linux-kernel - [PATCH 06/18] KVM: x86: hyper-v: Exit on Get/SetVpRegisters hcall

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Message-ID: <20240609154945.55332-7-nsaenz@amazon.com>
Date: Sun, 9 Jun 2024 15:49:35 +0000
From: Nicolas Saenz Julienne <nsaenz@...zon.com>
To: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>
CC: <pbonzini@...hat.com>, <seanjc@...gle.com>, <vkuznets@...hat.com>,
	<linux-doc@...r.kernel.org>, <linux-hyperv@...r.kernel.org>,
	<linux-arch@...r.kernel.org>, <linux-trace-kernel@...r.kernel.org>,
	<graf@...zon.de>, <dwmw2@...radead.org>, <paul@...zon.com>,
	<nsaenz@...zon.com>, <mlevitsk@...hat.com>, <jgowans@...zon.com>,
	<corbet@....net>, <decui@...rosoft.com>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>,
	<x86@...nel.org>, <amoorthy@...gle.com>
Subject: [PATCH 06/18] KVM: x86: hyper-v: Exit on Get/SetVpRegisters hcall

Let user-space handle HvGetVpRegisters and HvSetVpRegisters as they are
VTL aware hypercalls used solely in the context of VSM. Additionally,
expose the cpuid bit.

Signed-off-by: Nicolas Saenz Julienne <nsaenz@...zon.com>
---
 Documentation/virt/kvm/api.rst    | 10 ++++++++++
 arch/x86/kvm/hyperv.c             | 15 +++++++++++++++
 include/asm-generic/hyperv-tlfs.h |  1 +
 3 files changed, 26 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index e664c54a13b04..05b01b00a395c 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8931,3 +8931,13 @@ CPUIDs map to KVM functionality.
 This CPUID indicates that KVM supports retuning data to the guest in response
 to a hypercall using the XMM registers. It also extends ``struct
 kvm_hyperv_exit`` to allow passing the XMM data from userspace.
+
+10.2 HV_ACCESS_VP_REGISTERS
+---------------------------
+
+:Location: CPUID.40000003H:EBX[bit 17]
+
+This CPUID indicates that KVM supports HvGetVpRegisters and HvSetVpRegisters.
+Currently, it is only used in conjunction with HV_ACCESS_VSM, and immediately
+exits to userspace with KVM_EXIT_HYPERV_HCALL as the reason. Userspace is
+expected to complete the hypercall before resuming execution.
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index d00baf3ffb165..d0edc2bec5a4f 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2425,6 +2425,11 @@ static void kvm_hv_write_xmm(struct kvm_hyperv_xmm_reg *xmm)
 
 static bool kvm_hv_is_xmm_output_hcall(u16 code)
 {
+	switch (code) {
+	case HVCALL_GET_VP_REGISTERS:
+		return true;
+	}
+
 	return false;
 }
 
@@ -2505,6 +2510,8 @@ static bool is_xmm_fast_hypercall(struct kvm_hv_hcall *hc)
 	case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX:
 	case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX:
 	case HVCALL_SEND_IPI_EX:
+	case HVCALL_GET_VP_REGISTERS:
+	case HVCALL_SET_VP_REGISTERS:
 		return true;
 	}
 
@@ -2543,6 +2550,10 @@ static bool hv_check_hypercall_access(struct kvm_vcpu_hv *hv_vcpu, u16 code)
 		 */
 		return !kvm_hv_is_syndbg_enabled(hv_vcpu->vcpu) ||
 			hv_vcpu->cpuid_cache.features_ebx & HV_DEBUGGING;
+	case HVCALL_GET_VP_REGISTERS:
+	case HVCALL_SET_VP_REGISTERS:
+		return hv_vcpu->cpuid_cache.features_ebx &
+			HV_ACCESS_VP_REGISTERS;
 	case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX:
 	case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX:
 		if (!(hv_vcpu->cpuid_cache.enlightenments_eax &
@@ -2727,6 +2738,9 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 			break;
 		}
 		goto hypercall_userspace_exit;
+	case HVCALL_GET_VP_REGISTERS:
+	case HVCALL_SET_VP_REGISTERS:
+		goto hypercall_userspace_exit;
 	default:
 		ret = HV_STATUS_INVALID_HYPERCALL_CODE;
 		break;
@@ -2898,6 +2912,7 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
 			ent->ebx |= HV_POST_MESSAGES;
 			ent->ebx |= HV_SIGNAL_EVENTS;
 			ent->ebx |= HV_ENABLE_EXTENDED_HYPERCALLS;
+			ent->ebx |= HV_ACCESS_VP_REGISTERS;
 
 			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 28cde641b5474..9e909f0834598 100644
--- a/include/asm-generic/hyperv-tlfs.h
+++ b/include/asm-generic/hyperv-tlfs.h
@@ -90,6 +90,7 @@
 #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)
 
-- 
2.40.1