On 7/27/2015 11:45 AM, Andy Lutomirski wrote:
With PARAVIRT=y it never #GPs: .read_msr = native_read_msr_safe, .write_msr = native_write_msr_safe, I don't remember if it's this way on bare-metal too.Oh, whoops, I missed the "_safe". IMO that's just a bug, and I guess KVM relies on it?
btw it's a common misperception that _safe is actually safe;-) they're still highly dangerous, just they won't fault on the linux side
ISTM the host should be fixed so that a non-PARAVIRT guest won't crash when using perf (if it indeed currently crashes) and/or the perf code should be fixed to work without this bug^Wfeature. Then KVM_GUEST kernels could be de-bloated by dropping PARAVIRT. Hi Arjan- A quick and dirty measurement suggests that this would save 2-3 ms when booting a KVM_GUEST=y kernel under KVM by turning apply_paravirt into a noop.
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