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    SubjectRE: [PATCH v5 05/16] clocksource/hyperv: use MSR-based access if running as root
    Date
    From: Wei Liu <wei.liu@kernel.org> Sent: Wednesday, January 20, 2021 4:01 AM
    >
    > When Linux runs as the root partition, the setup required for TSC page
    > is different. Luckily Linux also has access to the MSR based
    > clocksource. We can just disable the TSC page clocksource if Linux is
    > the root partition.
    >
    > Signed-off-by: Wei Liu <wei.liu@kernel.org>
    > Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
    > ---
    > drivers/clocksource/hyperv_timer.c | 3 +++
    > 1 file changed, 3 insertions(+)
    >
    > diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
    > index ba04cb381cd3..269a691bd2c4 100644
    > --- a/drivers/clocksource/hyperv_timer.c
    > +++ b/drivers/clocksource/hyperv_timer.c
    > @@ -426,6 +426,9 @@ static bool __init hv_init_tsc_clocksource(void)
    > if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
    > return false;
    >
    > + if (hv_root_partition)
    > + return false;
    > +
    > hv_read_reference_counter = read_hv_clock_tsc;
    > phys_addr = virt_to_phys(hv_get_tsc_page());
    >
    > --
    > 2.20.1

    Reviewed-by: Michael Kelley <mikelley@microsoft.com>

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