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include vmm.inc mov ecx, Flags ; flags for servicing interrupts VMMcall Begin_Critical_Section |
The Begin_Critical_Section service causes the current virtual machine to enter a critical section. Only one virtual machine can own the critical section at a time. If a virtual machine calls this service while another virtual machine owns the critical section, the calling virtual machine will block until the critical section is released.
Flags
Specifies actions to take when interrupts occur while the virtual machine is blocked waiting for the critical section. This parameter can be a combination of the following values:
| Value | Meaning |
| Block_Enable_Ints | Service interrupts in the virtual machine even if the virtual machine does not currently have interrupts enabled. This forces interrupts to be enabled. This value is only relevant if either Block_Svc_Ints or Block_Svc_If_Ints_Locked is set. |
| Block_Svc_If_Ints_Locked | Service interrupts in the virtual machine even if the virtual machine is blocked, and the VMStat_V86IntsLocked flag is set. |
| Block_Svc_Ints | Service interrupts in the virtual machine even if the virtual machine is blocked. |
The Block_Poll value is reserved and must not be used with this service.
This service has no return value.
The system maintains a count of claims for critical sections and releases the critical section only when an equal number of Begin_Critical_Section and End_Critical_Section services have been called.
When the critical section is first claimed, the system boosts the execution priority of the current virtual machine by the Critical_Section_Boost value (as described for the Adjust_Exec_Priority service). While a virtual machine is in a critical section, the system will switch to another task only if the virtual machine blocks on a semaphore or the other task has a time-critical operation, such as simulating hardware interrupts.
Flags