Add VMX exit handlers for SEAMCALL and TDCALL, and a SEAMCALL handler for TDX, to inject a #UD if a non-TD guest attempts to execute SEAMCALL or TDCALL, or if a TD guest attempst to execute SEAMCALL. Neither SEAMCALL nor TDCALL is gated by any software enablement other than VMXON, and so will generate a VM-Exit instead of e.g. a native #UD when executed from the guest kernel. Note! No unprivilege DoS of the L1 kernel is possible as TDCALL and SEAMCALL #GP at CPL > 0, and the CPL check is performed prior to the VMX non-root (VM-Exit) check, i.e. userspace can't crash the VM. And for a nested guest, KVM forwards unknown exits to L1, i.e. an L2 kernel can crash itself, but not L1. Note #2! The Intel® Trust Domain CPU Architectural Extensions spec's pseudocode shows the CPL > 0 check for SEAMCALL coming _after_ the VM-Exit, but that appears to be a documentation bug (likely because the CPL > 0 check was incorrectly bundled with other lower-priority #GP checks). Testing on SPR and EMR shows that the CPL > 0 check is performed before the VMX non-root check, i.e. SEAMCALL #GPs when executed in usermode. Note #3! The aforementioned Trust Domain spec uses confusing pseudocde that says that SEAMCALL will #UD if executed "inSEAM", but "inSEAM" specifically means in SEAM Root Mode, i.e. in the TDX-Module. The long- form description explicitly states that SEAMCALL generates an exit when executed in "SEAM VMX non-root operation". Cc: stable@vger.kernel.org Cc: Kai Huang Cc: Xiaoyao Li Cc: Rick Edgecombe Signed-off-by: Sean Christopherson --- arch/x86/include/uapi/asm/vmx.h | 1 + arch/x86/kvm/vmx/nested.c | 8 ++++++++ arch/x86/kvm/vmx/tdx.c | 3 +++ arch/x86/kvm/vmx/vmx.c | 8 ++++++++ 4 files changed, 20 insertions(+) diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h index 9792e329343e..1baa86dfe029 100644 --- a/arch/x86/include/uapi/asm/vmx.h +++ b/arch/x86/include/uapi/asm/vmx.h @@ -93,6 +93,7 @@ #define EXIT_REASON_TPAUSE 68 #define EXIT_REASON_BUS_LOCK 74 #define EXIT_REASON_NOTIFY 75 +#define EXIT_REASON_SEAMCALL 76 #define EXIT_REASON_TDCALL 77 #define EXIT_REASON_MSR_READ_IMM 84 #define EXIT_REASON_MSR_WRITE_IMM 85 diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 76271962cb70..f64a1eb241b6 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -6728,6 +6728,14 @@ static bool nested_vmx_l1_wants_exit(struct kvm_vcpu *vcpu, case EXIT_REASON_NOTIFY: /* Notify VM exit is not exposed to L1 */ return false; + case EXIT_REASON_SEAMCALL: + case EXIT_REASON_TDCALL: + /* + * SEAMCALL and TDCALL unconditionally VM-Exit, but aren't + * virtualized by KVM for L1 hypervisors, i.e. L1 should + * never want or expect such an exit. + */ + return true; default: return true; } diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 097304bf1e1d..7326c68f9909 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -2127,6 +2127,9 @@ int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath) return tdx_emulate_mmio(vcpu); case EXIT_REASON_EPT_VIOLATION: return tdx_handle_ept_violation(vcpu); + case EXIT_REASON_SEAMCALL: + kvm_queue_exception(vcpu, UD_VECTOR); + return 1; case EXIT_REASON_OTHER_SMI: /* * Unlike VMX, SMI in SEAM non-root mode (i.e. when diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 546272a5d34d..d1b34b7ca4a3 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6033,6 +6033,12 @@ static int handle_vmx_instruction(struct kvm_vcpu *vcpu) return 1; } +static int handle_tdx_instruction(struct kvm_vcpu *vcpu) +{ + kvm_queue_exception(vcpu, UD_VECTOR); + return 1; +} + #ifndef CONFIG_X86_SGX_KVM static int handle_encls(struct kvm_vcpu *vcpu) { @@ -6158,6 +6164,8 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = { [EXIT_REASON_ENCLS] = handle_encls, [EXIT_REASON_BUS_LOCK] = handle_bus_lock_vmexit, [EXIT_REASON_NOTIFY] = handle_notify, + [EXIT_REASON_SEAMCALL] = handle_tdx_instruction, + [EXIT_REASON_TDCALL] = handle_tdx_instruction, [EXIT_REASON_MSR_READ_IMM] = handle_rdmsr_imm, [EXIT_REASON_MSR_WRITE_IMM] = handle_wrmsr_imm, }; base-commit: 6b36119b94d0b2bb8cea9d512017efafd461d6ac -- 2.51.0.788.g6d19910ace-goog