Re: [Xen-devel] [PATCH v2 6/9] x86/vmx: Pass an MSR value into vmx_msr_add()

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: Saturday, June 9, 2018 2:49 AM
> 
> The main purpose of this change is to allow us to set a specific MSR value,
> without needing to know whether there is already a load/save list slot for it.
> 
> Previously, callers wanting this property needed to call both
> vmx_add_*_msr()
> and vmx_write_*_msr() to cover both cases, and there are no callers which
> want
> the old behaviour of being a no-op if an entry already existed for the MSR.
> 
> As a result of this API improvement, the default value for guest MSRs need
> not
> be 0, and the default for host MSRs need not be passed via hardware
> register.
> In practice, this cleans up the VPMU allocation logic, and avoids an MSR
> read
> as part of vcpu construction.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
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