[Xen-devel] Xen Guest Timer (ARM) question

[embeddev student <embed.dev.student@xxxxxxxxx>]

Hello Xen Team,

I am trying to understand the Timer implementation for a Guest. After going through the code I have a few trivial questions,Â

a) As per ARM documentation There are 3 timers

i) Physical Timer

ii) Virtual Timer

iii) Hypervisor TimerÂ

As per my understanding the hypervisor timer is for Xen and Virtual Timer is for Domain. I am not able to find the need for a physical timer in a Xen system.

Q1. Why is guest not given only a virtual timer, What is the need for Âthe guest to have a physical timer as well ?

Q2. In virt_timer_save set_timer is called. If vcpu is going in a suspended state what is the requirement of a timer being set ?

Thanks and Best Regards

embedded dev student

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