| Message ID | 20210902181751.252227-3-pgonda@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add AMD SEV and SEV-ES intra host migration support | expand |
On Thu, Sep 02, 2021, Peter Gonda wrote: > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 8db666a362d4..fac21a82e4de 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -1545,6 +1545,59 @@ static void migrate_info_from(struct kvm_sev_info *dst, > list_replace_init(&src->regions_list, &dst->regions_list); > } > > +static int migrate_vmsa_from(struct kvm *dst, struct kvm *src) > +{ > + int i, num_vcpus; > + struct kvm_vcpu *dst_vcpu, *src_vcpu; > + struct vcpu_svm *dst_svm, *src_svm; > + > + num_vcpus = atomic_read(&dst->online_vcpus); > + if (num_vcpus != atomic_read(&src->online_vcpus)) { > + pr_warn_ratelimited( > + "Source and target VMs must have same number of vCPUs.\n"); Same comments about not logging the why. > + return -EINVAL; > + } > + > + for (i = 0; i < num_vcpus; ++i) > + src_vcpu = src->vcpus[i]; This can be: kvm_for_each_vcpu(i, src_vcpu, src) { if (!src_vcpu->arch.guest_state_protected) return -EINVAL; } > + if (!src_vcpu->arch.guest_state_protected) { > + pr_warn_ratelimited( > + "Source ES VM vCPUs must have protected state.\n"); > + return -EINVAL; > + } > + } > + > + for (i = 0; i < num_vcpus; ++i) { And again here, kvm_for_each_vcpu(i, src_vcpu, src) { src_svm = to_svm(src_vcpu); > + src_vcpu = src->vcpus[i]; > + src_svm = to_svm(src_vcpu); > + dst_vcpu = dst->vcpus[i]; Probably a good idea to use kvm_get_vcpu(), even though dst->lock is held. If nothing else, using kvm_get_vcpu() may save some merge pain as there's a proposal to switch vcpus to an xarray. > + dst_svm = to_svm(dst_vcpu); > + > + /* > + * Copy VMSA and GHCB fields from the source to the destination. > + * Clear them on the source to prevent the VM running and As brought up in the prior patch, clearing the fields might ensure future KVM_RUNs fail, but it doesn't prevent the VM from running _now_. And with vcpu->mutext held, I think a more appropriate comment would be: /* * Transfer VMSA and GHCB state to the destination. Nullify and * clear source fields as appropriate, the state now belongs to * the destination. */ > + * changing the state of the VMSA/GHCB unexpectedly. > + */ > + dst_vcpu->vcpu_id = src_vcpu->vcpu_id; > + dst_svm->vmsa = src_svm->vmsa; > + src_svm->vmsa = NULL; > + dst_svm->ghcb = src_svm->ghcb; > + src_svm->ghcb = NULL; > + dst_svm->vmcb->control.ghcb_gpa = > + src_svm->vmcb->control.ghcb_gpa; Let this poke out, an 83 char line isn't the end of the world, and not having the interrupt makes the code more readable overall. > + src_svm->vmcb->control.ghcb_gpa = 0; Nit, '0' isn't an invalid GPA. The reset value would be more appropriate, though I would just leave this alone. > + dst_svm->ghcb_sa = src_svm->ghcb_sa; > + src_svm->ghcb_sa = NULL; > + dst_svm->ghcb_sa_len = src_svm->ghcb_sa_len; > + src_svm->ghcb_sa_len = 0; > + dst_svm->ghcb_sa_sync = src_svm->ghcb_sa_sync; > + src_svm->ghcb_sa_sync = false; > + dst_svm->ghcb_sa_free = src_svm->ghcb_sa_free; > + src_svm->ghcb_sa_free = false; > + } > + return 0; > +}
On Fri, Sep 10, 2021, Sean Christopherson wrote: > On Thu, Sep 02, 2021, Peter Gonda wrote: > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > > index 8db666a362d4..fac21a82e4de 100644 > > --- a/arch/x86/kvm/svm/sev.c > > +++ b/arch/x86/kvm/svm/sev.c > > @@ -1545,6 +1545,59 @@ static void migrate_info_from(struct kvm_sev_info *dst, > > list_replace_init(&src->regions_list, &dst->regions_list); > > } > > > > +static int migrate_vmsa_from(struct kvm *dst, struct kvm *src) Better to call this sev_es_migrate_from()... > > +{ > > + int i, num_vcpus; > > + struct kvm_vcpu *dst_vcpu, *src_vcpu; > > + struct vcpu_svm *dst_svm, *src_svm; > > + ...because this should also clear kvm->es_active. KVM_SEV_INIT isn't problematic (as currently written) because the common sev_guest_init() explicitly writes es_active, but I think a clever userspace could get an SEV ASID into an "ES" guest via KVM_CAP_VM_COPY_ENC_CONTEXT_FROM, which requires its dst to be !SEV and thus doesn't touch es_active. Huh, that's a bug, svm_vm_copy_asid_from() should explicitly disallow copying the ASID from an SEV-ES guest. I'll send a patch for that. Last thought, it's probably worth renaming migrate_info_from() to sev_migrate_from() to pair with sev_es_migrate_from().
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 8db666a362d4..fac21a82e4de 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -1545,6 +1545,59 @@ static void migrate_info_from(struct kvm_sev_info *dst, list_replace_init(&src->regions_list, &dst->regions_list); } +static int migrate_vmsa_from(struct kvm *dst, struct kvm *src) +{ + int i, num_vcpus; + struct kvm_vcpu *dst_vcpu, *src_vcpu; + struct vcpu_svm *dst_svm, *src_svm; + + num_vcpus = atomic_read(&dst->online_vcpus); + if (num_vcpus != atomic_read(&src->online_vcpus)) { + pr_warn_ratelimited( + "Source and target VMs must have same number of vCPUs.\n"); + return -EINVAL; + } + + for (i = 0; i < num_vcpus; ++i) { + src_vcpu = src->vcpus[i]; + if (!src_vcpu->arch.guest_state_protected) { + pr_warn_ratelimited( + "Source ES VM vCPUs must have protected state.\n"); + return -EINVAL; + } + } + + for (i = 0; i < num_vcpus; ++i) { + src_vcpu = src->vcpus[i]; + src_svm = to_svm(src_vcpu); + dst_vcpu = dst->vcpus[i]; + dst_svm = to_svm(dst_vcpu); + + /* + * Copy VMSA and GHCB fields from the source to the destination. + * Clear them on the source to prevent the VM running and + * changing the state of the VMSA/GHCB unexpectedly. + */ + dst_vcpu->vcpu_id = src_vcpu->vcpu_id; + dst_svm->vmsa = src_svm->vmsa; + src_svm->vmsa = NULL; + dst_svm->ghcb = src_svm->ghcb; + src_svm->ghcb = NULL; + dst_svm->vmcb->control.ghcb_gpa = + src_svm->vmcb->control.ghcb_gpa; + src_svm->vmcb->control.ghcb_gpa = 0; + dst_svm->ghcb_sa = src_svm->ghcb_sa; + src_svm->ghcb_sa = NULL; + dst_svm->ghcb_sa_len = src_svm->ghcb_sa_len; + src_svm->ghcb_sa_len = 0; + dst_svm->ghcb_sa_sync = src_svm->ghcb_sa_sync; + src_svm->ghcb_sa_sync = false; + dst_svm->ghcb_sa_free = src_svm->ghcb_sa_free; + src_svm->ghcb_sa_free = false; + } + return 0; +} + int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd) { struct kvm_sev_info *dst_sev = &to_kvm_svm(kvm)->sev_info; @@ -1556,7 +1609,7 @@ int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd) if (ret) return ret; - if (!sev_guest(kvm) || sev_es_guest(kvm)) { + if (!sev_guest(kvm)) { ret = -EINVAL; pr_warn_ratelimited("VM must be SEV enabled to migrate to.\n"); goto out_unlock; @@ -1582,13 +1635,18 @@ int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd) if (ret) goto out_fput; - if (!sev_guest(source_kvm) || sev_es_guest(source_kvm)) { + if (!sev_guest(source_kvm)) { ret = -EINVAL; pr_warn_ratelimited( "Source VM must be SEV enabled to migrate from.\n"); goto out_source; } + if (sev_es_guest(kvm)) { + ret = migrate_vmsa_from(kvm, source_kvm); + if (ret) + goto out_source; + } migrate_info_from(dst_sev, &to_kvm_svm(source_kvm)->sev_info); ret = 0;