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Hello,



We are discussing an API change regarding the boot timer feature in Firecracker.



The boot timer device supports logging the boot time of the guest since InstanceStart command. In the past, this was handled using PIO for x86_64 and MMIO for aarch64. In order to unify the code in a generic mechanism, we came up with a MMIO boot timer 'device'. The implementation for x86_64 involved changing PIO writes to 0x03f0 to MMIO writes to 0xd0000000. For aarch64 the mechanism did not change.


This boot time functionality is used only during testing, therefore we decided to load the device only when specified, instead of activating it by default. A dedicated --boot-timer parameter would be added to the cmdline options in order to request the boot timer feature.


This is an API breaking change for those who use the boot timer. Please let us know about any concerns you may have around it.



Thank you,

Luminita on behalf of the Firecracker Team






Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.
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