From b5aafcb4efd2bdacbc37753cf807d69faa6a7304 Mon Sep 17 00:00:00 2001 From: Binbin Wu Date: Tue, 10 Jun 2025 10:14:19 +0800 Subject: KVM: TDX: Add new TDVMCALL status code for unsupported subfuncs Add the new TDVMCALL status code TDVMCALL_STATUS_SUBFUNC_UNSUPPORTED and return it for unimplemented TDVMCALL subfunctions. Returning TDVMCALL_STATUS_INVALID_OPERAND when a subfunction is not implemented is vague because TDX guests can't tell the error is due to the subfunction is not supported or an invalid input of the subfunction. New GHCI spec adds TDVMCALL_STATUS_SUBFUNC_UNSUPPORTED to avoid the ambiguity. Use it instead of TDVMCALL_STATUS_INVALID_OPERAND. Before the change, for common guest implementations, when a TDX guest receives TDVMCALL_STATUS_INVALID_OPERAND, it has two cases: 1. Some operand is invalid. It could change the operand to another value retry. 2. The subfunction is not supported. For case 1, an invalid operand usually means the guest implementation bug. Since the TDX guest can't tell which case is, the best practice for handling TDVMCALL_STATUS_INVALID_OPERAND is stopping calling such leaf, treating the failure as fatal if the TDVMCALL is essential or ignoring it if the TDVMCALL is optional. With this change, TDVMCALL_STATUS_SUBFUNC_UNSUPPORTED could be sent to old TDX guest that do not know about it, but it is expected that the guest will make the same action as TDVMCALL_STATUS_INVALID_OPERAND. Currently, no known TDX guest checks TDVMCALL_STATUS_INVALID_OPERAND specifically; for example Linux just checks for success. Signed-off-by: Binbin Wu [Return it for untrapped KVM_HC_MAP_GPA_RANGE. - Paolo] Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/tdx.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'arch/x86/kvm/vmx/tdx.c') diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index b952bc673271..5d100c240ab3 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1212,11 +1212,13 @@ static int tdx_map_gpa(struct kvm_vcpu *vcpu) /* * Converting TDVMCALL_MAP_GPA to KVM_HC_MAP_GPA_RANGE requires * userspace to enable KVM_CAP_EXIT_HYPERCALL with KVM_HC_MAP_GPA_RANGE - * bit set. If not, the error code is not defined in GHCI for TDX, use - * TDVMCALL_STATUS_INVALID_OPERAND for this case. + * bit set. This is a base call so it should always be supported, but + * KVM has no way to ensure that userspace implements the GHCI correctly. + * So if KVM_HC_MAP_GPA_RANGE does not cause a VMEXIT, return an error + * to the guest. */ if (!user_exit_on_hypercall(vcpu->kvm, KVM_HC_MAP_GPA_RANGE)) { - ret = TDVMCALL_STATUS_INVALID_OPERAND; + ret = TDVMCALL_STATUS_SUBFUNC_UNSUPPORTED; goto error; } @@ -1476,7 +1478,7 @@ static int handle_tdvmcall(struct kvm_vcpu *vcpu) break; } - tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_INVALID_OPERAND); + tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_SUBFUNC_UNSUPPORTED); return 1; } -- cgit v1.2.3 From cf207eac06f661fb692f405d5ab8230df884ee52 Mon Sep 17 00:00:00 2001 From: Binbin Wu Date: Tue, 10 Jun 2025 10:14:20 +0800 Subject: KVM: TDX: Handle TDG.VP.VMCALL Handle TDVMCALL for GetQuote to generate a TD-Quote. GetQuote is a doorbell-like interface used by TDX guests to request VMM to generate a TD-Quote signed by a service hosting TD-Quoting Enclave operating on the host. A TDX guest passes a TD Report (TDREPORT_STRUCT) in a shared-memory area as parameter. Host VMM can access it and queue the operation for a service hosting TD-Quoting enclave. When completed, the Quote is returned via the same shared-memory area. KVM only checks the GPA from the TDX guest has the shared-bit set and drops the shared-bit before exiting to userspace to avoid bleeding the shared-bit into KVM's exit ABI. KVM forwards the request to userspace VMM (e.g. QEMU) and userspace VMM queues the operation asynchronously. KVM sets the return code according to the 'ret' field set by userspace to notify the TDX guest whether the request has been queued successfully or not. When the request has been queued successfully, the TDX guest can poll the status field in the shared-memory area to check whether the Quote generation is completed or not. When completed, the generated Quote is returned via the same buffer. Add KVM_EXIT_TDX as a new exit reason to userspace. Userspace is required to handle the KVM exit reason as the initial support for TDX, by reentering KVM to ensure that the TDVMCALL is complete. While at it, add a note that KVM_EXIT_HYPERCALL also requires reentry with KVM_RUN. Signed-off-by: Binbin Wu Tested-by: Mikko Ylinen Acked-by: Kai Huang [Adjust userspace API. - Paolo] Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/tdx.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'arch/x86/kvm/vmx/tdx.c') diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 5d100c240ab3..b619a3478983 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1465,6 +1465,36 @@ static int tdx_get_td_vm_call_info(struct kvm_vcpu *vcpu) return 1; } +static int tdx_complete_simple(struct kvm_vcpu *vcpu) +{ + tdvmcall_set_return_code(vcpu, vcpu->run->tdx.unknown.ret); + return 1; +} + +static int tdx_get_quote(struct kvm_vcpu *vcpu) +{ + struct vcpu_tdx *tdx = to_tdx(vcpu); + u64 gpa = tdx->vp_enter_args.r12; + u64 size = tdx->vp_enter_args.r13; + + /* The gpa of buffer must have shared bit set. */ + if (vt_is_tdx_private_gpa(vcpu->kvm, gpa)) { + tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_INVALID_OPERAND); + return 1; + } + + vcpu->run->exit_reason = KVM_EXIT_TDX; + vcpu->run->tdx.flags = 0; + vcpu->run->tdx.nr = TDVMCALL_GET_QUOTE; + vcpu->run->tdx.get_quote.ret = TDVMCALL_STATUS_SUBFUNC_UNSUPPORTED; + vcpu->run->tdx.get_quote.gpa = gpa & ~gfn_to_gpa(kvm_gfn_direct_bits(tdx->vcpu.kvm)); + vcpu->run->tdx.get_quote.size = size; + + vcpu->arch.complete_userspace_io = tdx_complete_simple; + + return 0; +} + static int handle_tdvmcall(struct kvm_vcpu *vcpu) { switch (tdvmcall_leaf(vcpu)) { @@ -1474,6 +1504,8 @@ static int handle_tdvmcall(struct kvm_vcpu *vcpu) return tdx_report_fatal_error(vcpu); case TDVMCALL_GET_TD_VM_CALL_INFO: return tdx_get_td_vm_call_info(vcpu); + case TDVMCALL_GET_QUOTE: + return tdx_get_quote(vcpu); default: break; } -- cgit v1.2.3 From 25e8b1dd4883e6c251c3db5b347f3c8ae4ade921 Mon Sep 17 00:00:00 2001 From: Binbin Wu Date: Tue, 10 Jun 2025 10:14:21 +0800 Subject: KVM: TDX: Exit to userspace for GetTdVmCallInfo Exit to userspace for TDG.VP.VMCALL via KVM_EXIT_TDX, to allow userspace to provide information about the support of TDVMCALLs when r12 is 1 for the TDVMCALLs beyond the GHCI base API. GHCI spec defines the GHCI base TDVMCALLs: , , , , <#VE.RequestMMIO>, , , and . They must be supported by VMM to support TDX guests. For GetTdVmCallInfo - When leaf (r12) to enumerate TDVMCALL functionality is set to 0, successful execution indicates all GHCI base TDVMCALLs listed above are supported. Update the KVM TDX document with the set of the GHCI base APIs. - When leaf (r12) to enumerate TDVMCALL functionality is set to 1, it indicates the TDX guest is querying the supported TDVMCALLs beyond the GHCI base TDVMCALLs. Exit to userspace to let userspace set the TDVMCALL sub-function bit(s) accordingly to the leaf outputs. KVM could set the TDVMCALL bit(s) supported by itself when the TDVMCALLs don't need support from userspace after returning from userspace and before entering guest. Currently, no such TDVMCALLs implemented, KVM just sets the values returned from userspace. Suggested-by: Paolo Bonzini Signed-off-by: Binbin Wu [Adjust userspace API. - Paolo] Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/tdx.c | 43 +++++++++++++++++++++++++++++++++++++++---- 1 file changed, 39 insertions(+), 4 deletions(-) (limited to 'arch/x86/kvm/vmx/tdx.c') diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index b619a3478983..1ad20c273f3b 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1451,18 +1451,53 @@ error: return 1; } +static int tdx_complete_get_td_vm_call_info(struct kvm_vcpu *vcpu) +{ + struct vcpu_tdx *tdx = to_tdx(vcpu); + + tdvmcall_set_return_code(vcpu, vcpu->run->tdx.get_tdvmcall_info.ret); + + /* + * For now, there is no TDVMCALL beyond GHCI base API supported by KVM + * directly without the support from userspace, just set the value + * returned from userspace. + */ + tdx->vp_enter_args.r11 = vcpu->run->tdx.get_tdvmcall_info.r11; + tdx->vp_enter_args.r12 = vcpu->run->tdx.get_tdvmcall_info.r12; + tdx->vp_enter_args.r13 = vcpu->run->tdx.get_tdvmcall_info.r13; + tdx->vp_enter_args.r14 = vcpu->run->tdx.get_tdvmcall_info.r14; + + return 1; +} + static int tdx_get_td_vm_call_info(struct kvm_vcpu *vcpu) { struct vcpu_tdx *tdx = to_tdx(vcpu); - if (tdx->vp_enter_args.r12) - tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_INVALID_OPERAND); - else { + switch (tdx->vp_enter_args.r12) { + case 0: tdx->vp_enter_args.r11 = 0; + tdx->vp_enter_args.r12 = 0; tdx->vp_enter_args.r13 = 0; tdx->vp_enter_args.r14 = 0; + tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_SUCCESS); + return 1; + case 1: + vcpu->run->tdx.get_tdvmcall_info.leaf = tdx->vp_enter_args.r12; + vcpu->run->exit_reason = KVM_EXIT_TDX; + vcpu->run->tdx.flags = 0; + vcpu->run->tdx.nr = TDVMCALL_GET_TD_VM_CALL_INFO; + vcpu->run->tdx.get_tdvmcall_info.ret = TDVMCALL_STATUS_SUCCESS; + vcpu->run->tdx.get_tdvmcall_info.r11 = 0; + vcpu->run->tdx.get_tdvmcall_info.r12 = 0; + vcpu->run->tdx.get_tdvmcall_info.r13 = 0; + vcpu->run->tdx.get_tdvmcall_info.r14 = 0; + vcpu->arch.complete_userspace_io = tdx_complete_get_td_vm_call_info; + return 0; + default: + tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_INVALID_OPERAND); + return 1; } - return 1; } static int tdx_complete_simple(struct kvm_vcpu *vcpu) -- cgit v1.2.3