Messages in this thread | | | Subject | Re: [PATCH v5.1 27/34] KVM: SVM: Add support for booting APs in an SEV-ES guest | From | Tom Lendacky <> | Date | Thu, 7 Jan 2021 13:53:36 -0600 |
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On 1/7/21 12:13 PM, Paolo Bonzini wrote: > On 04/01/21 21:20, Tom Lendacky wrote: >> From: Tom Lendacky <thomas.lendacky@amd.com> >> >> Typically under KVM, an AP is booted using the INIT-SIPI-SIPI sequence, >> where the guest vCPU register state is updated and then the vCPU is VMRUN >> to begin execution of the AP. For an SEV-ES guest, this won't work because >> the guest register state is encrypted. >> >> Following the GHCB specification, the hypervisor must not alter the guest >> register state, so KVM must track an AP/vCPU boot. Should the guest want >> to park the AP, it must use the AP Reset Hold exit event in place of, for >> example, a HLT loop. >> >> First AP boot (first INIT-SIPI-SIPI sequence): >> Execute the AP (vCPU) as it was initialized and measured by the SEV-ES >> support. It is up to the guest to transfer control of the AP to the >> proper location. >> >> Subsequent AP boot: >> KVM will expect to receive an AP Reset Hold exit event indicating that >> the vCPU is being parked and will require an INIT-SIPI-SIPI sequence to >> awaken it. When the AP Reset Hold exit event is received, KVM will place >> the vCPU into a simulated HLT mode. Upon receiving the INIT-SIPI-SIPI >> sequence, KVM will make the vCPU runnable. It is again up to the guest >> to then transfer control of the AP to the proper location. >> >> To differentiate between an actual HLT and an AP Reset Hold, a new MP >> state is introduced, KVM_MP_STATE_AP_RESET_HOLD, which the vCPU is >> placed in upon receiving the AP Reset Hold exit event. Additionally, to >> communicate the AP Reset Hold exit event up to userspace (if needed), a >> new exit reason is introduced, KVM_EXIT_AP_RESET_HOLD. >> >> A new x86 ops function is introduced, vcpu_deliver_sipi_vector, in order >> to accomplish AP booting. For VMX, vcpu_deliver_sipi_vector is set to the >> original SIPI delivery function, kvm_vcpu_deliver_sipi_vector(). SVM adds >> a new function that, for non SEV-ES guests, invokes the original SIPI >> delivery function, kvm_vcpu_deliver_sipi_vector(), but for SEV-ES guests, >> implements the logic above. >> >> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> > > Queued, thanks.
Thanks, Paolo!
Tom
> > Paolo >
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