[PATCH v5 4/6] KVM: SVM: Add support to handle AP reset MSR protocol

Joerg Roedel
2021-10-20T12:44:45Z

From: Tom Lendacky <thomas.lendacky@amd.com>

Add support for AP Reset Hold being invoked using the GHCB MSR protocol,
available in version 2 of the GHCB specification.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/include/asm/kvm_host.h | 1 -
arch/x86/kvm/svm/sev.c | 52 ++++++++++++++++++++++++++-------
arch/x86/kvm/svm/svm.h | 8 +++++
3 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b67f550616cf..5c6b1469cc3b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -237,7 +237,6 @@ enum x86_intercept_stage;
KVM_GUESTDBG_INJECT_DB | \
KVM_GUESTDBG_BLOCKIRQ)

-
#define PFERR_PRESENT_BIT 0
#define PFERR_WRITE_BIT 1
#define PFERR_USER_BIT 2
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 9afa71cb36e6..10af4ac83971 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2246,6 +2246,9 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)

void sev_es_unmap_ghcb(struct vcpu_svm *svm)
{
+ /* Clear any indication that the vCPU is in a type of AP Reset Hold */
+ svm->reset_hold_type = AP_RESET_HOLD_NONE;
+
if (!svm->ghcb)
return;

@@ -2405,14 +2408,21 @@ static u64 ghcb_msr_version_info(void)
return msr;
}

-static int sev_emulate_ap_reset_hold(struct vcpu_svm *svm)
+static int sev_emulate_ap_reset_hold(struct vcpu_svm *svm, enum ap_reset_hold_type type)
{
int ret = kvm_skip_emulated_instruction(&svm->vcpu);

+ svm->reset_hold_type = type;
+
return __kvm_vcpu_halt(&svm->vcpu,
KVM_MP_STATE_AP_RESET_HOLD, KVM_EXIT_AP_RESET_HOLD) && ret;
}

+static u64 ghcb_msr_ap_rst_resp(u64 value)
+{
+ return (u64)GHCB_MSR_AP_RESET_HOLD_RESP | (value << GHCB_DATA_LOW);
+}
+
static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
{
struct vmcb_control_area *control = &svm->vmcb->control;
@@ -2459,6 +2469,16 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)

break;
}
+ case GHCB_MSR_AP_RESET_HOLD_REQ:
+ ret = sev_emulate_ap_reset_hold(svm, AP_RESET_HOLD_MSR_PROTO);
+
+ /*
+ * Preset the result to a non-SIPI return and then only set
+ * the result to non-zero when delivering a SIPI.
+ */
+ svm->vmcb->control.ghcb_gpa = ghcb_msr_ap_rst_resp(0);
+
+ break;
case GHCB_MSR_TERM_REQ: {
u64 reason_set, reason_code;

@@ -2544,7 +2564,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
ret = svm_invoke_exit_handler(vcpu, SVM_EXIT_IRET);
break;
case SVM_VMGEXIT_AP_HLT_LOOP:
- ret = sev_emulate_ap_reset_hold(svm);
+ ret = sev_emulate_ap_reset_hold(svm, AP_RESET_HOLD_NAE_EVENT);
break;
case SVM_VMGEXIT_AP_JUMP_TABLE: {
struct kvm_sev_info *sev = &to_kvm_svm(vcpu->kvm)->sev_info;
@@ -2679,13 +2699,23 @@ void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector)
return;
}

- /*
- * Subsequent SIPI: Return from an AP Reset Hold VMGEXIT, where
- * the guest will set the CS and RIP. Set SW_EXIT_INFO_2 to a
- * non-zero value.
- */
- if (!svm->ghcb)
- return;
-
- ghcb_set_sw_exit_info_2(svm->ghcb, 1);
+ /* Subsequent SIPI */
+ switch (svm->reset_hold_type) {
+ case AP_RESET_HOLD_NAE_EVENT:
+ /*
+ * Return from an AP Reset Hold VMGEXIT, where the guest will
+ * set the CS and RIP. Set SW_EXIT_INFO_2 to a non-zero value.
+ */
+ ghcb_set_sw_exit_info_2(svm->ghcb, 1);
+ break;
+ case AP_RESET_HOLD_MSR_PROTO:
+ /*
+ * Return from an AP Reset Hold VMGEXIT, where the guest will
+ * set the CS and RIP. Set GHCB data field to a non-zero value.
+ */
+ svm->vmcb->control.ghcb_gpa = ghcb_msr_ap_rst_resp(1);
+ break;
+ default:
+ break;
+ }
}
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 68e5f16a0554..bf9379f1cfb8 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -69,6 +69,12 @@ enum {
/* TPR and CR2 are always written before VMRUN */
#define VMCB_ALWAYS_DIRTY_MASK ((1U << VMCB_INTR) | (1U << VMCB_CR2))

+enum ap_reset_hold_type {
+ AP_RESET_HOLD_NONE,
+ AP_RESET_HOLD_NAE_EVENT,
+ AP_RESET_HOLD_MSR_PROTO,
+};
+
struct kvm_sev_info {
bool active; /* SEV enabled guest */
bool es_active; /* SEV-ES enabled guest */
@@ -199,6 +205,8 @@ struct vcpu_svm {
bool ghcb_sa_free;

bool guest_state_loaded;
+
+ enum ap_reset_hold_type reset_hold_type;
};

struct svm_cpu_data {
--
2.33.1