Re: kvm: RDTSCP on AMD

From	Paolo Bonzini <pbonzini@redhat.com>
Newsgroups	linux.kernel
Subject	Re: kvm: RDTSCP on AMD
Date	2016-07-06 23:30 +0200
Message-ID	<rS2ym-64W-17@gated-at.bofh.it> (permalink)
References	<rRUr8-OO-17@gated-at.bofh.it> <rRUKu-1aw-11@gated-at.bofh.it> <rRYXL-3I6-3@gated-at.bofh.it>
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On 06/07/2016 19:34, Eduardo Habkost wrote:
>> > Nothing is needed in the kernel actually.  You can skip the intercept
>> > by running the guest with MSR_TSC_AUX set to the guest's expected value.
>> >  Which KVM does, except that it's botched so I need to apply the
>> > patch in https://lkml.org/lkml/2016/4/13/802.
> Do you mean -cpu Opteron_G*,+rdtscp will be buggy on Linux v4.5?
> (v4.5 reports rdtscp as supported in GET_SUPPORTED_CPUID)
> 
> Can we do something to make QEMU detect the buggy kernel before
> allowing rdtscp to be enabled, or should we just tell people to
> upgrade their kernel?

We usually just tell people to use the latest stable kernel.

Adding new CPU models is not a big deal, in fact it's almost easier than
getting compat properties right. :)

Paolo

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Thread

kvm: RDTSCP on AMD Borislav Petkov <bp@alien8.de> - 2016-07-06 14:50 +0200
  Re: kvm: RDTSCP on AMD Paolo Bonzini <pbonzini@redhat.com> - 2016-07-06 15:10 +0200
    Re: kvm: RDTSCP on AMD Eduardo Habkost <ehabkost@redhat.com> - 2016-07-06 19:40 +0200
      Re: kvm: RDTSCP on AMD Paolo Bonzini <pbonzini@redhat.com> - 2016-07-06 23:30 +0200

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