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hv: add bitmap_clear_lock of split-lock after completing emulation

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Suppose the current vcpu is 0, the other vcpus (1, 2, 3) may wait on the
"get_split_lock", the current vcpu need clear the ACRN_REQUEST_SPLIT_LOCK
explicitly here after finishing the emulation. Otherwise, it make cause
dead lock. for example:
	1. Once vcpu 0 "put_split_lock", let's say vcpu 1 will "get_split_lock".
	2. vcpu 1 call "vcpu_make_request" to pause vcpu 0, 2, 3.
	3. vcpu 1's VCPU_EVENT_SPLIT_LOCK is still not cleared because
	   the vcpu 0 called "vcpu_make_request" ever.
	4. All vcpus will wait for VCPU_EVENT_SPLIT_LOCK in acrn_handle_pending_request.
We should avoid this dead lock case.

Please note: this patch is only for release 2.5 test.

Tracked-On: #6051
Signed-off-by: Jie Deng <jie.deng@intel.com>
This commit is contained in:
Jie Deng 2021-03-11 22:34:03 +08:00 committed by wenlingz
parent 070385c4f6
commit dba49b38df
1 changed files with 13 additions and 0 deletions
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13
hypervisor/arch/x86/guest/splitlock.c
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@ -49,6 +49,19 @@ void vcpu_complete_splitlock_emulation(struct acrn_vcpu *cur_vcpu)
if (cur_vcpu->vm->hw.created_vcpus > 1U) {
foreach_vcpu(i, cur_vcpu->vm, other) {
if (other != cur_vcpu) {
/*
* Suppose the current vcpu is 0, the other vcpus (1, 2, 3) may wait on the
* "get_vm_lock", the current vcpu need clear the ACRN_REQUEST_SPLIT_LOCK
* explicitly here after finishing the emulation. Otherwise, it make cause
* dead lock. for example:
* 1. Once vcpu 0 "put_vm_lock", let's say vcpu 1 will "get_vm_lock".
* 2. vcpu 1 call "vcpu_make_request" to pause vcpu 0, 2, 3.
* 3. vcpu 1's VCPU_EVENT_SPLIT_LOCK is still not cleared because
* the vcpu 0 called "vcpu_make_request" ever.
* 4. All vcpus will wait for VCPU_EVENT_SPLIT_LOCK in acrn_handle_pending_request.
* We should avoid this dead lock case.
*/
bitmap_clear_lock(ACRN_REQUEST_SPLIT_LOCK, &other->arch.pending_req);
signal_event(&other->events[VCPU_EVENT_SPLIT_LOCK]);
}
}