[PATCH Part2 v6 36/49] KVM: SVM: Add support to handle GHCB GPA register VMGEXIT

Ashish Kalra
2022-06-20T23:11:28Z

From: Brijesh Singh <brijesh.singh@amd.com>

SEV-SNP guests are required to perform a GHCB GPA registration. Before
using a GHCB GPA for a vCPU the first time, a guest must register the
vCPU GHCB GPA. If hypervisor can work with the guest requested GPA then
it must respond back with the same GPA otherwise return -1.

On VMEXIT, Verify that GHCB GPA matches with the registered value. If a
mismatch is detected then abort the guest.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/include/asm/sev-common.h | 8 ++++++++
arch/x86/kvm/svm/sev.c | 27 +++++++++++++++++++++++++++
arch/x86/kvm/svm/svm.h | 7 +++++++
3 files changed, 42 insertions(+)

diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index 539de6b93420..0a9055cdfae2 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -59,6 +59,14 @@
#define GHCB_MSR_AP_RESET_HOLD_RESULT_POS 12
#define GHCB_MSR_AP_RESET_HOLD_RESULT_MASK GENMASK_ULL(51, 0)

+/* Preferred GHCB GPA Request */
+#define GHCB_MSR_PREF_GPA_REQ 0x010
+#define GHCB_MSR_GPA_VALUE_POS 12
+#define GHCB_MSR_GPA_VALUE_MASK GENMASK_ULL(51, 0)
+
+#define GHCB_MSR_PREF_GPA_RESP 0x011
+#define GHCB_MSR_PREF_GPA_NONE 0xfffffffffffff
+
/* GHCB GPA Register */
#define GHCB_MSR_REG_GPA_REQ 0x012
#define GHCB_MSR_REG_GPA_REQ_VAL(v) \
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index c70f3f7e06a8..6de48130e414 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3331,6 +3331,27 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
GHCB_MSR_INFO_MASK, GHCB_MSR_INFO_POS);
break;
}
+ case GHCB_MSR_PREF_GPA_REQ: {
+ set_ghcb_msr_bits(svm, GHCB_MSR_PREF_GPA_NONE, GHCB_MSR_GPA_VALUE_MASK,
+ GHCB_MSR_GPA_VALUE_POS);
+ set_ghcb_msr_bits(svm, GHCB_MSR_PREF_GPA_RESP, GHCB_MSR_INFO_MASK,
+ GHCB_MSR_INFO_POS);
+ break;
+ }
+ case GHCB_MSR_REG_GPA_REQ: {
+ u64 gfn;
+
+ gfn = get_ghcb_msr_bits(svm, GHCB_MSR_GPA_VALUE_MASK,
+ GHCB_MSR_GPA_VALUE_POS);
+
+ svm->sev_es.ghcb_registered_gpa = gfn_to_gpa(gfn);
+
+ set_ghcb_msr_bits(svm, gfn, GHCB_MSR_GPA_VALUE_MASK,
+ GHCB_MSR_GPA_VALUE_POS);
+ set_ghcb_msr_bits(svm, GHCB_MSR_REG_GPA_RESP, GHCB_MSR_INFO_MASK,
+ GHCB_MSR_INFO_POS);
+ break;
+ }
case GHCB_MSR_TERM_REQ: {
u64 reason_set, reason_code;

@@ -3381,6 +3402,12 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
return 1;
}

+ /* SEV-SNP guest requires that the GHCB GPA must be registered */
+ if (sev_snp_guest(svm->vcpu.kvm) && !ghcb_gpa_is_registered(svm, ghcb_gpa)) {
+ vcpu_unimpl(&svm->vcpu, "vmgexit: GHCB GPA [%#llx] is not registered.\n", ghcb_gpa);
+ return -EINVAL;
+ }
+
ret = sev_es_validate_vmgexit(svm, &exit_code);
if (ret)
return ret;
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index c80352c9c0d6..54ff56cb6125 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -206,6 +206,8 @@ struct vcpu_sev_es_state {
*/
u64 ghcb_sw_exit_info_1;
u64 ghcb_sw_exit_info_2;
+
+ u64 ghcb_registered_gpa;
};

struct vcpu_svm {
@@ -334,6 +336,11 @@ static inline bool sev_snp_guest(struct kvm *kvm)
return sev_es_guest(kvm) && sev->snp_active;
}

+static inline bool ghcb_gpa_is_registered(struct vcpu_svm *svm, u64 val)
+{
+ return svm->sev_es.ghcb_registered_gpa == val;
+}
+
static inline void vmcb_mark_all_dirty(struct vmcb *vmcb)
{
vmcb->control.clean = 0;
--
2.25.1