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The Tegra IOVMM is an interface to allow device drivers and subsystems in the kernel to manage the virtual memory spaces visible to I/O devices. The interface has been designed to be scalable to allow for I/O virtual memory hardware which exists in one or more limited apertures of the address space (e.g., a small aperture in physical address space which can perform MMU-like remapping) up to complete virtual addressing with multiple address spaces and memory protection. The interface has been designed to be similar to the Linux virtual memory system; however, operations which would be difficult to implement or nonsensical for DMA devices (e.g., copy-on-write) are not present, and APIs have been added to allow for management of multiple simultaneous active address spaces. The API is broken into four principal objects: areas, clients, domains and devices. Areas ===== An area is a contiguous region of the virtual address space which can be filled with virtual-to-physical translations (and, optionally, protection attributes). The virtual address of the area can be queried and used for DMA operations by the client which created it. As with the Linux vm_area structures, it is the responsibility of whichever code creates an area to ensure that it is populated with appropriate translations. Domains ======= A domain in the IOVMM system is similar to a process in a standard CPU virtual memory system; it represents the entire range of virtual addresses which may be allocated and used for translation. Depending on hardware capabilities, one or more domains may be resident and available for translation. IOVMM areas are allocated from IOVMM domains. Whenever a DMA operation is performed to or from an IOVMM area, its parent domain must be made resident prior to commencing the operation. Clients ======= I/O VMM clients represent any entity which needs to be able to allocate and map system memory into I/O virtual space. Clients are created by name and may be created as part of a "share group," where all clients created in the same share group will observe the same I/O virtual space (i.e., all will use the same IOVMM domain). This is similar to threads inside a process in the CPU virtual memory manager. The callers of the I/O VMM system are responsible for deciding on the granularity of client creation and share group definition; depending on the specific usage model expected by the caller, it may be appropriate to create an IOVMM client per task (if the caller represents an ioctl'able interface to user land), an IOVMM client per driver instance, a common IOVMM client for an entire bus, or a global IOVMM client for an OS subsystem (e.g., the DMA mapping interface). Each client is responsible for ensuring that its IOVMM client's translation is resident on the system prior to performing DMA operations using the IOVMM addresses. This is accomplished by preceding all DMA operations for the client with a call to tegra_iovmm_client_lock (or tegra_iovmm_client_trylock), and following all operations (once complete) with a call to tegra_iovmm_client_unlock. In this regard, clients are cooperatively context- switched, and are expected to behave appropriately. Devices ======= I/O VMM devices are the physical hardware which is responsible for performing the I/O virtual-to-physical translation. Devices are responsible for domain management: the mapping and unmapping operations needed to make translations resident in the domain (including any TLB shootdown or cache invalidation needed to ensure coherency), locking and unlocking domains as they are made resident by clients into the devices' address space(s), and allocating and deallocating the domain objects. Devices are responsible for the allocation and deallocation of domains to allow coalescing of multiple client share groups into a single domain. For example, if the device's hardware only allows a single address space to be translated system-wide, performing full flushes and invalidates of the translation at every client switch may be prohibitively expensive. In these circumstances, a legal implementation of the IOVMM interface includes returning the same domain for all clients on the system (regardless of the originally-specified share group). In this respect, a client can be assured that it will share an address space with all of the other clients in its share group; however, it may also share this address space with other clients, too. Multiple devices may be present in a system; a device should return a NULL domain if it is incapable of servicing the client when it is asked to allocate a domain. ---------------------------------------------------------------------------- IOVMM Client API ================ tegra_iovmm_alloc_client - Called to create a new IOVMM client object; the implementation may create a new domain or return an existing one depending on both the device and the share group. tegra_iovmm_free_client - Frees a client. tegra_iovmm_client_lock - Makes a client's translations resident in the IOVMM device for subsequent DMA operations. May block if the device is incapable of context-switching the client when it is called. Returns -EINTR if the waiting thread is interrupted before the client is locked. tegra_iovmm_client_trylock - Non-blocking version of tegra_iovmm_client_lock tegra_iovmm_client_unlock - Called by clients after DMA operations on IOVMM- translated addresses is complete; allows IOVMM system to context-switch the current client out of the device if needed. tegra_iovmm_create_vm - Called to allocate an IOVMM area. If lazy / demand-loading of pages is desired, clients should supply a pointer to a tegra_iovmm_area_ops structure providing callback functions to load, pin and unpin the physical pages which will be mapped into this IOVMM region. tegra_iovmm_get_vm_size - Called to query the total size of an IOVMM client tegra_iovmm_free_vm - Called to free a IOVMM area, releasing any pinned physical pages mapped by it and to decommit any resources (memory for PTEs / PDEs) required by the VM area. tegra_iovmm_vm_insert_pfn - Called to insert an exact pfn (system memory physical page) into the area at a specific virtual address. Illegal to call if the IOVMM area was originally created with lazy / demand-loading. tegra_iovmm_zap_vm - Called to mark all mappings in the IOVMM area as invalid / no-access, but continues to consume the I/O virtual address space. For lazy / demand-loaded IOVMM areas, a zapped region will not be reloaded until it has been unzapped; DMA operations using the affected translations may fault (if supported by the device). tegra_iovmm_unzap_vm - Called to re-enable lazy / demand-loading of pages for a previously-zapped IOVMM area. tegra_iovmm_find_area_get - Called to find the IOVMM area object corresponding to the specified I/O virtual address, or NULL if the address is not allocated in the client's address space. Increases the reference count on the IOVMM area object tegra_iovmm_area_get - Called to increase the reference count on the IOVMM area object tegra_iovmm_area_put - Called to decrease the reference count on the IOVMM area object IOVMM Device API ================ tegra_iovmm_register - Called to register a new IOVMM device with the IOVMM manager tegra_iovmm_unregister - Called to remove an IOVMM device from the IOVMM manager (unspecified behavior if called while a translation is active and / or in-use) tegra_iovmm_domain_init - Called to initialize all of the IOVMM manager's data structures (block trees, etc.) after allocating a new domain IOVMM Device HAL ================ map - Called to inform the device about a new lazy-mapped IOVMM area. Devices may load the entire VM area when this is called, or at any time prior to the completion of the first read or write operation using the translation. unmap - Called to zap or to decommit translations map_pfn - Called to insert a specific virtual-to-physical translation in the IOVMM area lock_domain - Called to make a domain resident; should return 0 if the domain was successfully context-switched, non-zero if the operation can not be completed (e.g., all available simultaneous hardware translations are locked). If the device can guarantee that every domain it allocates is always usable, this function may be NULL. unlock_domain - Releases a domain from residency, allows the hardware translation to be used by other domains. alloc_domain - Called to allocate a new domain; allowed to return an existing domain free_domain - Called to free a domain. Change-Id: Ic65788777b7aba50ee323fe16fd553ce66c4b87c Signed-off-by: Gary King <gking@nvidia.com>
Linux kernel release 2.6.xx <http://kernel.org/>
These are the release notes for Linux version 2.6. Read them carefully,
as they tell you what this is all about, explain how to install the
kernel, and what to do if something goes wrong.
WHAT IS LINUX?
Linux is a clone of the operating system Unix, written from scratch by
Linus Torvalds with assistance from a loosely-knit team of hackers across
the Net. It aims towards POSIX and Single UNIX Specification compliance.
It has all the features you would expect in a modern fully-fledged Unix,
including true multitasking, virtual memory, shared libraries, demand
loading, shared copy-on-write executables, proper memory management,
and multistack networking including IPv4 and IPv6.
It is distributed under the GNU General Public License - see the
accompanying COPYING file for more details.
ON WHAT HARDWARE DOES IT RUN?
Although originally developed first for 32-bit x86-based PCs (386 or higher),
today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
Xtensa, AVR32 and Renesas M32R architectures.
Linux is easily portable to most general-purpose 32- or 64-bit architectures
as long as they have a paged memory management unit (PMMU) and a port of the
GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
also been ported to a number of architectures without a PMMU, although
functionality is then obviously somewhat limited.
Linux has also been ported to itself. You can now run the kernel as a
userspace application - this is called UserMode Linux (UML).
DOCUMENTATION:
- There is a lot of documentation available both in electronic form on
the Internet and in books, both Linux-specific and pertaining to
general UNIX questions. I'd recommend looking into the documentation
subdirectories on any Linux FTP site for the LDP (Linux Documentation
Project) books. This README is not meant to be documentation on the
system: there are much better sources available.
- There are various README files in the Documentation/ subdirectory:
these typically contain kernel-specific installation notes for some
drivers for example. See Documentation/00-INDEX for a list of what
is contained in each file. Please read the Changes file, as it
contains information about the problems, which may result by upgrading
your kernel.
- The Documentation/DocBook/ subdirectory contains several guides for
kernel developers and users. These guides can be rendered in a
number of formats: PostScript (.ps), PDF, HTML, & man-pages, among others.
After installation, "make psdocs", "make pdfdocs", "make htmldocs",
or "make mandocs" will render the documentation in the requested format.
INSTALLING the kernel source:
- If you install the full sources, put the kernel tarball in a
directory where you have permissions (eg. your home directory) and
unpack it:
gzip -cd linux-2.6.XX.tar.gz | tar xvf -
or
bzip2 -dc linux-2.6.XX.tar.bz2 | tar xvf -
Replace "XX" with the version number of the latest kernel.
Do NOT use the /usr/src/linux area! This area has a (usually
incomplete) set of kernel headers that are used by the library header
files. They should match the library, and not get messed up by
whatever the kernel-du-jour happens to be.
- You can also upgrade between 2.6.xx releases by patching. Patches are
distributed in the traditional gzip and the newer bzip2 format. To
install by patching, get all the newer patch files, enter the
top level directory of the kernel source (linux-2.6.xx) and execute:
gzip -cd ../patch-2.6.xx.gz | patch -p1
or
bzip2 -dc ../patch-2.6.xx.bz2 | patch -p1
(repeat xx for all versions bigger than the version of your current
source tree, _in_order_) and you should be ok. You may want to remove
the backup files (xxx~ or xxx.orig), and make sure that there are no
failed patches (xxx# or xxx.rej). If there are, either you or me has
made a mistake.
Unlike patches for the 2.6.x kernels, patches for the 2.6.x.y kernels
(also known as the -stable kernels) are not incremental but instead apply
directly to the base 2.6.x kernel. Please read
Documentation/applying-patches.txt for more information.
Alternatively, the script patch-kernel can be used to automate this
process. It determines the current kernel version and applies any
patches found.
linux/scripts/patch-kernel linux
The first argument in the command above is the location of the
kernel source. Patches are applied from the current directory, but
an alternative directory can be specified as the second argument.
- If you are upgrading between releases using the stable series patches
(for example, patch-2.6.xx.y), note that these "dot-releases" are
not incremental and must be applied to the 2.6.xx base tree. For
example, if your base kernel is 2.6.12 and you want to apply the
2.6.12.3 patch, you do not and indeed must not first apply the
2.6.12.1 and 2.6.12.2 patches. Similarly, if you are running kernel
version 2.6.12.2 and want to jump to 2.6.12.3, you must first
reverse the 2.6.12.2 patch (that is, patch -R) _before_ applying
the 2.6.12.3 patch.
You can read more on this in Documentation/applying-patches.txt
- Make sure you have no stale .o files and dependencies lying around:
cd linux
make mrproper
You should now have the sources correctly installed.
SOFTWARE REQUIREMENTS
Compiling and running the 2.6.xx kernels requires up-to-date
versions of various software packages. Consult
Documentation/Changes for the minimum version numbers required
and how to get updates for these packages. Beware that using
excessively old versions of these packages can cause indirect
errors that are very difficult to track down, so don't assume that
you can just update packages when obvious problems arise during
build or operation.
BUILD directory for the kernel:
When compiling the kernel all output files will per default be
stored together with the kernel source code.
Using the option "make O=output/dir" allow you to specify an alternate
place for the output files (including .config).
Example:
kernel source code: /usr/src/linux-2.6.N
build directory: /home/name/build/kernel
To configure and build the kernel use:
cd /usr/src/linux-2.6.N
make O=/home/name/build/kernel menuconfig
make O=/home/name/build/kernel
sudo make O=/home/name/build/kernel modules_install install
Please note: If the 'O=output/dir' option is used then it must be
used for all invocations of make.
CONFIGURING the kernel:
Do not skip this step even if you are only upgrading one minor
version. New configuration options are added in each release, and
odd problems will turn up if the configuration files are not set up
as expected. If you want to carry your existing configuration to a
new version with minimal work, use "make oldconfig", which will
only ask you for the answers to new questions.
- Alternate configuration commands are:
"make config" Plain text interface.
"make menuconfig" Text based color menus, radiolists & dialogs.
"make xconfig" X windows (Qt) based configuration tool.
"make gconfig" X windows (Gtk) based configuration tool.
"make oldconfig" Default all questions based on the contents of
your existing ./.config file and asking about
new config symbols.
"make silentoldconfig"
Like above, but avoids cluttering the screen
with questions already answered.
Additionally updates the dependencies.
"make defconfig" Create a ./.config file by using the default
symbol values from either arch/$ARCH/defconfig
or arch/$ARCH/configs/${PLATFORM}_defconfig,
depending on the architecture.
"make ${PLATFORM}_defconfig"
Create a ./.config file by using the default
symbol values from
arch/$ARCH/configs/${PLATFORM}_defconfig.
Use "make help" to get a list of all available
platforms of your architecture.
"make allyesconfig"
Create a ./.config file by setting symbol
values to 'y' as much as possible.
"make allmodconfig"
Create a ./.config file by setting symbol
values to 'm' as much as possible.
"make allnoconfig" Create a ./.config file by setting symbol
values to 'n' as much as possible.
"make randconfig" Create a ./.config file by setting symbol
values to random values.
You can find more information on using the Linux kernel config tools
in Documentation/kbuild/kconfig.txt.
NOTES on "make config":
- having unnecessary drivers will make the kernel bigger, and can
under some circumstances lead to problems: probing for a
nonexistent controller card may confuse your other controllers
- compiling the kernel with "Processor type" set higher than 386
will result in a kernel that does NOT work on a 386. The
kernel will detect this on bootup, and give up.
- A kernel with math-emulation compiled in will still use the
coprocessor if one is present: the math emulation will just
never get used in that case. The kernel will be slightly larger,
but will work on different machines regardless of whether they
have a math coprocessor or not.
- the "kernel hacking" configuration details usually result in a
bigger or slower kernel (or both), and can even make the kernel
less stable by configuring some routines to actively try to
break bad code to find kernel problems (kmalloc()). Thus you
should probably answer 'n' to the questions for
"development", "experimental", or "debugging" features.
COMPILING the kernel:
- Make sure you have at least gcc 3.2 available.
For more information, refer to Documentation/Changes.
Please note that you can still run a.out user programs with this kernel.
- Do a "make" to create a compressed kernel image. It is also
possible to do "make install" if you have lilo installed to suit the
kernel makefiles, but you may want to check your particular lilo setup first.
To do the actual install you have to be root, but none of the normal
build should require that. Don't take the name of root in vain.
- If you configured any of the parts of the kernel as `modules', you
will also have to do "make modules_install".
- Verbose kernel compile/build output:
Normally the kernel build system runs in a fairly quiet mode (but not
totally silent). However, sometimes you or other kernel developers need
to see compile, link, or other commands exactly as they are executed.
For this, use "verbose" build mode. This is done by inserting
"V=1" in the "make" command. E.g.:
make V=1 all
To have the build system also tell the reason for the rebuild of each
target, use "V=2". The default is "V=0".
- Keep a backup kernel handy in case something goes wrong. This is
especially true for the development releases, since each new release
contains new code which has not been debugged. Make sure you keep a
backup of the modules corresponding to that kernel, as well. If you
are installing a new kernel with the same version number as your
working kernel, make a backup of your modules directory before you
do a "make modules_install".
Alternatively, before compiling, use the kernel config option
"LOCALVERSION" to append a unique suffix to the regular kernel version.
LOCALVERSION can be set in the "General Setup" menu.
- In order to boot your new kernel, you'll need to copy the kernel
image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
to the place where your regular bootable kernel is found.
- Booting a kernel directly from a floppy without the assistance of a
bootloader such as LILO, is no longer supported.
If you boot Linux from the hard drive, chances are you use LILO which
uses the kernel image as specified in the file /etc/lilo.conf. The
kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
/boot/bzImage. To use the new kernel, save a copy of the old image
and copy the new image over the old one. Then, you MUST RERUN LILO
to update the loading map!! If you don't, you won't be able to boot
the new kernel image.
Reinstalling LILO is usually a matter of running /sbin/lilo.
You may wish to edit /etc/lilo.conf to specify an entry for your
old kernel image (say, /vmlinux.old) in case the new one does not
work. See the LILO docs for more information.
After reinstalling LILO, you should be all set. Shutdown the system,
reboot, and enjoy!
If you ever need to change the default root device, video mode,
ramdisk size, etc. in the kernel image, use the 'rdev' program (or
alternatively the LILO boot options when appropriate). No need to
recompile the kernel to change these parameters.
- Reboot with the new kernel and enjoy.
IF SOMETHING GOES WRONG:
- If you have problems that seem to be due to kernel bugs, please check
the file MAINTAINERS to see if there is a particular person associated
with the part of the kernel that you are having trouble with. If there
isn't anyone listed there, then the second best thing is to mail
them to me (torvalds@linux-foundation.org), and possibly to any other
relevant mailing-list or to the newsgroup.
- In all bug-reports, *please* tell what kernel you are talking about,
how to duplicate the problem, and what your setup is (use your common
sense). If the problem is new, tell me so, and if the problem is
old, please try to tell me when you first noticed it.
- If the bug results in a message like
unable to handle kernel paging request at address C0000010
Oops: 0002
EIP: 0010:XXXXXXXX
eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
ds: xxxx es: xxxx fs: xxxx gs: xxxx
Pid: xx, process nr: xx
xx xx xx xx xx xx xx xx xx xx
or similar kernel debugging information on your screen or in your
system log, please duplicate it *exactly*. The dump may look
incomprehensible to you, but it does contain information that may
help debugging the problem. The text above the dump is also
important: it tells something about why the kernel dumped code (in
the above example it's due to a bad kernel pointer). More information
on making sense of the dump is in Documentation/oops-tracing.txt
- If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
as is, otherwise you will have to use the "ksymoops" program to make
sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
This utility can be downloaded from
ftp://ftp.<country>.kernel.org/pub/linux/utils/kernel/ksymoops/ .
Alternately you can do the dump lookup by hand:
- In debugging dumps like the above, it helps enormously if you can
look up what the EIP value means. The hex value as such doesn't help
me or anybody else very much: it will depend on your particular
kernel setup. What you should do is take the hex value from the EIP
line (ignore the "0010:"), and look it up in the kernel namelist to
see which kernel function contains the offending address.
To find out the kernel function name, you'll need to find the system
binary associated with the kernel that exhibited the symptom. This is
the file 'linux/vmlinux'. To extract the namelist and match it against
the EIP from the kernel crash, do:
nm vmlinux | sort | less
This will give you a list of kernel addresses sorted in ascending
order, from which it is simple to find the function that contains the
offending address. Note that the address given by the kernel
debugging messages will not necessarily match exactly with the
function addresses (in fact, that is very unlikely), so you can't
just 'grep' the list: the list will, however, give you the starting
point of each kernel function, so by looking for the function that
has a starting address lower than the one you are searching for but
is followed by a function with a higher address you will find the one
you want. In fact, it may be a good idea to include a bit of
"context" in your problem report, giving a few lines around the
interesting one.
If you for some reason cannot do the above (you have a pre-compiled
kernel image or similar), telling me as much about your setup as
possible will help. Please read the REPORTING-BUGS document for details.
- Alternately, you can use gdb on a running kernel. (read-only; i.e. you
cannot change values or set break points.) To do this, first compile the
kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
You can now use all the usual gdb commands. The command to look up the
point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
with the EIP value.)
gdb'ing a non-running kernel currently fails because gdb (wrongly)
disregards the starting offset for which the kernel is compiled.