[PATCH Part2 RFC v3 01/37] KVM: SVM: Add support to handle AP reset MSR protocol

[Brijesh Singh <brijesh.singh@xxxxxxx>]

From: Tom Lendacky <thomas.lendacky@xxxxxxx>

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@xxxxxxx>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
 arch/x86/include/asm/sev-common.h |  6 ++++
 arch/x86/kvm/svm/sev.c            | 56 ++++++++++++++++++++++++++-----
 arch/x86/kvm/svm/svm.h            |  1 +
 3 files changed, 55 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index 47aa57bf654a..97137f1a567b 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -45,6 +45,12 @@
 		(((unsigned long)reg & GHCB_MSR_CPUID_REG_MASK) << GHCB_MSR_CPUID_REG_POS) | \
 		(((unsigned long)fn) << GHCB_MSR_CPUID_FUNC_POS))
 
+/* AP Reset Hold */
+#define GHCB_MSR_AP_RESET_HOLD_REQ		0x006
+#define GHCB_MSR_AP_RESET_HOLD_RESP		0x007
+#define GHCB_MSR_AP_RESET_HOLD_RESULT_POS	12
+#define GHCB_MSR_AP_RESET_HOLD_RESULT_MASK	GENMASK_ULL(51, 0)
+
 /* GHCB Hypervisor Feature Request */
 #define GHCB_MSR_HV_FT_REQ	0x080
 #define GHCB_MSR_HV_FT_RESP	0x081
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index d93a1c368b61..7d0b98dbe523 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -57,6 +57,10 @@ module_param_named(sev_es, sev_es_enabled, bool, 0444);
 #define sev_es_enabled false
 #endif /* CONFIG_KVM_AMD_SEV */
 
+#define AP_RESET_HOLD_NONE		0
+#define AP_RESET_HOLD_NAE_EVENT		1
+#define AP_RESET_HOLD_MSR_PROTO		2
+
 static u8 sev_enc_bit;
 static DECLARE_RWSEM(sev_deactivate_lock);
 static DEFINE_MUTEX(sev_bitmap_lock);
@@ -2199,6 +2203,9 @@ 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->ap_reset_hold_type = AP_RESET_HOLD_NONE;
+
 	if (!svm->ghcb)
 		return;
 
@@ -2404,6 +2411,22 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 				  GHCB_MSR_INFO_POS);
 		break;
 	}
+	case GHCB_MSR_AP_RESET_HOLD_REQ:
+		svm->ap_reset_hold_type = AP_RESET_HOLD_MSR_PROTO;
+		ret = kvm_emulate_ap_reset_hold(&svm->vcpu);
+
+		/*
+		 * Preset the result to a non-SIPI return and then only set
+		 * the result to non-zero when delivering a SIPI.
+		 */
+		set_ghcb_msr_bits(svm, 0,
+				  GHCB_MSR_AP_RESET_HOLD_RESULT_MASK,
+				  GHCB_MSR_AP_RESET_HOLD_RESULT_POS);
+
+		set_ghcb_msr_bits(svm, GHCB_MSR_AP_RESET_HOLD_RESP,
+				  GHCB_MSR_INFO_MASK,
+				  GHCB_MSR_INFO_POS);
+		break;
 	case GHCB_MSR_TERM_REQ: {
 		u64 reason_set, reason_code;
 
@@ -2491,6 +2514,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
 		ret = svm_invoke_exit_handler(vcpu, SVM_EXIT_IRET);
 		break;
 	case SVM_VMGEXIT_AP_HLT_LOOP:
+		svm->ap_reset_hold_type = AP_RESET_HOLD_NAE_EVENT;
 		ret = kvm_emulate_ap_reset_hold(vcpu);
 		break;
 	case SVM_VMGEXIT_AP_JUMP_TABLE: {
@@ -2628,13 +2652,29 @@ 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;
+	/* Subsequent SIPI */
+	switch (svm->ap_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.
+		 */
+		set_ghcb_msr_bits(svm, 1,
+				  GHCB_MSR_AP_RESET_HOLD_RESULT_MASK,
+				  GHCB_MSR_AP_RESET_HOLD_RESULT_POS);
 
-	ghcb_set_sw_exit_info_2(svm->ghcb, 1);
+		set_ghcb_msr_bits(svm, GHCB_MSR_AP_RESET_HOLD_RESP,
+				  GHCB_MSR_INFO_MASK,
+				  GHCB_MSR_INFO_POS);
+		break;
+	default:
+		break;
+	}
 }
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 0b89aee51b74..ad12ca26b2d8 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -174,6 +174,7 @@ struct vcpu_svm {
 	struct ghcb *ghcb;
 	struct kvm_host_map ghcb_map;
 	bool received_first_sipi;
+	unsigned int ap_reset_hold_type;
 
 	/* SEV-ES scratch area support */
 	void *ghcb_sa;
-- 
2.17.1