On Mon, 2018-02-19 at 14:10 +0100, Paolo Bonzini wrote: > > Hardware seems like a reasonable place to get the default value (cf. > > the VMX capability MSRs). > > There are some differences: > > - a zero value for ARCH_CAPABILITIES should be safe, while a zero value > for VMX capabilities doesn't really make sense. On the contrary, a > nonzero value for ARCH_CAPABILITIES is not safe across live migration.
Any VMM which is going to support live migration surely needs to pay at least a small amount of attention to the features it exposes? Exposing the ARCH_CAPABILITIES CPUID bit without actually looking at the contents of the associated MSR which that bit advertises would be... a little strange, would it not? I don't see why we care so much about the *default* value, in that context.
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