KVM: X86: Introduce KVM_HC_MAP_GPA_RANGE hypercall

This hypercall is used by the SEV guest to notify a change in the page
encryption status to the hypervisor. The hypercall should be invoked
only when the encryption attribute is changed from encrypted -> decrypted
and vice versa. By default all guest pages are considered encrypted.

The hypercall exits to userspace to manage the guest shared regions and
integrate with the userspace VMM's migration code.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Steve Rutherford <srutherford@google.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Co-developed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <90778988e1ee01926ff9cac447aacb745f954c8c.1623174621.git.ashish.kalra@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 61 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a0c29e29dd48..e11d64aa0bcd 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1087,6 +1087,8 @@ struct kvm_arch {
 	u32 user_space_msr_mask;
 	struct kvm_x86_msr_filter __rcu *msr_filter;
 
+	u32 hypercall_exit_enabled;
+
 	/* Guest can access the SGX PROVISIONKEY. */
 	bool sgx_provisioning_allowed;
 
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 950afebfba88..5146bbab84d4 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -33,6 +33,8 @@
 #define KVM_FEATURE_PV_SCHED_YIELD	13
 #define KVM_FEATURE_ASYNC_PF_INT	14
 #define KVM_FEATURE_MSI_EXT_DEST_ID	15
+#define KVM_FEATURE_HC_MAP_GPA_RANGE	16
+#define KVM_FEATURE_MIGRATION_CONTROL	17
 
 #define KVM_HINTS_REALTIME      0
 
@@ -54,6 +56,7 @@
 #define MSR_KVM_POLL_CONTROL	0x4b564d05
 #define MSR_KVM_ASYNC_PF_INT	0x4b564d06
 #define MSR_KVM_ASYNC_PF_ACK	0x4b564d07
+#define MSR_KVM_MIGRATION_CONTROL	0x4b564d08
 
 struct kvm_steal_time {
 	__u64 steal;
@@ -90,6 +93,16 @@ struct kvm_clock_pairing {
 /* MSR_KVM_ASYNC_PF_INT */
 #define KVM_ASYNC_PF_VEC_MASK			GENMASK(7, 0)
 
+/* MSR_KVM_MIGRATION_CONTROL */
+#define KVM_MIGRATION_READY		(1 << 0)
+
+/* KVM_HC_MAP_GPA_RANGE */
+#define KVM_MAP_GPA_RANGE_PAGE_SZ_4K	0
+#define KVM_MAP_GPA_RANGE_PAGE_SZ_2M	(1 << 0)
+#define KVM_MAP_GPA_RANGE_PAGE_SZ_1G	(1 << 1)
+#define KVM_MAP_GPA_RANGE_ENC_STAT(n)	(n << 4)
+#define KVM_MAP_GPA_RANGE_ENCRYPTED	KVM_MAP_GPA_RANGE_ENC_STAT(1)
+#define KVM_MAP_GPA_RANGE_DECRYPTED	KVM_MAP_GPA_RANGE_ENC_STAT(0)
 
 /* Operations for KVM_HC_MMU_OP */
 #define KVM_MMU_OP_WRITE_PTE            1
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ceb60f64085c..8b898ec8d349 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -103,6 +103,8 @@ static u64 __read_mostly efer_reserved_bits = ~((u64)EFER_SCE);
 
 static u64 __read_mostly cr4_reserved_bits = CR4_RESERVED_BITS;
 
+#define KVM_EXIT_HYPERCALL_VALID_MASK (1 << KVM_HC_MAP_GPA_RANGE)
+
 #define KVM_X2APIC_API_VALID_FLAGS (KVM_X2APIC_API_USE_32BIT_IDS | \
                                     KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK)
 
@@ -3996,6 +3998,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_SREGS2:
 		r = 1;
 		break;
+	case KVM_CAP_EXIT_HYPERCALL:
+		r = KVM_EXIT_HYPERCALL_VALID_MASK;
+		break;
 	case KVM_CAP_SET_GUEST_DEBUG2:
 		return KVM_GUESTDBG_VALID_MASK;
 #ifdef CONFIG_KVM_XEN
@@ -5622,6 +5627,14 @@ split_irqchip_unlock:
 		if (kvm_x86_ops.vm_copy_enc_context_from)
 			r = kvm_x86_ops.vm_copy_enc_context_from(kvm, cap->args[0]);
 		return r;
+	case KVM_CAP_EXIT_HYPERCALL:
+		if (cap->args[0] & ~KVM_EXIT_HYPERCALL_VALID_MASK) {
+			r = -EINVAL;
+			break;
+		}
+		kvm->arch.hypercall_exit_enabled = cap->args[0];
+		r = 0;
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -8548,6 +8561,17 @@ no_yield:
 	return;
 }
 
+static int complete_hypercall_exit(struct kvm_vcpu *vcpu)
+{
+	u64 ret = vcpu->run->hypercall.ret;
+
+	if (!is_64_bit_mode(vcpu))
+		ret = (u32)ret;
+	kvm_rax_write(vcpu, ret);
+	++vcpu->stat.hypercalls;
+	return kvm_skip_emulated_instruction(vcpu);
+}
+
 int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 {
 	unsigned long nr, a0, a1, a2, a3, ret;
@@ -8613,6 +8637,28 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 		kvm_sched_yield(vcpu, a0);
 		ret = 0;
 		break;
+	case KVM_HC_MAP_GPA_RANGE: {
+		u64 gpa = a0, npages = a1, attrs = a2;
+
+		ret = -KVM_ENOSYS;
+		if (!(vcpu->kvm->arch.hypercall_exit_enabled & (1 << KVM_HC_MAP_GPA_RANGE)))
+			break;
+
+		if (!PAGE_ALIGNED(gpa) || !npages ||
+		    gpa_to_gfn(gpa) + npages <= gpa_to_gfn(gpa)) {
+			ret = -KVM_EINVAL;
+			break;
+		}
+
+		vcpu->run->exit_reason        = KVM_EXIT_HYPERCALL;
+		vcpu->run->hypercall.nr       = KVM_HC_MAP_GPA_RANGE;
+		vcpu->run->hypercall.args[0]  = gpa;
+		vcpu->run->hypercall.args[1]  = npages;
+		vcpu->run->hypercall.args[2]  = attrs;
+		vcpu->run->hypercall.longmode = op_64_bit;
+		vcpu->arch.complete_userspace_io = complete_hypercall_exit;
+		return 0;
+	}
 	default:
 		ret = -KVM_ENOSYS;
 		break;