linux-kernel - [PATCH] Add KVM_EXIT_SHUTDOWN metadata for SEV-ES

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Date:   Mon, 21 Mar 2022 08:02:14 -0700
From:   Peter Gonda <pgonda@...gle.com>
To:     kvm@...r.kernel.org
Cc:     Peter Gonda <pgonda@...gle.com>, Borislav Petkov <bp@...en8.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Brijesh Singh <brijesh.singh@....com>,
        Joerg Roedel <jroedel@...e.de>, Marc Orr <marcorr@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Add KVM_EXIT_SHUTDOWN metadata for SEV-ES

SEV-ES guests can request termination using the GHCB's MSR protocol. See
AMD's GHCB spec section '4.1.13 Termination Request'. Currently when a
guest does this the userspace VMM sees an KVM_EXIT_UNKNOWN (-EVINAL)
return code from KVM_RUN. By adding a KVM_EXIT_SHUTDOWN_ENTRY to kvm_run
struct the userspace VMM can clearly see the guest has requested a SEV-ES
termination including the termination reason code set and reason code.

Signed-off-by: Peter Gonda <pgonda@...gle.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Brijesh Singh <brijesh.singh@....com>
Cc: Joerg Roedel <jroedel@...e.de>
Cc: Marc Orr <marcorr@...gle.com>
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org

---

Tested by making an SEV-ES guest call sev_es_terminate() with hardcoded
reason code set and reason code and then observing the codes from the
userspace VMM in the kvm_run.shutdown.data fields.

---
 arch/x86/kvm/svm/sev.c   |  9 +++++++--
 include/uapi/linux/kvm.h | 12 ++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 75fa6dd268f0..5f9d37dd3f6f 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2735,8 +2735,13 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 		pr_info("SEV-ES guest requested termination: %#llx:%#llx\n",
 			reason_set, reason_code);
 
-		ret = -EINVAL;
-		break;
+		vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
+		vcpu->run->shutdown.reason = KVM_SHUTDOWN_SEV_TERM;
+		vcpu->run->shutdown.ndata = 2;
+		vcpu->run->shutdown.data[0] = reason_set;
+		vcpu->run->shutdown.data[1] = reason_code;
+
+		return 0;
 	}
 	default:
 		/* Error, keep GHCB MSR value as-is */
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 8616af85dc5d..12138b8f290c 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -271,6 +271,12 @@ struct kvm_xen_exit {
 #define KVM_EXIT_XEN              34
 #define KVM_EXIT_RISCV_SBI        35
 
+/* For KVM_EXIT_SHUTDOWN */
+/* Standard VM shutdown request. No additional metadata provided. */
+#define KVM_SHUTDOWN_REQ	0
+/* SEV-ES termination request */
+#define KVM_SHUTDOWN_SEV_TERM	1
+
 /* For KVM_EXIT_INTERNAL_ERROR */
 /* Emulate instruction failed. */
 #define KVM_INTERNAL_ERROR_EMULATION	1
@@ -311,6 +317,12 @@ struct kvm_run {
 		struct {
 			__u64 hardware_exit_reason;
 		} hw;
+		/* KVM_EXIT_SHUTDOWN_ENTRY */
+		struct {
+			__u64 reason;
+			__u32 ndata;
+			__u64 data[16];
+		} shutdown;
 		/* KVM_EXIT_FAIL_ENTRY */
 		struct {
 			__u64 hardware_entry_failure_reason;
-- 
2.35.1.894.gb6a874cedc-goog