linux-kernel - [RFC 12/33] KVM: x86: hyper-v: Handle VSM hcalls in user-space

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Message-ID: <20231108111806.92604-13-nsaenz@amazon.com>
Date:   Wed, 8 Nov 2023 11:17:45 +0000
From:   Nicolas Saenz Julienne <nsaenz@...zon.com>
To:     <kvm@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-hyperv@...r.kernel.org>,
        <pbonzini@...hat.com>, <seanjc@...gle.com>, <vkuznets@...hat.com>,
        <anelkz@...zon.com>, <graf@...zon.com>, <dwmw@...zon.co.uk>,
        <jgowans@...zon.com>, <corbert@....net>, <kys@...rosoft.com>,
        <haiyangz@...rosoft.com>, <decui@...rosoft.com>, <x86@...nel.org>,
        <linux-doc@...r.kernel.org>,
        Nicolas Saenz Julienne <nsaenz@...zon.com>
Subject: [RFC 12/33] KVM: x86: hyper-v: Handle VSM hcalls in user-space

Let user-space handle all hypercalls that fall under the AccessVsm
partition privilege flag. That is:
 - HVCALL_MODIFY_VTL_PROTECTION_MASK:
 - HVCALL_ENABLE_PARTITION_VTL:
 - HVCALL_ENABLE_VP_VTL:
 - HVCALL_VTL_CALL:
 - HVCALL_VTL_RETURN:
The hypercalls are processed through the KVM_EXIT_HYPERV_HVCALL exit.
Additionally, expose the cpuid bit.

Signed-off-by: Nicolas Saenz Julienne <nsaenz@...zon.com>
---
 arch/x86/kvm/hyperv.c             | 15 +++++++++++++++
 include/asm-generic/hyperv-tlfs.h |  7 ++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index a3970d52eef1..a266c5d393f5 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2462,6 +2462,11 @@ static bool kvm_hv_is_xmm_output_hcall(u16 code)
 	return false;
 }
 
+static inline bool kvm_hv_is_vtl_call_return(u16 code)
+{
+	return code == HVCALL_VTL_CALL || code == HVCALL_VTL_RETURN;
+}
+
 static int kvm_hv_hypercall_complete_userspace(struct kvm_vcpu *vcpu)
 {
 	bool fast = !!(vcpu->run->hyperv.u.hcall.input & HV_HYPERCALL_FAST_BIT);
@@ -2471,6 +2476,9 @@ static int kvm_hv_hypercall_complete_userspace(struct kvm_vcpu *vcpu)
 	if (kvm_hv_is_xmm_output_hcall(code) && hv_result_success(result) && fast)
 		kvm_hv_write_xmm(vcpu->run->hyperv.u.hcall.xmm);
 
+	if (kvm_hv_is_vtl_call_return(code))
+		return kvm_skip_emulated_instruction(vcpu);
+
 	return kvm_hv_hypercall_complete(vcpu, result);
 }
 
@@ -2525,6 +2533,7 @@ static bool is_xmm_fast_hypercall(struct kvm_hv_hcall *hc)
 	case HVCALL_SEND_IPI_EX:
 	case HVCALL_GET_VP_REGISTERS:
 	case HVCALL_SET_VP_REGISTERS:
+	case HVCALL_MODIFY_VTL_PROTECTION_MASK:
 		return true;
 	}
 
@@ -2745,6 +2754,11 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 		goto hypercall_userspace_exit;
 	case HVCALL_GET_VP_REGISTERS:
 	case HVCALL_SET_VP_REGISTERS:
+	case HVCALL_MODIFY_VTL_PROTECTION_MASK:
+	case HVCALL_ENABLE_PARTITION_VTL:
+	case HVCALL_ENABLE_VP_VTL:
+	case HVCALL_VTL_CALL:
+	case HVCALL_VTL_RETURN:
 		goto hypercall_userspace_exit;
 	default:
 		ret = HV_STATUS_INVALID_HYPERCALL_CODE;
@@ -2912,6 +2926,7 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
 			ent->ebx |= HV_SIGNAL_EVENTS;
 			ent->ebx |= HV_ENABLE_EXTENDED_HYPERCALLS;
 			ent->ebx |= HV_ACCESS_VP_REGISTERS;
+			ent->ebx |= HV_ACCESS_VSM;
 
 			ent->edx |= HV_X64_HYPERCALL_XMM_INPUT_AVAILABLE;
 			ent->edx |= HV_X64_HYPERCALL_XMM_OUTPUT_AVAILABLE;
diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
index 24ea699a3d8e..a8b5c8a84bbc 100644
--- a/include/asm-generic/hyperv-tlfs.h
+++ b/include/asm-generic/hyperv-tlfs.h
@@ -89,6 +89,7 @@
 #define HV_ACCESS_STATS				BIT(8)
 #define HV_DEBUGGING				BIT(11)
 #define HV_CPU_MANAGEMENT			BIT(12)
+#define HV_ACCESS_VSM				BIT(16)
 #define HV_ACCESS_VP_REGISTERS			BIT(17)
 #define HV_ENABLE_EXTENDED_HYPERCALLS		BIT(20)
 #define HV_ISOLATION				BIT(22)
@@ -147,9 +148,13 @@ union hv_reference_tsc_msr {
 /* Declare the various hypercall operations. */
 #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE	0x0002
 #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST	0x0003
-#define HVCALL_ENABLE_VP_VTL			0x000f
 #define HVCALL_NOTIFY_LONG_SPIN_WAIT		0x0008
 #define HVCALL_SEND_IPI				0x000b
+#define HVCALL_MODIFY_VTL_PROTECTION_MASK	0x000c
+#define HVCALL_ENABLE_PARTITION_VTL		0x000d
+#define HVCALL_ENABLE_VP_VTL			0x000f
+#define HVCALL_VTL_CALL				0x0011
+#define HVCALL_VTL_RETURN			0x0012
 #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX	0x0013
 #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX	0x0014
 #define HVCALL_SEND_IPI_EX			0x0015
-- 
2.40.1