On 01/03/2021 02:15, Michael Kelley wrote: > On x86/x64, the TSC clocksource is available in a Hyper-V VM only if > Hyper-V provides the TSC_INVARIANT flag. The rating on the Hyper-V > Reference TSC page clocksource is currently set so that it will not > override the TSC clocksource in this case. Alternatively, if the TSC > clocksource is not available, then the Hyper-V clocksource is used. > > But on ARM64, the Hyper-V Reference TSC page clocksource should > override the ARM arch counter, since the Hyper-V clocksource provides > scaling and offsetting during live migrations that is not provided > for the ARM arch counter. > > To get the needed behavior for both x86/x64 and ARM64, tweak the > logic by defaulting the Hyper-V Reference TSC page clocksource > rating to a large value that will always override. If the Hyper-V > TSC_INVARIANT flag is set, then reduce the rating so that it will not > override the TSC. > > While the logic for getting there is slightly different, the net > result in the normal cases is no functional change. > > Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx> Acked-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> [ ... ] -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
