comments.

sys/xen/xenbus/...
o Refactor the FreeBSD XenBus support code to allow for both front and
backend device attachments.

o Make use of new config_intr_hook capabilities to allow front and back
devices to be probed/attached in parallel.

o Fix bugs in probe/attach state machine that could cause the system to
hang when confronted with a failure either in the local domain or in
a remote domain to which one of our driver instances is attaching.

o Publish all required state to the XenStore on device detach and
failure. The majority of the missing functionality was for serving
as a back end since the typical "hot-plug" scripts in Dom0 don't
handle the case of cleaning up for a "service domain" that is not
itself.

o Add dynamic sysctl nodes exposing the generic ivars of
XenBus devices.

o Add doxygen style comments to the majority of the code.

o Cleanup types, formatting, etc.

sys/xen/xenbus/xenbusb.c:
Common code used by both front and back XenBus busses.

sys/xen/xenbus/xenbusb_if.m:
Method definitions for a XenBus bus.

sys/xen/xenbus/xenbusb_front.c:
sys/xen/xenbus/xenbusb_back.c:
XenBus bus specialization for front and back devices.

MFC after: 1 month