The HW-kernel, in contrast to other kernels, provides a direct reference
to the pager object with the fault signal that is send to the pager
activation. When accessing this reference directly we may fall into the
time span where the root parent-entrypoint of the faulter has alredy
dissolved the pager object from the pager entrypoint, but not yet
silenced the according signal context. To avoid this we issue an
additional 'lookup_and_lock' with the received pager object. This isn't
optimal as we don't need the potentially cost-intensive lookup but only the
synchronization.
Fixes#1311.
Fixes#1332.
On base-hw, each thread owns exactly one scheduling context for its
whole lifetime. However, introducing helping on IPC, a thread might get
executed on scheduling contexts that it doesn't own. Figuratively
spoken, the IPC-helping relation spans trees between threads. These
trees are identical to those of the IPC relation between threads. The
root of such a tree is executed on all scheduling contexts in the tree.
All other threads in the tree are not executed on any scheduling context
as long as they remain in this position. Consequently, the ready-state
of all scheduling contexts in an IPC-helping tree always equals the
state of the root context.
fix#1102
As soon as helping is used, a thread may also be in a blocking state when its
scheduling context is ready. Hence, the state designation SCHEDULED for an active
thread would be pretty misleading.
ref #1102
On the Versatile Express Cortex A9x4 platform the first memory region
0x0 - 0x4000000 is a hardware remapped memory area, containing flash
and DDR RAM copies and thus should not be added in addition to all
DDR RAM regions and the SRAM region.
In the init configuration one can configure the donation of CPU time via
'resource' tags that have the attribute 'name' set to "CPU" and the
attribute 'quantum' set to the percentage of CPU quota that init shall
donate. The pattern is the same as when donating RAM quota.
! <start name="test">
! <resource name="CPU" quantum="75"/>
! </start>
This would cause init to try donating 75% of its CPU quota to the child
"test". Init and core do not preserve CPU quota for their own
requirements by default as it is done with RAM quota.
The CPU quota that a process owns can be applied through the thread
constructor. The constructor has been enhanced by an argument that
indicates the percentage of the programs CPU quota that shall be granted
to the new thread. So 'Thread(33, "test")' would cause the backing CPU
session to try to grant 33% of the programs CPU quota to the thread
"test". By now, the CPU quota of a thread can't be altered after
construction. Constructing a thread with CPU quota 0 doesn't mean the
thread gets never scheduled but that the thread has no guaranty to receive
CPU time. Such threads have to live with excess CPU time.
Threads that already existed in the official repositories of Genode were
adapted in the way that they receive a quota of 0.
This commit also provides a run test 'cpu_quota' in base-hw (the only
kernel that applies the CPU-quota scheme currently). The test basically
runs three threads with different physical CPU quota. The threads simply
count for 30 seconds each and the test then checks wether the counter
values relate to the CPU-quota distribution.
fix#1275
On Arndale, the kernel timer resets to the initial value of the last
count-down and continues as soon as it reaches zero. We must check this
via the interrupt status when we read out the timer value and in case
return 0 instead of the real value.
fix#1299
Kernel::Processor was a confusing remnant from the old scheme where we had a
Processor_driver (now Genode::Cpu) and a Processor (now Kernel::Cpu).
This commit also updates the in-code documentation and the variable and
function naming accordingly.
fix#1274
The run test 'hw_info' prints the content of the basic ARMv7 identification and
feature registers in a pretty readable format. It is a kernel-internal test
because many of these registers are restricted to privilege level 1 or higher.
fix#1278
The new scheduler serves the orthogonal requirements of both
high-throughput-oriented scheduling contexts (shortly called fill in the
scheduler) and low-latency-oriented scheduling contexts (shortly called
claim in the scheduler). Thus it knows two scheduling modes. Every claim
owns a CPU-time-quota expressed as percentage of a super period
(currently 1 second) and a priority that is absolute as long as the
claim has quota left for the current super period. At the end of a super
period the quota of all claims gets refreshed. During a super period,
the claim mode is dominant as long as any active claim has quota left.
Every time this isn't the case, the scheduler switches to scheduling of
fills. Fills are scheduled in a simple round robin with identical time
slices. Order and time-slices of the fill scheduling are not affected by
the super period. Now on thread creation, two arguments, priority and
quota are needed. If quota is 0, the new thread participates in CPU
scheduling with a fill only. Otherwise he participates with both a
claim and a fill. This concept dovetails nicely with Genodes quota based
resource management as any process can grant subsets of its own
CPU-time and priorities to its child without knowing the global means of
CPU-time and priority.
The commit also adds a run script that enables an automated unit test of the
scheduler implementation.
fix#1225
To serve the needs of the coming CPU scheduler, the double list needs
additional methods such as 'to_tail' and 'insert_head'.
The commit also adds a run script that enables an automated unit test
of the list implementation.
ref #1225
Kernel tests are done by replacing the implementation of an otherwise
empty function 'Kernel::test' that gets called once at the primary CPU
as soon as all kernel initialization is done. To achieve this, the test
binary that implements 'Kernel::test' must be linked against the core
lib and must then replace the core binary when composing the boot image.
The latter can be done conveniently in a run script by setting the new
argument 'core_type' of the function 'build_boot_image' to the falue
'test'. If no kernel test is needed the argument does not have to be
given - it is set to 'core' by default which results in a "normal"
Genode image.
ref #1225
Previously, Idle_thread inherited from Thread which caused an extra
processor_pool.h and processor_pool.cc and also made class models for
processor and scheduling more complex. However, this inheritance makes
not much sense anyway as an idle context doesn't trigger most of the code
in Thread.
ref #1225
The memory barrier prevents the compiler from changing the program order
of memory accesses in such a way that accesses to the guarded resource
get outside the guarded stage. As cmpxchg() defines the start of the
guarded stage it also represents an effective memory barrier.
On x86, the architecture ensures to not reorder writes with older reads,
writes to memory with other writes (except in cases that are not
relevant for our locks), or read/write instructions with I/O
instructions, locked instructions, and serializing instructions.
However on ARM, the architectural memory model allows not only that
memory accesses take local effect in another order as their program
order but also that different observers (components that can access
memory like data-busses, TLBs and branch predictors) observe these
effects each in another order. Thus, a correct program order isn't
sufficient for a correct observation order. An additional architectural
preservation of the memory barrier is needed to achieve this.
Fixes#692
Invalidating all branch predictors before switching the PD
fixes instability problems on Panda and has not much effect
on the performance of other boards. However, we neither know why
this is a fix nor wether it fixes the real cause of the problem.
fix#1294
Previously, the timer was used to remember the state of the time slices.
This was sufficient before priorities entered the scene as a thread always
received a fresh time slice when he was scheduled away. However, with
priorities this isn't always the case. A thread can be preempted by another
thread due to a higher priority. In this case the low-priority thread must
remember how much time he has consumed from its current time slice because
the timer gets re-programmed. Otherwise, if we have high-priority threads
that block and unblock with high frequency, the head of the next lower
priority would start with a fresh time slice all the time and is never
superseded.
fix#1287
* When flushing the data and unified cache on ARM, clean and invalidate
instead of just cleaning the corresponding cache lines
* After zero-ing a freshly constructed dataspace in core, invalidate
corresponding cache lines from the instruction cache
After modifying mode transition for branch prediction tz_vmm wasn't
working anymore on hw_imx53_tz but the modifications had nothing to do
with the VM code. However, the amount of instructions in the MT before the
VM exception-vector changed. So I tried stuffing the last working version with
NOPs and found that tz_vmm worked for some NOP amounts and for others not.
Thus, I increased the alignment of the VM exception-vector from 16 bytes to 32
bytes, é voila, its working with any amount of NOPs as well as with branch
prediction commits.
ref #474
Previously, we did the protection-domain switches without a transitional
translation table that contains only global mappings. This was fine as long
as the CPU did no speculative memory accesses. However, to enabling branch
prediction triggers such accesses. Thus, if we don't want to invalidate
predictors on every context switch, we need to switch more carefully.
ref #474
The build config for core is now provided through libraries to enable
implicit config composition through specifiers and thereby avoid
consideration of inappropriate targets.
fix#1199
A subject that inherits from Processor_client not necessarily has the need for
doing a processor-global TLB flush (e.g. VMs). At the other hand the Thread
class (as representation of the only source of TLB flushes) is already one of
the largest classes in base-hw because it provides all the syscall backends
and should therefore not accumulate other aspects without a functional reason.
Hence, I decided to move the aspect of synchronizing a TLB flush over all
processors to a dedicated class named Processor_domain_update.
Additionally a singleton of Processor_domain_update_list is used to enable
each processor to see all update-domain requests that are currently pending.
fix#1174
Commit 6a3368ee that refactored the mode transition assembler path, and
high-level entry point, fundamentally broke that part for the TrustZone VMs.
Instead of jumping to the appropriated address, the instruction value at that
point where used as target address.
Moreover, the TrustZone part of the mode transition page was not included into
the boundary check.
Ref #1182
On ARM it's relevant to not only distinguish between ordinary cached memory
and write-combined one, but also having non-cached memory too. To insert the
appropriated page table entries e.g.: in the base-hw kernel, we need to preserve
the information about the kind of memory from allocation until the pager
resolves a page fault. Therefore, this commit introduces a new Cache_attribute
type, and replaces the write_combined boolean with the new type where necessary.
Don't define assembler constants inside macros, thereby calling the
corresponding macros isn't needed anymore. To prevent having to much
constants included in files where they aren't needed, split macros.s
file into a generic mode_transition.s part, and globally used macros.s.
Fix#1180
Previously this was not done before Thread_base::start(..) in
base-hw as it was not needed to have a valid cap that early. However,
when changing the affinity of a thread we need the cap to be valid
before Thread_base::start(..).
fix#1151
By now the scheduling timer was only refreshed for a new scheduling timeout
when the choosen scheduling context has changed. But we want it to be refreshed
also when the scheduled context yields without an effect to the schedulers
choice (this is the case e.g. when the idle thread gets a scheduling timeout
or a thread yields without any competitor in its priority band).
ref #1151
Fixes an alignment problem introduced by commit "hw: map core on demand"
where physical address alignment wasn't checked anymore, when inserting
a section within the first-level table of ARM's short translation table
format.
Many thanks to Christian Prochaska for helping to debug the problem.
On ARM, when machine instructions get written into the data cache
(for example by a JIT compiler), one needs to make sure that the
instructions get written out to memory and read from memory into
the instruction cache before they get executed. This functionality
is usually provided by a kernel syscall and this patch adds a generic
interface for Genode applications to use it.
Fixes#1153.
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
