Re: [PATCH v5] KVM x86/xen: add an override for PVCLOCK_TSC_STABLE_BIT

[David Woodhouse]

On Thu, 2023-11-02 at 16:21 +0000, Paul Durrant wrote:
> From: Paul Durrant <pdurrant@xxxxxxxxxx>
> 
> Unless explicitly told to do so (by passing 'clocksource=tsc' and
> 'tsc=stable:socket', and then jumping through some hoops concerning
> potential CPU hotplug) Xen will never use TSC as its clocksource.
> Hence, by default, a Xen guest will not see PVCLOCK_TSC_STABLE_BIT set
> in either the primary or secondary pvclock memory areas. This has
> led to bugs in some guest kernels which only become evident if
> PVCLOCK_TSC_STABLE_BIT *is* set in the pvclocks. Hence, to support
> such guests, give the VMM a new Xen HVM config flag to tell KVM to
> forcibly clear the bit in the Xen pvclocks.
> 
> Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>

Reviewed-by: David Woodhouse <dwmw@xxxxxxxxxxxx>

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