Re: [PATCH Part2 v6 24/49] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_START command

Peter Gonda
2022-06-24T14:43:28Z

>
> +19. KVM_SNP_LAUNCH_START
> +------------------------
> +
> +The KVM_SNP_LAUNCH_START command is used for creating the memory encryption
> +context for the SEV-SNP guest. To create the encryption context, user must
> +provide a guest policy, migration agent (if any) and guest OS visible
> +workarounds value as defined SEV-SNP specification.
> +
> +Parameters (in): struct kvm_snp_launch_start
> +
> +Returns: 0 on success, -negative on error
> +
> +::
> +
> + struct kvm_sev_snp_launch_start {
> + __u64 policy; /* Guest policy to use. */
> + __u64 ma_uaddr; /* userspace address of migration agent */
> + __u8 ma_en; /* 1 if the migtation agent is enabled */

migration

> + __u8 imi_en; /* set IMI to 1. */
> + __u8 gosvw[16]; /* guest OS visible workarounds */
> + };
> +
> +See the SEV-SNP specification for further detail on the launch input.
> +
> References
> ==========
>

>
> +static int snp_decommission_context(struct kvm *kvm)
> +{
> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> + struct sev_data_snp_decommission data = {};
> + int ret;
> +
> + /* If context is not created then do nothing */
> + if (!sev->snp_context)
> + return 0;
> +
> + data.gctx_paddr = __sme_pa(sev->snp_context);
> + ret = snp_guest_decommission(&data, NULL);

Do we have a similar race like in sev_unbind_asid() with DEACTIVATE
and WBINVD/DF_FLUSH? The SNP_DECOMMISSION spec looks quite similar to
DEACTIVATE.

> + if (WARN_ONCE(ret, "failed to release guest context"))
> + return ret;
> +
> + /* free the context page now */
> + snp_free_firmware_page(sev->snp_context);
> + sev->snp_context = NULL;
> +
> + return 0;
> +}
> +
> void sev_vm_destroy(struct kvm *kvm)
> {
> struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;