by using the io_mem RPC of the platform session instead of parsing the
bar resources manually. This commits avoids and breakage on systems where
the Intel graphic cards just uses 64bits with addresses above 4G.
Issue #4450
Compared to the bytewise memset, a wordwise memset (or even multi-word)
achieves a speedup of ~6.
On Zynq-7000/Cortex-A9:
317 MiB/s -> 2040 MiB/s
On base-linux x86_64:
3580 MiB/s -> 23700 MiB/s
genodelabs/genode#4456
Preloading a few cache lines ahead brings a significant speedup in
memcpy throughput. Note, the particular (optimal) value was empirically
determined on a Cortex-A9 (Zynq-7000) SoC @ 666Mhz. It is best combined
with L2 prefetching enabled (including double linefills and prefetch
offset 7). Yet, even without L2 prefetching this seems to be the sweet
spot.
genodelabs/genode#4456
The implementation is not in use any more. Furthermore, on typical ARM
cores such as the Cortex-A9, the cached read appears to be the
bottleneck rather than instruction density. On a Zynq-7000 SoC, the vfp
implementation performed significantly worse than the standard load/store
multiple implementation with preloading.
genodelabs/genode#4456
When executed on Linux, the test was impaired by the copy-on-write
optimisation since the source buffer was never initialised. By default,
Linux only maps a zeroed page until the first write access to the page
occurs. Since the source buffer was never written, the corresponding
page was always present in the physically-indexed data cache. In
consequence, the test merely measured write performance (similar to memset).
genodelabs/genode#4454
Send usb ctrl transfers with one second timeout as some devices (e.g.,
smartcard readers) do not response to certain control transfers.
Thanks to Peter for the investigation.
The i2c code has a busy loop (see commit for the location), which expects that
the jiffies advances without a cooperative scheduling decision.
Issue #4450
Our usb_host driver supports UHCI, OHCI, EHCI, and XHCI host
controllers. The USB4 host interface / Thunderbolt is currently not
supported and must therefore not be passed to the USB host driver.
If any PCI device reports 0 as interrupt PIN, drivers may try to force
MSI setup (e.g., xhci). So, we clamp the interrupt PIN to 1 to let
drivers finish initialization and don't bother the platform driver.
Encountered on the Fuji5 where for reasons currently unknown the
first xHCI HC (0:0d.0) could not be initialize due to incomplete
interupt informations. The other HCs appear to work fine (tested
with a USB low-speed mouse).
This commit removes all physical notions from the information given
to the Linux kernel regarding PCI BARs.
With the exception for the host bridge that needs to be located at
'0:00.0' as required by the Intel FB driver, all other devices are
announced at the PCI BUS in an ascending order.
Additionally the MMIO regions start at 1 GiB and are capped at 32 bit
to prevent unnecessary access to 64 bit addresses.
With this fix, the driver no longer aborts on the Tigerlake notebook and
just skips the out-of-region ACPI table. Issue #4452 is not fixed by
this commit, but in this specific case the table is not used anyway.
Upgrade to the well known worst cases by the GPU multiplexer. Do not
keep track of resources locally, in case resources are exceeded the
remain so anyway.
issue #4451
Check if there are a least 4 caps + 2MB (heap) + possible buffer size
available before any resource allocation. Only account resources that are
actually used.
issue #4451
The former implementation relied on the behaviour of how the old
intel fb driver requested the pci devices. The new lxkit however actually
really want to have all available pci devices.
Issue #4450
required by the upcoming update of the intel display driver. Make this addition
explicit, because it triggers adjustment also on the new pc_usb_host_drv.
Issue #4450
If size is zero, the platform goes out of service by:
[init -> platform_drv] Error: Uncaught exception of type 'Genode::Ram_allocator::Denied'
[init -> platform_drv] Warning: abort called - thread: e
Issue #4450
Also, the repository URL was adapted to the permanent redirect to github
to prevent the following warning.
dde_ipxe download http://git.ipxe.org/ipxe.git
dde_ipxe git Cloning into 'src/lib/dde_ipxe'...
dde_ipxe git warning: redirecting to https://github.com/ipxe/ipxe/
dde_ipxe update src/lib/dde_ipxe
This patch adds the trace-logger utility to the default set of packages
along with an optional launcher. With this change, only two steps are
needed to use Genode's tracing mechanism with Sculpt:
- Add 'trace_logger' to the 'launcher:' list of the .sculpt file
- Either manually select the 'trace_logger' from the '+' menu,
or add the following entry to the deploy configuration:
<start name="trace_logger"/>
By default, the trace logger is configured to trace all threads
executed in the runtime subsystem and to print a report every 10
seconds. This default policy can be refined in the launcher's <config>
node. Note that the trace logger does not respond to configuration
changes during runtime. Changes come into effect not before restarting
the component.
Issue #4448
This patch changes the output format of the trace logger to become
better suitable for human consumption. For example, when instrumenting
the VFS server in Sculpt using the GENODE_TRACE_TSC utility, the
trace logger now generates tabular output as follows.
Report 4
PD "init -> runtime -> arch_vbox6 -> vbox -> " ----------------
Thread "vCPU" at (0,0) total:12909024 recent:989229
Thread "vCPU" at (1,0) total:5643234 recent:786437
PD "init -> runtime -> ahci-0.fs" -----------------------------
Thread "ahci-0.fs" at (0,0) total:910497 recent:6335
Thread "ep" at (0,0) total:0 recent:0
71919692932: TSC process_packets: 8005M (4998 calls, last 4932K)
71921558516: TSC process_packets: 8006M (4999 calls, last 1596K)
71922760220: TSC process_packets: 8007M (5000 calls, last 1006K)
71929853586: TSC process_packets: 8009M (5001 calls, last 1840K)
71931315246: TSC process_packets: 8011M (5002 calls, last 1253K)
72127999920: TSC process_packets: 8016M (5003 calls, last 5606K)
72129568198: TSC process_packets: 8018M (5004 calls, last 1345K)
77161908178: TSC process_packets: 8029M (5005 calls, last 11349K)
77643225736: TSC process_packets: 8029M (5006 calls, last 217K)
89422100594: TSC process_packets: 8035M (5007 calls, last 5656K)
89422123632: TSC process_packets: 8035M (5008 calls, last 1342)
Thread "signal handler" at (0,0) total:36329 recent:3001
Thread "signal_proxy" at (0,0) total:51838 recent:13099
Thread "pdaemon" at (0,0) total:97184 recent:332
Thread "vdrain" at (0,0) total:1266 recent:286
Thread "vrele" at (0,0) total:1904 recent:516
PD "init -> runtime -> nic_drv" -------------------------------
Thread "nic_drv" at (0,0) total:34044 recent:897
Thread "signal handler" at (0,0) total:369 recent:142
...
Subjects that belong to the same PD are grouped together. The formerly
optional affinity and activity options have been removed. Those
information are now unconditionally displayed. The trace entries
belonging to a thread appear as slightly indented.
The patch also updates the coding style, avoiding excessively long
lines.
Issue #4448
This patch reduces repetitive log output by omitting inactive trace
subjects from the log output. The information about all subjects can
still be dumped by setting 'verbose="yes"'.
Issue #4448
This patch splits the creation and updating of monitor objects into two
stages. The creation of a monitor object changes the state of the
associated trace subject. The patch ensures that the new state is
captured by the update of the monitor object.
Issue #4448
This patch makes the trace-subject state as reflected to the trace
monitor more accurate.
Until now, a subject could be in UNTRACED or TRACED state. In reality,
however, there exists an intermediate state after the trace monitor
called 'trace' for the subject but before the subject locally activated
the tracing (done when passing a trace point). This intermediate state
was reflected as UNTRACED. Consequently, threads that never pass a trace
point (e.g., just waiting for I/O) would remain to appear as UNTRACED
even after enabling its tracing by the trace monitor. This is confusing.
This patch replaces the former UNTRACED and TRACED states by three
distinct states:
UNATTACHED prior any call of 'trace'
ATTACHED after a trace monitor called 'trace'
but before the tracing is active
TRACE tracing is active
Fixes#4447
The new macros GENODE_TRACE_TSC and GENODE_TRACE_TSC_NAMED complement
the existing GENODE_LOG_TSC and GENODE_LOG_TSC_NAMED macros to simplify
TSC measurements at a low overhead of the trace mechanism.
The utilities of the new util/formatted_output.h header complement the
existing base/output.h with the text-formatting support needed to
produce tabular output.
Fixes#4449
First, the endpoint update has to comply with the current alternate
settings of all interface, which are stored in USBDevice::altsetting[]
(one value per interface). Second, a SET_INTERFACE control request via
Packet_type::ALT_SETTING must update USBDevice::altsetting for the
interface.
Now, USB devices with multi-setting interface like the Joulescope JS110
with mixed bulk/isochronous endpoints are supported.
This commit adjusts the value such that USB sessions requested by
VirtualBox6 on Sculpt OS can get established on the first try without
invoking the session-retry mechanism. This reduces the number of
diagnostic log messages like:
Error: Insufficient 'ram_quota',got 6296372 need 6297928
The value of 50% as assigned by commit "sculpt: add basic support for
i.MX8 Quad EVK" leaves too little room for other components of the
runtime subsystem. With the adjustements of commit "sculpt: assign CPU
quotas" the sum exeedcs 100%. Hence this commit tunes down the value to
sensible 10%.
The existing assignment of CPU quotas did not anticipate the dynamic
reconfiguration of init. It merely tracked the available CPU quota by
deducing the consumed amount from a global variable but never
replenished the value. This worked for static scenarios but failed in
situations where components are dynamically re-started.
So far this deficiency remained detected because CPU quotas were not
used in highly dynamic systems like Sculpt OS. However, this has
recently changed by commit "sculpt: assign CPU quotas".
The patch improves the accounting by mirroring the existing handling of
RAM and cap quotas. Note that the CPU-quota accounting is still rather
limited. In particular the dynamic rebalancing is not yet supported.
Issue #4445
.SHELLFLAGS is extended by option pipefail to make pipes fail if any pipe
element fails. As .SHELLFLAGS is exported into sub-make instances it
must be unexported before calling third-party build systems recursively.
With the consolidation of the file-system session's signal handlers
implemented by commit "file_system_session: merge ack and submit sigh",
we can now change the VFS server to produce batches of acknowledgements
before explicitly waking up the client. (in contrast to the traditional
'acknowledge_packet', the new 'try_ack_packet' triggers no signal)
Issue #4388
Split the trace buffer into two partitions in order to prevent overwriting
of entries when the consumer is too slow. See file comment in buffer.h.
genodelabs/genode#4434
This commit simplifies the current implementation by overloading the
length field with a padding indicator in addition to the zero-length
head entry. This simplifies the iteration semantics as it eliminates
the need for determining whether a zero-length entries is the actual
head of the buffer or a padding at the buffer end.
genodelabs/genode#4434
To support device-less protocol-stacks only ports, we can use a
Virt I/O Linux kernel flavor, and export the lx_kit/lx_emul parts
not depending on platform API and devices.
Ref #4397
* Drivers have to use lx_kit/memory_dma.cc
* Protocol-stacks use lx_kit/memory_non_dma.cc
* Moreover the device-dependent lx_emul parts get removed
from the common lx_emul import rules
Fix#4443
* Unifies the declaration of callbacks which manage driver/client
shared dataspaces
* Move the Linux driver-specific callback implementation to the
lx_emul library from the PC's USB host driver
Fixgenodelabs/genode#4439
The logic got accidentally reversed during the transition from the
legacy USB driver.
Since the function drops error details, this patch adds a diagnostic
message with the error code as returned by the Linux driver.
This patch declares that the pseudo target virtualbox6/services/ does
not produce any build artifact. This allows the adding of virtualbox6
to Sculpt's 'build:' list.
The run script uses core, ld.lib.so, and init from depot packages, thus
these cannot be integrated in the image explicitly from the build
directory.
Also, removed special build of report_rom, which is not subject of the
test.
Fixes#4437
* The problem occured only on OKL4, seL4, and L4/Fiasco
* The test used to continue submitting packets regardless of how many were in
flight
* This commit limits the in-flight packets at the Uplink/Nic connections to 40
each
Ref #4419
This commit changes the touch-click filter to adhere the following
sequence:
touch (physical)
press (artifically generated)
release (artificially generated)
release_touch (physical)
This order is important because nitpicker's focus handling takes
press/release events into account. If the release-touch event appears
before the release event, nitpicker subsumes the release-touch event
to the sequence that started with the press event, instead of handling
it as a free-standing event.
Issue #4332
By assigning CPU budgets, base-hw's priorities come into effect.
Even though the chosen values are rather guessed than informed, they
yield a visibly improved responsiveness on the Pinephone.
When committing a new entry, the buffer wrapped if the last entry fit
perfectly into the buffer. Otherwise, the length field of the next entry
was set to 0 to mark the new head. Yet, if there was still some padding but not
enough to hold the length field of another entry, we ended up with a
headless buffer.
genodelabs/genode#4430
Since the head of the buffer is marked by a zero-length entry, we must
only write the length field if a new head was set. Otherwise, the
consumer might already read the new entry and not find the new head as a stop
condition.
genodelabs/genode#4430
When a device got already acquired by a platform session client, do not
return the same capability again, even if the same platform session
client requested it. Therefore, make doubtful behaviour of client components
visible, and do not have to struggle with Platform::Device instances
instantiated multiple times, which care of the lifetime of the device
capability internally.
Fixgenodelabs/genode#4379
Genode code already expects MMU to be disabled when starting the
kernel. It is enabled eventually in Bootstrap::Platform::enable_mmu,
after setting up translation tables. Unfortunately nothing ensures
this is actually the case. If MMU happens to be enabled when entering
the kernel things go downhill pretty fast after we start messing with
TTBR.
This patch ensures MMU is disabled for EL1, EL2, EL3 dependent on the
exception level of the CPU core, which is entering the kernel.
This should allow base-hw to start correctly on Quartz64 A board.
The `lookup_translation` function got introduced and is used only in the
context to proof whether a cache maintainance function can be executed
safely by the kernel. Unfortunately, it did not checked write permissions,
which can lead to permission faults. This commit restricts the lookup
function to only succeed when the target page is writeable. Consequently,
the lookup function gets renamed to `lookup_rw_translation`.
Fixgenodelabs/genode#4348
* Switch from the legacy usb_host driver to the new PC version
in recipes and automated tests
* Update documentation snippets
* Remove outdated, unused usb_rndis run-script
Fixgenodelabs/genode#4416
Do not only report devices, but the current configuration of the driver too,
as long as the `report` node in the configuration states it.
Ref genodelabs/genode#4416
To stay consistent with the configuration of the legacy usb_host_drv
and other components as well, do not report USB devices by default,
but when the following XML node is set within the component's
configuration:
<report devices="yes"/>
Ref genodelabs/genode#4416
The new usb_host driver for PC by default needs more RAM quota in contrast
to the old one. To minor warnings and repeated attempts to open a USB
session from a client, this commit increases the default RAM quota by one
page.
Ref genodelabs/genode#4416
Adds a function to the USB part of the Genode's C API, to enable
usb_host drivers to acknowledge USB request in client's packet buffer
although they are not assigned to an USB device. The requests are
marked with a "no device" error.
This commit fixes a regression originally solved in genodelabs/genode#4149
Ref genodelabs/genode#4416
XML allows attribute values like <node attr="\"/>. The XML parser
wrongly reflects this case as 'Invalid_syntax'. This behavior stems from
the implicit use of the 'end_of_quote' function, which considers the
sequence of '\"' as a quoted '"' rather than the end of a quoted string.
The patch solves this problem by making the 'end_of_quote' part of
the tokenizer's scanner policy.
The patch removes the 'end_of_quote' function from 'util/string.h'
because it is not universal, and to avoid the ambiguity with
'SCANNER_POLICY::end_of_quote'.
Fixes#4431
When a PD owns the right to ask for a RAM dataspace's `dma_addr` it is
concurrently constrained to use allocations of a specific physical RAM area.
This commit further limits this area by removing RAM page frame zero.
Otherwise the return value of `dma_addr` for such a dataspace would be
erroneously interpreted as a fault, because zero is currently the error
return value of `dma_addr`.
Fixgenodelabs/genode#4428
This patch cuts the superfluous dependency of abi.so files from the
library dependencies of the corresponding lib.so file. ABIs depend
only on symbol files.
Prior this patch, the second step of the following sequence would
wrongly re-build the abi.so file.
arm_v6$ make init
arm_v6$ make init KERNEL=hw
As the KERNEL argument does not affect the ABI, the abi.so should
better not be created twice.
Issue #4408
The Single_file_system now forwards the
`File_io_service::notify_read_ready` method to the
handle as it already did for most of the other methods.
genodelabs/genode#4394
Do not set '_mode' per default to MANANGED. Check if a manual config ROM
is present during construction and set '_mode' to MANUAL in case it is.
issue #4369
'generate(Xml_node node)', as used by the Sculpt manager, calls this
function instead of the lambda version. The 'report' function of the
'Genode::Reporter' does not throw an exception in case there is not
enough backing storage for the 'generate' request. Therefore, we have to
check this condition in a loop and call '_increase_report_buffer' in
case size limits are reached.
Patch by Norman Feske.
issue #4369
Genode linker does not support .gnu.hash tables so they will never be
used. Tell the linker not to bother producing them. This should reduce
the size of Genode ELF files a tiny bit without loosing anything
important in the process.
Fixes#4423
According to ARM Cortex-A55 Core Technical Reference Manual r1p0 the
lowest 8 bits (Aff0) of MPIDR register represent thread IDs within a
multi-threaded core. The actual core identification bits are in Aff1.
This layout can be identified by checking the MT bit of MPIDR register.
Basically, if MT=1 core id is in Aff1, if MT=0 core id is in Aff0.
Without this change Genode will identify all CPU cores on A55 as primary
(0) core.
Its worth to mention that Cortex-A55 by itself is not a multi-threaded
CPU. Aff0 values are always expected to be 0 for pure A55 cores. A55
cores can however be paired with cores that are multi-threaded. To
support such big.LITTLE CPUs in Genode we'd probably need to add a
different mechanism for mapping MPIDR values to logical, contignous
core IDs which Genode expects.
Ref:
https://developer.arm.com/documentation/100442/0100/register-descriptions/aarch64-system-registers/mpidr-el1--multiprocessor-affinity-register--el1?lang=en
* use netperf omnitest output selectors to acquire more metrics
* remove packet_size argument that was not interpreted by netperf
genodelabs/genode#4427
This does not affect default Genode builds as far as I can tell. There
is always at least one global static CTOR which seems to be coming from
one of the GCC runtime libs bundled in the toolchain. The problem became
visible for me only after I've replated GCC runtime with LLVM based
one. In such setup I often see binaries that do not have any static ctors.
Such binaries end up crashing Genode ld.lib.so.
Make sure the code does handle empty constructors array.
Fixes#4422
Switch the code to 0 lengh array instead. The code in
Lru_cache::element_size calls sizeof on this structure. This works in
gcc, but fails when using clang. Even for GCC however the documentation
states:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."
Basically its an implementation quirk that clang does not support. Both
GCC and clang do support zero sized arrays however so using them here
allows both compilers to process this code.
Ref: https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
Issue #4421
This reference member is not used anywhere in the code. This prompts
clang to complain about it. Eliminate the member and all the plumbing
associated with it to silence the warning.
Issue #4421
Clang really doesn't like char subscripts. I can't say I blame it. Fix
the warning by an explicit cast to unsigned.
include/nitpicker_gfx/tff_font.h:230:53: error:
array subscript is of type 'char' [-Werror,-Wchar-subscripts]
Tff::Vertical_metrics const m = _vertical_metrics['m'];
^~~~
Issue #4421
Clang likes to complain when lambdas capture parameters without
actually using them. This patch fixes a couple of such problems in VFS
related os module code.
Issue #4421
The soft ABI implies purely software floating point implementation.
This is not the case for Genode however. For example core's
exception_vector.S uses vmsr instruction. This builds fine with with
GCC based toolchain, but clang with integrated-as complains:
src/core/spec/arm/exception_vector.S:122:2: error: instruction requires: VFP2
vmsr fpexc, r1
^
Fix this by passing softfp to mfloat-abi command on ARMv7. This allows
usage of FP HW, but implies soft-floating point ABI.
Issue #4421
According to C++11 reference:
"If the strictest (largest) alignas on a declaration is weaker than
the alignment it would have without any alignas specifiers (that is,
weaker than its natural alignment or weaker than alignas on another
declaration of the same object or type), the program is ill-formed:"
https://en.cppreference.com/w/cpp/language/alignas
The code requests 4 byte alignment for Genode::Arm_cpu::Context.
The Context structure inherits Genode::Arm_cpu::Fpu_context which
has minimum alignment requirement of 8 bytes, due to uint64_t d0_d31
member. This makes the 4 byte value in Context's alignas specifier
invalid (smaller than allowed minimum).
Similar situation takes place in Arm_64 case. The claimed minimum
alignment of Context is 8 bytes, but the fpu_state member imposes 16
bytes alignment (explicitly specified in Fpu_state declaration).
In both cases the code builds fine with GCC 8.3.0, but fails with
clang which claims that "requested alignment is less than minimum
alignment of X for type", where X is 8 on ARM and 16 on AArch64.
Ref: https://eel.is/c++draft/dcl.align#5
Issue #4421
This commit contains:
* Minimal Linux kernel target: pc_linux
* Library to generate a Linux build directory, config, generated headers
* API depot package
The actual work was provided by Josef Soentgen.
Ref genodelabs/genode#4416
The official way to obtain DMA addresses for RAM dataspaces is
the RPC function 'Pd_session::dma_addr' now. User-level device drivers
should not call this function directly but use the 'Platform_session'
interface of the platform driver instead.
Fixes#2243
* Creates sessions to all supported services of the black hole component
* Test-drives the Event and Capture session with dummy input
* Adds the test to the default list of depot_autopilot.run
* Test-driving the Audio_in and Audio_out sessions is still missing and should
be added via a dedicated commit
Ref #4419
To make room for the re-newed usb_host_drv basing on Linux 5.14 and
the re-newed lx_kit/lx_emul we have to move the depot recipe and
consistently name the old drivers with a legacy_ prefix.
Ref genodelabs/genode#4416
The x86 platform driver uses a different API than the one for ARM for
which the lx_kit glue code was designed. Since the x86 platform driver
will eventually adopt a similar interface we implement a wrapper that
encapsulates the old interface.
Ref genodelabs/genode#4411
Until now, the lx_emul layer addressed a 5.11 Linux Kernel port,
now that we add new architectures it is better to update the default version
first. There are especially changes in the task_struct code,
and the signature of some functions in the paging subsystem changed.
Ref genodelabs/genode#4411
We use the architecture-specific setjmp/longjmp implementation without
modification in the newer lx_kit implementation as well. There is no
need for a duplication.
Ref genodelabs/genode#4411
In the error case of socket_fs_accept() the Unconfirmed utility was
incompletely applied with the result of executing the cleanup routines
in the wrong order.
Fixes#4417
This patch removes the implicit build of ld-$(KERNEL) by the generic
ld.mk file because the kernel-specific dynamic linker is unreachable
when building a regular binary archive.
Issue #4320
When 'KERNEL' is specified, let the generic (pseudo) target of
lib/mk/ld.mk trigger the build of the actual dynamic linker named after
the used kernel. This way, we become able to remove the magic
linker-build step from the boot-image stage of the run tool.
Issue #4320
This patch applies the existing "privatization" of transitive
shared-library dependencies from static lib dependencies to shared lib
dependencies. It thereby improves the consistency of binaries created in
a regular build directory with binaries created in depot archives.
Issue #4408
This patch makes nitpicker's "clicked" report useful for the detection
of clicks outside of any client. This is needed in situations where the
dialog should close when clicking outside its screen area. In the new
version, a click outside any client results in a report without a
'label' attribute. Furthermore, the report is augmented by the sequence
number of the click, which allows for freshness checks by the consumer of
the report (i.e., sculpt_manager).
Issue #4398
If the buffer contains padding at the end, the iteration must continue
in order to restart iteration from the start of the buffer.
genodelabs/genode#4244
The archive contents are equivalent except the creation date of the
top-level directory.
-drwxr-xr-x guivol/users 0 2021-01-07 12:54 jpeg-9d/
+drwxr-xr-x guivol/users 0 2022-01-04 12:02 jpeg-9d/
Fixes#4406
The functionality of the test-block-client, test-block-server, and
test-block-bench components is now covered by the block_tester
application and the vfs_block server.
Issue #4405
This patch eliminates warnings that occurred as side effect of using the
'Session_policy' utility ("Warning: no policy defined for label...").
The new version uses the 'with_matching_policy' function instead, which
has the nice side effect of simplifying the error handling.
This patch makes the server-side policy-matching logic available outside
the 'Session_policy' class. Given that the new 'with_matching_policy'
function does not throw any exception, it gives server implementations
the freedom to avoid the C++ exception mechanism for the policy handling.
If the platform driver lacks the 'managing_system="yes"' attribute,
requests for DMA addresses return 0. This patch is meant to help
diagnosing such configuration issues.
Issue #2243
