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kvm: i8254: Fix conversion of in-kernel to userspace state
Due to a offset between the clock used to generate the in-kernel count_load_time (CLOCK_MONOTONIC) and the clock used for processing this in userspace (vm_clock), reading back the output of PIT channel 2 via port 0x61 was broken. One use cases that suffered from it was the CPU frequency calibration of SeaBIOS, which also affected IDE/AHCI timeouts. This fixes it by calibrating the offset between both clocks on kvm_pit_get and adjusting the kernel value before saving it in the userspace state. As the calibration only works while the vm_clock is running, we cache the in-kernel state across stopped phases. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Avi Kivity <avi@redhat.com>
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