[PATCH 2/6] KVM: SVM: Add support for the SEV-SNP #HV doorbell page NAE event

Melody Wang
2024-08-07T00:59:21Z

To support the SEV-SNP Restricted Injection feature, the SEV-SNP guest must
register a #HV doorbell page for use with the #HV.

The #HV doorbell page NAE event allows the guest to register a #HV doorbell
page. The NAE event consists of four actions: GET_PREFERRED, SET, QUERY, CLEAR.
Implement the NAE event as per GHCB specification.

Co-developed-by: Thomas Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Thomas Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Melody Wang <huibo.wang@amd.com>
---
arch/x86/include/uapi/asm/svm.h | 5 +++
arch/x86/kvm/svm/sev.c | 73 +++++++++++++++++++++++++++++++++
arch/x86/kvm/svm/svm.h | 2 +
3 files changed, 80 insertions(+)

diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
index 1814b413fd57..7905c9be44d1 100644
--- a/arch/x86/include/uapi/asm/svm.h
+++ b/arch/x86/include/uapi/asm/svm.h
@@ -115,6 +115,11 @@
#define SVM_VMGEXIT_AP_CREATE_ON_INIT 0
#define SVM_VMGEXIT_AP_CREATE 1
#define SVM_VMGEXIT_AP_DESTROY 2
+#define SVM_VMGEXIT_HVDB_PAGE 0x80000014
+#define SVM_VMGEXIT_HVDB_GET_PREFERRED 0
+#define SVM_VMGEXIT_HVDB_SET 1
+#define SVM_VMGEXIT_HVDB_QUERY 2
+#define SVM_VMGEXIT_HVDB_CLEAR 3
#define SVM_VMGEXIT_SNP_RUN_VMPL 0x80000018
#define SVM_VMGEXIT_HV_FEATURES 0x8000fffd
#define SVM_VMGEXIT_TERM_REQUEST 0x8000fffe
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 532df12b43c5..19ee3f083cad 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3409,6 +3409,10 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
control->exit_info_1 == control->exit_info_2)
goto vmgexit_err;
break;
+ case SVM_VMGEXIT_HVDB_PAGE:
+ if (!sev_snp_guest(vcpu->kvm))
+ goto vmgexit_err;
+ break;
default:
reason = GHCB_ERR_INVALID_EVENT;
goto vmgexit_err;
@@ -4124,6 +4128,66 @@ static int snp_handle_ext_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t r
return 1; /* resume guest */
}

+static int sev_snp_hv_doorbell_page(struct vcpu_svm *svm)
+{
+ struct kvm_vcpu *vcpu = &svm->vcpu;
+ struct kvm_host_map hvdb_map;
+ gpa_t hvdb_gpa;
+ u64 request;
+
+ if (!sev_snp_guest(vcpu->kvm))
+ return -EINVAL;
+
+ request = svm->vmcb->control.exit_info_1;
+ hvdb_gpa = svm->vmcb->control.exit_info_2;
+
+ switch (request) {
+ case SVM_VMGEXIT_HVDB_GET_PREFERRED:
+ ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, ~0ULL);
+ break;
+ case SVM_VMGEXIT_HVDB_SET:
+ svm->sev_es.hvdb_gpa = INVALID_PAGE;
+
+ if (!PAGE_ALIGNED(hvdb_gpa)) {
+ vcpu_unimpl(vcpu, "vmgexit: unaligned #HV doorbell page address [%#llx] from guest\n",
+ hvdb_gpa);
+ return -EINVAL;
+ }
+
+ if (!page_address_valid(vcpu, hvdb_gpa)) {
+ vcpu_unimpl(vcpu, "vmgexit: invalid #HV doorbell page address [%#llx] from guest\n",
+ hvdb_gpa);
+ return -EINVAL;
+ }
+
+ /* Map and unmap the GPA just to be sure the GPA is valid */
+ if (kvm_vcpu_map(vcpu, gpa_to_gfn(hvdb_gpa), &hvdb_map)) {
+ /* Unable to map #HV doorbell page from guest */
+ vcpu_unimpl(vcpu, "vmgexit: error mapping #HV doorbell page [%#llx] from guest\n",
+ hvdb_gpa);
+ return -EINVAL;
+ }
+ kvm_vcpu_unmap(vcpu, &hvdb_map, true);
+
+ svm->sev_es.hvdb_gpa = hvdb_gpa;
+ fallthrough;
+ case SVM_VMGEXIT_HVDB_QUERY:
+ ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, svm->sev_es.hvdb_gpa);
+ break;
+ case SVM_VMGEXIT_HVDB_CLEAR:
+ svm->sev_es.hvdb_gpa = INVALID_PAGE;
+ break;
+ default:
+ svm->sev_es.hvdb_gpa = INVALID_PAGE;
+
+ vcpu_unimpl(vcpu, "vmgexit: invalid #HV doorbell page request [%#llx] from guest\n",
+ request);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
{
struct vmcb_control_area *control = &svm->vmcb->control;
@@ -4404,6 +4468,14 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
case SVM_VMGEXIT_EXT_GUEST_REQUEST:
ret = snp_handle_ext_guest_req(svm, control->exit_info_1, control->exit_info_2);
break;
+ case SVM_VMGEXIT_HVDB_PAGE:
+ if (sev_snp_hv_doorbell_page(svm)) {
+ ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, 2);
+ ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, GHCB_ERR_INVALID_INPUT);
+ }
+
+ ret = 1;
+ break;
case SVM_VMGEXIT_UNSUPPORTED_EVENT:
vcpu_unimpl(vcpu,
"vmgexit: unsupported event - exit_info_1=%#llx, exit_info_2=%#llx\n",
@@ -4571,6 +4643,7 @@ void sev_es_vcpu_reset(struct vcpu_svm *svm)
sev_enc_bit));

mutex_init(&svm->sev_es.snp_vmsa_mutex);
+ svm->sev_es.hvdb_gpa = INVALID_PAGE;
}

void sev_es_prepare_switch_to_guest(struct vcpu_svm *svm, struct sev_es_save_area *hostsa)
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 76107c7d0595..f0f14801e122 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -225,6 +225,8 @@ struct vcpu_sev_es_state {
gpa_t snp_vmsa_gpa;
bool snp_ap_waiting_for_reset;
bool snp_has_guest_vmsa;
+
+ gpa_t hvdb_gpa;
};

struct vcpu_svm {
--
2.34.1