* Generalize GPIO handling.
* Add libs to configure gpio's clocks and pads
* Add Interrupt handling.
* Introduce mmio.h and log.h
Change-Id: I928e4c807d15031de2eede4b3ecff62df795f8ac
* let busy loops timeout.
* Start using interrupt handlers.
* Allocate the ramdisk only when used.
Change-Id: Ie08d66eefef3c8cd3ee16c04f74a9a50cc12b021
Small GPIO driver that exports a few pins using a virtual file
system. Currently the two user leds and the user button are exported.
Change-Id: I001d017ae27cd17b635587873f7da981054da459
Due to the ABI we are using we have to use the earm architecture
moniker for the build system to behave correctly. This involves
then some headers to move around.
There is also a few related Makefile updates as well as minor
source code corrections.
* Updating common/lib
* Updating lib/csu
* Updating lib/libc
* Updating libexec/ld.elf_so
* Corrected test on __minix in featuretest to actually follow the
meaning of the comment.
* Cleaned up _REENTRANT-related defintions.
* Disabled -D_REENTRANT for libfetch
* Removing some unneeded __NBSD_LIBC defines and tests
Change-Id: Ic1394baef74d11b9f86b312f5ff4bbc3cbf72ce2
Replace proto.sh by the c processor to generate proto.gen in order
for us to have a more flexible way of selecting the files we want
in the ramdisk.
Change-Id: Id82b9f1b73b498c4d885bb3156fcefaeb9d157e0
Also fix a potential issue where host tools would be compiled
dynamically under MINIX.
This also updates proto.common.dynamic to use the new placement
of the dynamic libraries (/usr/lib)
upgrade to NetBSD CVS release from 2012/10/17 12:00:00 UTC
Makefiles updates to imporve portability
Made sure to be consistent in the usage of braces/parenthesis at
least on a per file basis. For variables, it is recommended to
continue to use braces.
The tested targets are the followgin ones:
* tools
* distribution
* sets
* release
The remaining NetBSD targets have not been disabled nor tested
*at all*. Try them at your own risk, they may reboot the earth.
For all compliant Makefiles, objects and generated files are put in
MAKEOBJDIR, which means you can now keep objects between two branch
switching. Same for DESTDIR, please refer to build.sh options.
Regarding new or modifications of Makefiles a few things:
* Read share/mk/bsd.README
* If you add a subdirectory, add a Makefile in it, and have it called
by the parent through the SUBDIR variable.
* Do not add arbitrary inclusion which crosses to another branch of
the hierarchy; If you can't do without it, put a comment on why.
If possible, do not use inclusion at all.
* Use as much as possible the infrastructure, it is here to make
life easier, do not fight it.
Sets and package are now used to track files.
We have one set called "minix", composed of one package called "minix-sys"
.Split TTY in order to support both x86 and ARM.
.Add support for the TI 16750 UARTs on OMAP35x.
.Various other improvements:
.Kernel messages are printed using generic terminal write
functions. That is, they are no longer directly displayed
on the console.
.The console can now be displayed on any terminal. This
is configured by the "console={tty00,tty01,ttyc2,ttyc3,ttyc4}"
boot variable -- basically any valid /dev/tty* terminal.
.Cutify kernel messages with colors. Configured by
"kernelclr={1,2,3,4,5,6,7}" boot variable.
* Add dummy driver to allow independent testing of mmcblk.
* Always build the mmc driver to prevent breakage.
* Allow to specify the mmc driver to be used at load time.
Change-Id: I4e14b912fb8f3612e252864b53733968b23ac023
complete munmap implementation; single-page references made
a general munmap() implementation possible to write cleanly.
. memory: let the MIOCRAMSIZE ioctl set the imgrd device
size (but only to 0)
. let the ramdisk command set sizes to 0
. use this command to set /dev/imgrd to 0 after mounting /usr
in /etc/rc, so the boot time ramdisk is freed (about 4MB
currently)
By decoupling synchronous drivers from VFS, we are a big step closer to
supporting driver crashes under all circumstances. That is, VFS can't
become stuck on IPC with a synchronous driver (e.g., INET) and can
recover from crashing block drivers during open/close/ioctl or during
communication with an FS.
In order to maintain serialized communication with a synchronous driver,
the communication is wrapped by a mutex on a per driver basis (not major
numbers as there can be multiple majors with identical endpoints). Majors
that share a driver endpoint point to a single mutex object.
In order to support crashes from block drivers, the file reopen tactic
had to be changed; first reopen files associated with the crashed
driver, then send the new driver endpoint to FSes. This solves a
deadlock between the FS and the block driver;
- VFS would send REQ_NEW_DRIVER to an FS, but he FS only receives it
after retrying the current request to the newly started driver.
- The block driver would refuse the retried request until all files
had been reopened.
- VFS would reopen files only after getting a reply from the initial
REQ_NEW_DRIVER.
When a character special driver crashes, all associated files have to
be marked invalid and closed (or reopened if flagged as such). However,
they can only be closed if a thread holds exclusive access to it. To
obtain exclusive access, the worker thread (which handles the new driver
endpoint event from DS) schedules a new job to garbage collect invalid
files. This way, we can signal the worker thread that was talking to the
crashed driver and will release exclusive access to a file associated
with the crashed driver and prevent the garbage collecting worker thread
from dead locking on that file.
Also, when a character special driver crashes, RS will unmap the driver
and remap it upon restart. During unmapping, associated files are marked
invalid instead of waiting for an endpoint up event from DS, as that
event might come later than new read/write/select requests and thus
cause confusion in the freshly started driver.
When locking a filp, the usage counters are no longer checked. The usage
counter can legally go down to zero during filp invalidation while there
are locks pending.
DS events are handled by a separate worker thread instead of the main
thread as reopening files could lead to another crash and a stuck thread.
An additional worker thread is then necessary to unlock it.
Finally, with everything asynchronous a race condition in do_select
surfaced. A select entry was only marked in use after succesfully sending
initial select requests to drivers and having to wait. When multiple
select() calls were handled there was opportunity that these entries
were overwritten. This had as effect that some select results were
ignored (and select() remained blocking instead if returning) or do_select
tried to access filps that were not present (because thrown away by
secondary select()). This bug manifested itself with sendrecs, but was
very hard to reproduce. However, it became awfully easy to trigger with
asynsends only.
. map all objects named usermapped_*.o with globally visible
pages; usermapped_glo_*.o with the VM 'global' bit on, i.e.
permanently in tlb (very scarce resource!)
. added kinfo, machine, kmessages and loadinfo for a start
. modified log, tty to make use of the shared messages struct
. some strncpy/strcpy to strlcpy conversions
. new <minix/param.h> to avoid including other minix headers
that have colliding definitions with library and commands code,
causing parse warnings
. removed some dead code / assignments
This commit removes all traces of Minix segments (the text/data/stack
memory map abstraction in the kernel) and significance of Intel segments
(hardware segments like CS, DS that add offsets to all addressing before
page table translation). This ultimately simplifies the memory layout
and addressing and makes the same layout possible on non-Intel
architectures.
There are only two types of addresses in the world now: virtual
and physical; even the kernel and processes have the same virtual
address space. Kernel and user processes can be distinguished at a
glance as processes won't use 0xF0000000 and above.
No static pre-allocated memory sizes exist any more.
Changes to booting:
. The pre_init.c leaves the kernel and modules exactly as
they were left by the bootloader in physical memory
. The kernel starts running using physical addressing,
loaded at a fixed location given in its linker script by the
bootloader. All code and data in this phase are linked to
this fixed low location.
. It makes a bootstrap pagetable to map itself to a
fixed high location (also in linker script) and jumps to
the high address. All code and data then use this high addressing.
. All code/data symbols linked at the low addresses is prefixed by
an objcopy step with __k_unpaged_*, so that that code cannot
reference highly-linked symbols (which aren't valid yet) or vice
versa (symbols that aren't valid any more).
. The two addressing modes are separated in the linker script by
collecting the unpaged_*.o objects and linking them with low
addresses, and linking the rest high. Some objects are linked
twice, once low and once high.
. The bootstrap phase passes a lot of information (e.g. free memory
list, physical location of the modules, etc.) using the kinfo
struct.
. After this bootstrap the low-linked part is freed.
. The kernel maps in VM into the bootstrap page table so that VM can
begin executing. Its first job is to make page tables for all other
boot processes. So VM runs before RS, and RS gets a fully dynamic,
VM-managed address space. VM gets its privilege info from RS as usual
but that happens after RS starts running.
. Both the kernel loading VM and VM organizing boot processes happen
using the libexec logic. This removes the last reason for VM to
still know much about exec() and vm/exec.c is gone.
Further Implementation:
. All segments are based at 0 and have a 4 GB limit.
. The kernel is mapped in at the top of the virtual address
space so as not to constrain the user processes.
. Processes do not use segments from the LDT at all; there are
no segments in the LDT any more, so no LLDT is needed.
. The Minix segments T/D/S are gone and so none of the
user-space or in-kernel copy functions use them. The copy
functions use a process endpoint of NONE to realize it's
a physical address, virtual otherwise.
. The umap call only makes sense to translate a virtual address
to a physical address now.
. Segments-related calls like newmap and alloc_segments are gone.
. All segments-related translation in VM is gone (vir2map etc).
. Initialization in VM is simpler as no moving around is necessary.
. VM and all other boot processes can be linked wherever they wish
and will be mapped in at the right location by the kernel and VM
respectively.
Other changes:
. The multiboot code is less special: it does not use mb_print
for its diagnostics any more but uses printf() as normal, saving
the output into the diagnostics buffer, only printing to the
screen using the direct print functions if a panic() occurs.
. The multiboot code uses the flexible 'free memory map list'
style to receive the list of free memory if available.
. The kernel determines the memory layout of the processes to
a degree: it tells VM where the kernel starts and ends and
where the kernel wants the top of the process to be. VM then
uses this entire range, i.e. the stack is right at the top,
and mmap()ped bits of memory are placed below that downwards,
and the break grows upwards.
Other Consequences:
. Every process gets its own page table as address spaces
can't be separated any more by segments.
. As all segments are 0-based, there is no distinction between
virtual and linear addresses, nor between userspace and
kernel addresses.
. Less work is done when context switching, leading to a net
performance increase. (8% faster on my machine for 'make servers'.)
. The layout and configuration of the GDT makes sysenter and syscall
possible.
. Some Makefile fixes to automatically differentiate between a normal
compilation and cross-compilation. Also, build compressed images.
. Harmonize ramdisk rc scripts for normal use case and ext2 ramdisk.
. ext2_ramdisk filesystem prototype fixes.
. all invocations were S or D, so can safely be dropped
to prepare for the segmentless world
. still assign D to the SCP_SEG field in the message
to make previous kernels usable
WARNING: this will break existing dynamically linked binaries if they
exist. If you have any:
. re-build world statically first if necessary
. remove libraries from /lib and /usr/lib
. then build world
This change:
. avoids possible future dismay when interfacing other
systems' binaries; done until they are abi-compatible
Thanks to Antoine Leca for pointing this out.
. readbios call is now a physical copy with range check in
the kernel call instead of BIOS_SEG+umap_bios
. requires all access to physical memory in bios range to go
through sys_readbios
. drivers/dpeth: wasn't using it
. adjusted printer
. make ramdisk buildable without ../etc having pwd.db
. add cat to release bootstrap cmds
. support running dynamically linked executables for
release bootstrap cmds
. import netbsd chroot to help
See UPDATING about upgrading clang for dynamic linking.
. allow executables on ramdisk to be dynamically linked; this means
putting a few required shared libraries and ld.elf_so on the ramdisk.
. this makes the ramdisk (usage) smaller when they are dynamic, but
bigger when they're not.
. also we can safely ditch newroot and call mount directly as that is
all newroot does.
. create proto.common to share a bunch of entries between
small/nonsmall cases
building defaults to off until clang is updated.
current clang does not handle -shared, necessary to change the ld
invocation to build shared libraries properly. a new clang should be
installed and MKPIC defaults to no unless the newer clang is detected.
changes:
. mainly small imports of a Makefile or two and small fixes
(turning things back on that were turned off in Makefiles)
. e.g.: dynamic librefuse now depends on dynamic
libpuffs, so libpuffs has to be built dynamically too
and a make dependency barrier is needed in lib/Makefile
. all library objects now have a PIC (for .so) and non-PIC
version, so everything is built twice.
. generate PIC versions of the compat (un-RENAMEd) jump files,
include function type annotation in generated assembly
. build progs with -static by default for now
. also build ld.elf_so
. also import NetBSD ldd
TTY has no way of keeping track of multiple readers for a tty minor
device. Instead, it stores a read request for the last reader only.
Consequently, the first ("overwritten") reader gets stuck on a read
request that's never going to be finished. Also, the overwriting
causes a grant mismatch in VFS when TTY returns a reply for the
second reader.
This patch is a work around for the actual problem (i.e., keeping track
of multiple readers). It checks whether there is a read operation in
progress and returns an error if it is --preventing that reader from
getting overwritten and stuck. It fixes a bug triggered by executing
'top | more' and pressing the space bar for a while (easily reproducable
in a VM, not on hardware).
- add files needed for acpi, ahci, fbd, vfs to libminc
- remove "-lc" from their respective makefiles
- remove setenv from libminc (requires initialization)
- remove PCI tables where system.conf suffices
- remove drivers' ability to mess up NIC order
- fix dp8390 PCI enumeration
- convert ti1225 to instance model
- add system.conf entry for ti1225
- if an operation (R, W, IOCTL) is non blocking, a flag is set
and sent to the device.
- nothing changes for sync devices
- asyn devices should reply asap if an operation is non-blocking.
We must trust the devices, but we had to trust them anyway to
reply to CANCEL correctly
- we safe sending CANCEL commands to asyn devices. This greatly
simplifies the protocol. Asynchronous devices can always reply
when a reply is ready and do not need to deal with other
situations
- currently, none of our drivers use the flags since they drive
virtual devices which do not block
There is important information about booting non-ack images in
docs/UPDATING. ack/aout-format images can't be built any more, and
booting clang/ELF-format ones is a little different. Updating to the
new boot monitor is recommended.
Changes in this commit:
. drop boot monitor -> allowing dropping ack support
. facility to copy ELF boot files to /boot so that old boot monitor
can still boot fairly easily, see UPDATING
. no more ack-format libraries -> single-case libraries
. some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases
. drop several ack toolchain commands, but not all support
commands (e.g. aal is gone but acksize is not yet).
. a few libc files moved to netbsd libc dir
. new /bin/date as minix date used code in libc/
. test compile fix
. harmonize includes
. /usr/lib is no longer special: without ack, /usr/lib plays no
kind of special bootstrapping role any more and bootstrapping
is done exclusively through packages, so releases depend even
less on the state of the machine making them now.
. rename nbsd_lib* to lib*
. reduce mtree
Instead of using rootdev= or ramimagedev= in the boot monitor
which are changed to numbers and cannot be used with other
loaders, rootdevname= or ramimagename= are (MINIX-style)
device names always stored as strings.
Patch by Antoine Leca.
- change AcpiOsRemoveInterruptHandler() to print a warning
instead of panic.
- we do the same in AcpiOsInstallInterruptHandler().
Signed-off-by: Tomas Hruby <thruby@few.vu.nl>
. pre-cleanflag ("old") mkfs generates without CLEAN flag,
causing boot not working because imgrd disappears after 1st
close
. fixed sanity check for this situation
. disable imgrd disappearing in memory driver so
readonly mount succeeds in case it happens anyway
. also implement now-possible fsck -p option
. allows unconditional fsck -p invocation at startup,
only checking each filesystem if not marked clean
. mounting unclean is allowed but is forced readonly
. updating the superblock while mounted is now not
allowed by mfs - must be done (e.g. by fsck.mfs)
on an unmounted fs
. clean flag is unset by mfs on mounting, and set by
mfs on clean unmounting (if clean flag was set at
mount time)
Signed-off-by: Ben Gras <ben@minix3.org>
- if no IRQ table is found, we report that ACPI cannot map IRQ
correctly
- fixes mapping of IRQs in KVM because in this case we just fall
through and use the IRQ configured by BIOS. PCI still reports
that it failed to use ACPI. It is a hint if things go wrong.
This driver can be loaded as an overlay on top of a real block
device, and can then be used to generate block-level failures for
certain transfer requests. Specifically, a rule-based system allows
the user to introduce (overt and silent) data corruption and errors.
It exposes itself through /dev/fbd, and a file system can be mounted
on top of it. The new fbdctl(8) tool can be used to control the
driver; see ``man fbdctl'' for details. It also comes with a test
set, located in test/fbdtest.
This removes a race condition when the block driver performs a
complete restart after a crash (the new default). If any user of
the driver finds out its new endpoint and sends a request to the
new driver instance before this instance has had the chance to
initialize, then its initialization would clear all IPC state and
thereby erroneously cancel the incoming request. Clearing IPC
state is only desired upon a stateful restart (where the driver's
endpoint is retained). This information is now passed to and used
by libblockdriver accordingly.
This stops the printer driver from hanging the entire system when
/dev/lp is opened on systems that do not have a parallel port. With
this change, the printer driver shuts down immediately after loading
on such systems.
Each block driver now gets to specify whether it is a disk block
driver, which implies it wants the library to handle getting and
setting partitions for it.
This patch separates the character and block driver communication
protocols. The old character protocol remains the same, but a new
block protocol is introduced. The libdriver library is replaced by
two new libraries: libchardriver and libblockdriver. Their exposed
API, and drivers that use them, have been updated accordingly.
Together, libbdev and libblockdriver now completely abstract away
the message format used by the block protocol. As the memory driver
is both a character and a block device driver, it now implements its
own message loop.
The most important semantic change made to the block protocol is that
it is no longer possible to return both partial results and an error
for a single transfer. This simplifies the interaction between the
caller and the driver, as the I/O vector no longer needs to be copied
back. Also, drivers are now no longer supposed to decide based on the
layout of the I/O vector when a transfer should be cut short. Put
simply, transfers are now supposed to either succeed completely, or
result in an error.
After this patch, the state of the various pieces is as follows:
- block protocol: stable
- libbdev API: stable for synchronous communication
- libblockdriver API: needs slight revision (the drvlib/partition API
in particular; the threading API will also change shortly)
- character protocol: needs cleanup
- libchardriver API: needs cleanup accordingly
- driver restarts: largely unsupported until endpoint changes are
reintroduced
As a side effect, this patch eliminates several bugs, hacks, and gcc
-Wall and -W warnings all over the place. It probably introduces a
few new ones, too.
Update warning: this patch changes the protocol between MFS and disk
drivers, so in order to use old/new images, the MFS from the ramdisk
must be used to mount all file systems.
. always compile acpi, with clang, so never have
build/clean inconsistencies; can be enabled (i.e. run
at boot time) by setting acpi variable in the boot monitor
. always strip binaries with the right strip cmd, so never
have ack/elf strip inconsistencies
. rc script and service know to look in /usr/pkg/.. for
extra binaries and conf files
. service split into parsing config and doing RS request
so that a new utility (printconfig) can just print the
config in machine-parseable format for netconf integration
. converted all base system eth drivers/netconf
While no problems have been observed in practice yet, modern compilers
may reorder memory access operations, and that could lead to problems
with memory-mapped I/O typically done by drivers. This patch prevents
any potentially problematic reordering by the compiler in the ATL2
driver.
In addition, this patch removes a number of gcc/clang warnings.
While no problems have been observed in practice yet, modern compilers
may reorder memory access operations, and that could lead to problems
with memory-mapped I/O typically done by drivers. This patch prevents
any potentially problematic reordering by the compiler in the AHCI
driver.
This patch adds support for executing multiple concurrent requests on
different devices on the same AHCI controller. The libdriver library
has been extended to include a generic multithreading interface, and
the AHCI driver has been extended to make use of this interface.
The original version of this code has been written by Arne Welzel.
Improves cache locality by grouping together dependency generation
with building for each program instead of doing a whole-tree dep
generation phase followed by a whole-tree build phase
. it's a good extra interface to have but doesn't
meet standardised functionality
. applications (in pkgsrc) find it and expect
full functionality the minix mmap doesn't offter
. on the whole probably better to hide these functions
(mmap and friends) until they are grown up; the base system
can use the new minix_* names
- the pointers must be flagged as volatile because otherwise they
might be "optimized" by a compiler. It is a common good
practice to access the registers this way, the keyword is in C
for a reason.
- for instance, in eeprom_eerd() when polling a register the
compiler, under certain conditions, may decide upon the first
read and if it does not break the loop it assumes that the
value is not going to change and thus stays in an infinite
loop.
3 sets of libraries are built now:
. ack: all libraries that ack can compile (/usr/lib/i386/)
. clang+elf: all libraries with minix headers (/usr/lib/)
. clang+elf: all libraries with netbsd headers (/usr/netbsd/)
Once everything can be compiled with netbsd libraries and headers, the
/usr/netbsd hierarchy will be obsolete and its libraries compiled with
netbsd headers will be installed in /usr/lib, and its headers
in /usr/include. (i.e. minix libc and current minix headers set
will be gone.)
To use the NetBSD libc system (libraries + headers) before
it is the default libc, see:
http://wiki.minix3.org/en/DevelopersGuide/UsingNetBSDCode
This wiki page also documents the maintenance of the patch
files of minix-specific changes to imported NetBSD code.
Changes in this commit:
. libsys: Add NBSD compilation and create a safe NBSD-based libc.
. Port rest of libraries (except libddekit) to new header system.
. Enable compilation of libddekit with new headers.
. Enable kernel compilation with new headers.
. Enable drivers compilation with new headers.
. Port legacy commands to new headers and libc.
. Port servers to new headers.
. Add <sys/sigcontext.h> in compat library.
. Remove dependency file in tree.
. Enable compilation of common/lib/libc/atomic in libsys
. Do not generate RCSID strings in libc.
. Temporarily disable zoneinfo as they are incompatible with NetBSD format
. obj-nbsd for .gitignore
. Procfs: use only integer arithmetic. (Antoine Leca)
. Increase ramdisk size to create NBSD-based images.
. Remove INCSYMLINKS handling hack.
. Add nbsd_include/sys/exec_elf.h
. Enable ELF compilation with NBSD libc.
. Add 'make nbsdsrc' in tools to download reference NetBSD sources.
. Automate minix-port.patch creation.
. Avoid using fstavfs() as it is *extremely* slow and unneeded.
. Set err() as PRIVATE to avoid name clash with libc.
. [NBSD] servers/vm: remove compilation warnings.
. u32 is not a long in NBSD headers.
. UPDATING info on netbsd hierarchy
. commands fixes for netbsd libc
sys_umap now supports only:
- looking up the physical address of a virtual address in the address space
of the caller;
- looking up the physical address of a grant for which the caller is the
grantee.
This is enough for nearly all umap users. The new sys_umap_remote supports
lookups in arbitrary address spaces and grants for arbitrary grantees.
- when ACPI does not find mappings for pci brdiges, do no panic,
only report a warning and continue to a fallback which uses
only the root bus IRQ routing table. Fail only if that is not
present.
Before safecopies, the IO_ENDPT and DL_ENDPT message fields were needed
to know which actual process to copy data from/to, as that process may
not always be the caller. Now that we have full safecopy support, these
fields have become useless for that purpose: the owner of the grant is
*always* the caller. Allowing the caller to supply another endpoint is
in fact dangerous, because the callee may then end up using a grant
from a third party. One could call this a variant of the confused
deputy problem.
From now on, safecopy calls should always use the caller's endpoint as
grant owner. This fully obsoletes the DL_ENDPT field in the
inet/ethernet protocol. IO_ENDPT has other uses besides identifying the
grant owner though. This patch renames IO_ENDPT to USER_ENDPT, not only
because that is a more fitting name (it should never be used for I/O
after all), but also in order to intentionally break any old system
source code outside the base system. If this patch breaks your code,
fixing it is fairly simple:
- DL_ENDPT should be replaced with m_source;
- IO_ENDPT should be replaced with m_source when used for safecopies;
- IO_ENDPT should be replaced with USER_ENDPT for any other use, e.g.
when setting REP_ENDPT, matching requests in CANCEL calls, getting
DEV_SELECT flags, and retrieving of the real user process's endpoint
in DEV_OPEN.
The changes in this patch are binary backward compatible.
M include/Makefile
A include/minix/input.h
M include/minix/com.h
M drivers/tty/keyboard.c
M drivers/tty/tty.c
M drivers/tty/tty.h
M include/minix/syslib.h
M lib/libsys/Makefile
A lib/libsys/input.c
- every pci device which implements _PRT acpi method is considered to
be a pci-to-pci bridge
- acpi driver constructs a hierarchy of pci-to-pci bridges
- when pci driver identifies a pci-to-pci bridge it tells acpi driver
what is the primary and the secondary bus for this device
- when pci requests IRQ routing information from acpi, it passes the
bus number too to be able to identify the device accurately
- kernel turns on IO APICs if no_apic is _not_ set or is equal 0
- pci driver must use the acpi driver to setup IRQ routing otherwise
the system cannot work correctly except systems like KVM that use
only legacy (E)ISA IRQs 0-15
- PCI must query ACPI, if (IO)APIC is in use, for the routing
information and change the ILR (interrupt line register) of each
device accordingly so drivers use the right IRQ.
