Re: [PATCH 6/6] KVM: nVMX: support RDRAND and RDSEED exiting

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From	Paolo Bonzini <pbonzini@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 6/6] KVM: nVMX: support RDRAND and RDSEED exiting
Date	Tue, 14 Mar 2017 11:00:02 +0100
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On 13/03/2017 19:27, Jim Mattson wrote:
> I would expect that any reasonable CPU will support "RDRAND exiting"
> iff it supports RDRAND (i.e. CPUID.01H:ECX.RDRAND[bit 30]).
> Similarly, any reasonable CPU will support "RDSEED exiting" iff it
> supports RDSEED (i.e. CPUID.(EAX=07H, ECX=0H):EBX.RDSEED[bit 18]).
> 
> Shouldn't there be some code in vmx_cpuid_update to adjust the
> vmx->nested.nested_vmx_secondary_ctls_high bits for "RDRAND exiting"
> and "RDSEED exiting," as there already is for "enable RDTSCP"?

Enable RDTSCP is a bit different in that the instruction itself is
disabled rather than the VMEXIT, still it would probably be a good idea.

One thing to be careful about is any conflicts with David Matlack's work
to customize the MSRs for processor models, since there's no prescribed
ordering of KVM_SET_CPUID2 and KVM_SET_MSR.  Maybe
nested_vmx_setup_ctls_msrs can save the "default" nested_*_ctls_*; then
vmx_restore_control_msr can refer to those in order to check the written
value against the supported bits.

Paolo

Thread

[PATCH 0/6] KVM: nVMX: nested EPT improvements and A/D bits, RDRAND and RDSEED exits Paolo Bonzini <pbonzini@redhat.com> - 2017-03-08 19:20 +0100
  [PATCH 6/6] KVM: nVMX: support RDRAND and RDSEED exiting Paolo Bonzini <pbonzini@redhat.com> - 2017-03-08 19:20 +0100
    Re: [PATCH 6/6] KVM: nVMX: support RDRAND and RDSEED exiting Jim Mattson <jmattson@google.com> - 2017-03-13 19:30 +0100
      Re: [PATCH 6/6] KVM: nVMX: support RDRAND and RDSEED exiting Paolo Bonzini <pbonzini@redhat.com> - 2017-03-14 11:00 +0100
  [PATCH 2/6] KVM: VMX: cleanup check for invalid EPT violation Paolo Bonzini <pbonzini@redhat.com> - 2017-03-08 19:40 +0100
    Re: [PATCH 2/6] KVM: VMX: cleanup check for invalid EPT violation David Hildenbrand <david@redhat.com> - 2017-03-09 12:00 +0100
      Re: [PATCH 2/6] KVM: VMX: cleanup check for invalid EPT violation David Hildenbrand <david@redhat.com> - 2017-03-09 12:00 +0100
  [PATCH 1/6] KVM: nVMX: we support 1GB EPT pages Paolo Bonzini <pbonzini@redhat.com> - 2017-03-08 19:40 +0100
    Re: [PATCH 1/6] KVM: nVMX: we support 1GB EPT pages David Hildenbrand <david@redhat.com> - 2017-03-09 11:40 +0100
  [PATCH 4/6] kvm: nVMX: support EPT accessed/dirty bits Paolo Bonzini <pbonzini@redhat.com> - 2017-03-08 19:40 +0100
  [PATCH 3/6] kvm: x86: MMU support for EPT accessed/dirty bits Paolo Bonzini <pbonzini@redhat.com> - 2017-03-08 20:10 +0100

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