When all vCPU threads on one pCPU are put to sleep (e.g., when all
guests execute HLT), hv would schedule to idle thread. Currently the
idle thread executes PAUSE which does not enter any c-state and consumes
a lot of power. This patch is to support HLT in the idle thread.
When we switch to HLT, we have to make sure events that would wake a
vCPU must also be able to wake the pCPU. Those events are either
generated by local interrupt or issued by other pCPUs followed by an
ipi kick.
Each of them have an interrupt involved, so they are also able to wake
the halted pCPU. Except when the pCPU has just scheduled to idle thread
but not yet halted, interrupts could be missed.
sleep-------schedule to idle------IRQ ON---HLT--(kick missed)
^
wake---kick|
This areas should be protected. This is done by a safe halt
mechanism leveraging STI instruction’s delay effect (same as Linux).
vCPUs with lapic_pt or hv with CONFIG_KEEP_IRQ_DISABLED=y does not allow
interrupts in root mode, so they could never wake from HLT (INIT kick
does not wake HLT in root mode either). They should continue using PAUSE
in idle.
Tracked-On: #8507
Signed-off-by: Wu Zhou <wu.zhou@intel.com>
Reviewed-by: Junjie Mao <junjie.mao@intel.com>
Modified the copyright year range in code, and corrected "int32_tel"
into "Intel" in two "hypervisor/include/debug/profiling.h" and
"hypervisor/include/debug/profiling_internal.h".
Tracked-On: #7559
Signed-off-by: Ziheng Li <ziheng.li@intel.com>
Commit d575edf79a changes the internal
implementation of wait_event and signal_event to use a counter instead
of a boolean value.
The background was:
ACRN utilizes vcpu_make_request and signal_event pair to shoot down
other vcpus and let them wait for signals. vcpu_make_request eventually
leads to target vcpu calling wait_event.
However vcpu_make_request/signal_event pair was not thread-safe,
and concurrent calls of this pair of API could lead to problems.
One such example is the concurrent wbinvd emulation, where vcpus may
concurrently issue vcpu_make_request/signal_event to synchronize wbinvd
emulation.
d575edf commit uses a counter in internal implementation of
wait_event/signal_event to avoid data races.
However by using a counter, the wait/signal pair now carries semantics of
semaphores instead of events. Semaphores require caller to carefully
plan their calls instead of multiply signaling any number of times to the same
event, which deviates from the original "event" semantics.
This patch changes the API implementation back to boolean-based, and
re-resolve the issue of concurrent wbinvd in next patch.
This also partially reverts commit 10963b04d1,
which was introduced because of the d575edf.
Tracked-On: #7887
Signed-off-by: Yifan Liu <yifan1.liu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
Many of the license and Intel copyright headers include the "All rights
reserved" string. It is not relevant in the context of the BSD-3-Clause
license that the code is released under. This patch removes those strings
throughout the code (hypervisor, devicemodel and misc).
Tracked-On: #7254
Signed-off-by: Geoffroy Van Cutsem <geoffroy.vancutsem@intel.com>
Currently the sched event handling may encounter data race problem, and
as a result some vcpus might be stalled forever.
One example can be wbinvd handling where more than 1 vcpus are doing
wbinvd concurrently. The following is a possible execution of 3 vcpus:
-------
0 1 2
req [Note: 0]
req bit0 set [Note: 1]
IPI -> 0
req bit2 set
IPI -> 2
VMExit
req bit2 cleared
wait
vcpu2 descheduled
VMExit
req bit0 cleared
wait
vcpu0 descheduled
signal 0
event0->set=true
wake 0
signal 2
event2->set=true [Note: 3]
wake 2
vcpu2 scheduled
event2->set=false
resume
req
req bit0 set
IPI -> 0
req bit1 set
IPI -> 1
(doesn't matter)
vcpu0 scheduled [Note: 4]
signal 0
event0->set=true
(no wake) [Note: 2]
event0->set=false (the rest doesn't matter)
resume
Any VMExit
req bit0 cleared
wait
idle running
(blocked forever)
Notes:
0: req: vcpu_make_request(vcpu, ACRN_REQUEST_WAIT_WBINVD).
1: req bit: Bit in pending_req_bits. Bit0 stands for bit for vcpu0.
2: In function signal_event, At this time the event->waiting_thread
is not NULL, so wake_thread will not execute
3: eventX: struct sched_event of vcpuX.
4: In function wait_event, the lock does not strictly cover the execution between
schedule() and event->set=false, so other threads may kick in.
-----
As shown in above example, before the last random VMExit, vcpu0 ended up
with request bit set but event->set==false, so blocked forever.
This patch proposes to change event->set from a boolean variable to an
integer. The semantic is very similar to a semaphore. The wait_event
will add 1 to this value, and block when this value is > 0, whereas signal_event
will decrease this value by 1.
It may happen that this value was decreased to a negative number but that
is OK. As long as the wait_event and signal_event are paired and
program order is observed (that is, wait_event always happens-before signal_event
on a single vcpu), this value will eventually be 0.
Tracked-On: #6405
Signed-off-by: Yifan Liu <yifan1.liu@intel.com>
Instead of "#include <x86/foo.h>", use "#include <asm/foo.h>".
In other words, we are adopting the same practice in Linux kernel.
Tracked-On: #5920
Signed-off-by: Liang Yi <yi.liang@intel.com>
Reviewed-by: Jason Chen CJ <jason.cj.chen@intel.com>
Requires explicit arch path name in the include directive.
The config scripts was also updated to reflect this change.
Tracked-On: #5825
Signed-off-by: Peter Fang <peter.fang@intel.com>
Reviewed-by: Jason Chen CJ <jason.cj.chen@intel.com>
On UEFI UP2 board, APs might execute HLT before SOS kernel INIT them.
After SOS kernel take over and will re-init the APs directly. The flows
from HV perspective is like:
HLT trap:
wait_event(VCPU_EVENT_VIRTUAL_INTERRUPT) -> sleep_thread
SOS kernel INIT, SIPI APs:
pause_vcpu(ZOMBIE) -> sleep_thread
-> reset_vcpu
-> launch_vcpu -> wake_vcpu
However, the last wake_vcpu will fail because the cpu event
VCPU_EVENT_VIRTUAL_INTERRUPT had not got signaled.
This patch will reset all vcpu events in reset_vcpu. If the thread was
previously waiting for a event, its waiting status will be cleared and
launch_vcpu will wake it to running.
Tracked-On: #4402
Signed-off-by: Shuo A Liu <shuo.a.liu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
This simple event implemention can only support exclusive waiting
at same time. It mainly used by thread who want to wait for special event
happens.
Thread A who want to wait for some events calls
wait_event(struct sched_event *);
Thread B who can give the event signal calls
signal_event(struct sched_event *);
Tracked-On: #4329
Signed-off-by: Shuo A Liu <shuo.a.liu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
Wu Zhou