Hi Boqun Feng, On 24/01/2020 06:32, Boqun Feng wrote: > Hi Vincenzo, > [...] >> >> I had a look to your patches and overall, I could not understand why we can't >> use the arch_timer to do the same things you are doing with the one you >> introduced in this series. What confuses me is that KVM works just fine with the >> arch_timer which was designed with virtualization in mind. Why do we need >> another one? Could you please explain? >> > > Please note that the guest VM on Hyper-V for ARM64 doesn't use > arch_timer as the clocksource. See: > > https://lore.kernel.org/linux-arm-kernel/1570129355-16005-7-git-send-email-mikelley@xxxxxxxxxxxxx/ > > , ACPI_SIG_GTDT is used for setting up Hyper-V synthetic clocksource > and other initialization work. > I had a look a look at it and my question stands, why do we need another timer on arm64? > So just to be clear, your suggestion is > > 1) Hyper-V guest on ARM64 should use arch_timer as clocksource and vDSO > will just work. > > or > > 2) Even though arch_timer is not used as the clocksource, we can still > use it for vDSO. > > ? > Option #1 would be the preferred solution, unless there is a good reason against. > Regards, > Boqun > -- Regards, Vincenzo
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