The 'Thread_base' class is constructed differently in some special cases
like the main thread or a thread that use a distinct CPU session. The
official API, however, should be clean from such artifacts. Hence, I
separated the official constructor from the other cases.
VirtualBox can receive absolute or relative mouse motion events from the
'Input' service and the VM can support either or both of them. With this
patch, more of the possible combinations are handled.
Fixes#1470
There were two bugs. First, the caller of Kernel::await_signal wasn't
re-activated for scheduling. Second, the caller did not memorize that he
doesn't wait on a receiver anymore which had bad side effects on further
signal handling.
Fix#1459
The port uses the Cortex-A9 private timer for the kernel and an EPIT as
user timer. It was successfully tested on the Wandboard Quad and the CuBox-i
with the signal test. It lacks L2-cache and Trustzone support by now.
Thanks to Praveen Srinivas (IIT Madras, India) and Nikolay Golikov (Ksys Labs
LLC, Russia). This work is partially based on their contributions.
Fix#1467
Do not mask edge-triggered interrupts to avoid losing them while masked,
see Intel 82093AA I/O Advanced Programmable Interrupt Controller
(IOAPIC) specification, section 3.4.2, "Interrupt Mask":
"When this bit is 1, the interrupt signal is masked. Edge-sensitive
interrupts signaled on a masked interrupt pin are ignored (i.e., not
delivered or held pending)"
Or to quote Linus Torvalds on the subject:
"Now, edge-triggered interrupts are a _lot_ harder to mask, because the
Intel APIC is an unbelievable piece of sh*t, and has the edge-detect
logic _before_ the mask logic, so if a edge happens _while_ the device
is masked, you'll never ever see the edge ever again (unmasking will not
cause a new edge, so you simply lost the interrupt)."
So when you "mask" an edge-triggered IRQ, you can't really mask it at
all, because if you did that, you'd lose it forever if the IRQ comes in
while you masked it. Instead, we're supposed to leave it active, and set
a flag, and IF the IRQ comes in, we just remember it, and mask it at
that point instead, and then on unmasking, we have to replay it by
sending a self-IPI." [1]
[1] - http://yarchive.net/comp/linux/edge_triggered_interrupts.html
Ref #1448
In order to match the I/O APIC configuration, a request for user timer
IRQ 0 is remapped to vector 50 (Board::TIMER_VECTOR_USER), all other
requests are transposed by adding the vector offset 48
(Board::VECTOR_REMAP_BASE).
On base-hw/x86_64 the quota of the signal session is not sufficient due to
the large size of the Signal_session_component. Increasing the quota to
16K avoids signal-context resource exhaustion messages as emmitted by the
run/launcher scenario:
...
Quota exceeded! amount=4096, size=4096, consumed=4096
failed to allocate signal-context resources
upgrading quota donation for signal session
C++ runtime: Genode::Parent::Quota_exceeded
void* abort(): abort called
...
Note: This change increases the quota for all kernels even though it is
strictly only required for base-hw/x86_64.
* Enable the use of the FXSAVE and FXRSTOR instructions, see Intel SDM
Vol. 3C, section 2.5.
* The state of the x87 floating point unit (FPU) is loaded and saved on
demand.
* Make the cr0 control register accessible in the Cpu class. This is in
preparation of the upcoming FPU management.
* Access to the FPU is disabled by setting the Task Switch flag in the cr0
register.
* Access to the FPU is enabled by clearing the Task Switch flag in the cr0
register.
* Implement FPU initialization
* Add is_fpu_enabled helper function
* Add pointer to CPU lazy state to CPU class
* Init FPU when finishing kernel initialization
* Add function to retry FPU instruction:
Similar to the ARM mechanism to retry undefined instructions, implement a
function for retrying an FPU instruction. If a floating-point instruction
causes an #NM exception due to the FPU being disabled, it can be retried
after the correct FPU state is restored, saving the current state and
enabling the FPU in the process.
* Disable FPU when switching to different user context:
This enables lazy save/restore of the FPU since trying to execute a
floating point instruction when the FPU is disabled will cause a #NM
exception.
* Declare constant for #NM exception
* Retry FPU instruction on #NM exception
* Assure alignment of FXSAVE area:
The FXSAVE area is 512-byte memory region that must be 16-byte aligned. As
it turns out the alignment attribute is not honored in all cases so add a
workaround to assure the alignment constraint is met by manually rounding
the start of the FXSAVE area to the next 16-byte boundary if necessary.
The LAPIC timer is programmed in one-shot mode with vector 32
(Board::TIMER_VECTOR_KERNEL). The timer frequency is measured using PIT
channel 2 as reference (50ms delay).
Disable PIT timer channel 0 since BIOS programs it to fire periodically.
This avoids potential spurious timer interrupts.
The implementation initializes the Local APIC (LAPIC) of CPU 0 in xapic
mode (mmio register access) and uses the I/O APIC to remap, mask and
unmask hardware IRQs. The remapping offset of IRQs is 48.
Also initialize the legacy PIC and mask all interrupts in order to
disable it.
For more information about LAPIC and I/O APIC see Intel SDM Vol. 3A,
chapter 10 and the Intel 82093AA I/O Advanced Programmable Interrupt
Controller (IOAPIC) specification
Set bit 9 in the RFLAGS register of user CPU context to enable
interrupts on kernel- to usermode switch.
Make the local APIC accessible via its MMIO region by adding a 2 MB
large page mapping at 0xfee00000 with memory type UC.
Note: The mapping is added to the initial page tables to make the APIC
usable prior to the activation of core's page tables, e.g. in the
constructor of the timer class.
The location in memory is arbitrary but we use the same address as the
ARM architecture. Adjust references to virtual addresses in the mode
transition pages to cope with 64-bit values.
