// SPDX-License-Identifier: GPL-2.0 /* Copyright (C) 2021-2022 Intel Corporation */ #undef pr_fmt #define pr_fmt(fmt) "tdx: " fmt #include #include #include #include #include #include #include /* TDX module Call Leaf IDs */ #define TDX_GET_INFO 1 #define TDX_GET_VEINFO 3 #define TDX_ACCEPT_PAGE 6 /* TDX hypercall Leaf IDs */ #define TDVMCALL_MAP_GPA 0x10001 /* MMIO direction */ #define EPT_READ 0 #define EPT_WRITE 1 /* Port I/O direction */ #define PORT_READ 0 #define PORT_WRITE 1 /* See Exit Qualification for I/O Instructions in VMX documentation */ #define VE_IS_IO_IN(e) ((e) & BIT(3)) #define VE_GET_IO_SIZE(e) (((e) & GENMASK(2, 0)) + 1) #define VE_GET_PORT_NUM(e) ((e) >> 16) #define VE_IS_IO_STRING(e) ((e) & BIT(4)) #define ATTR_SEPT_VE_DISABLE BIT(28) /* * Wrapper for standard use of __tdx_hypercall with no output aside from * return code. */ static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15) { struct tdx_hypercall_args args = { .r10 = TDX_HYPERCALL_STANDARD, .r11 = fn, .r12 = r12, .r13 = r13, .r14 = r14, .r15 = r15, }; return __tdx_hypercall(&args, 0); } /* Called from __tdx_hypercall() for unrecoverable failure */ void __tdx_hypercall_failed(void) { panic("TDVMCALL failed. TDX module bug?"); } /* * The TDG.VP.VMCALL-Instruction-execution sub-functions are defined * independently from but are currently matched 1:1 with VMX EXIT_REASONs. * Reusing the KVM EXIT_REASON macros makes it easier to connect the host and * guest sides of these calls. */ static u64 hcall_func(u64 exit_reason) { return exit_reason; } #ifdef CONFIG_KVM_GUEST long tdx_kvm_hypercall(unsigned int nr, unsigned long p1, unsigned long p2, unsigned long p3, unsigned long p4) { struct tdx_hypercall_args args = { .r10 = nr, .r11 = p1, .r12 = p2, .r13 = p3, .r14 = p4, }; return __tdx_hypercall(&args, 0); } EXPORT_SYMBOL_GPL(tdx_kvm_hypercall); #endif /* * Used for TDX guests to make calls directly to the TD module. This * should only be used for calls that have no legitimate reason to fail * or where the kernel can not survive the call failing. */ static inline void tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9, struct tdx_module_output *out) { if (__tdx_module_call(fn, rcx, rdx, r8, r9, out)) panic("TDCALL %lld failed (Buggy TDX module!)\n", fn); } static void tdx_parse_tdinfo(u64 *cc_mask) { struct tdx_module_output out; unsigned int gpa_width; u64 td_attr; /* * TDINFO TDX module call is used to get the TD execution environment * information like GPA width, number of available vcpus, debug mode * information, etc. More details about the ABI can be found in TDX * Guest-Host-Communication Interface (GHCI), section 2.4.2 TDCALL * [TDG.VP.INFO]. */ tdx_module_call(TDX_GET_INFO, 0, 0, 0, 0, &out); /* * The highest bit of a guest physical address is the "sharing" bit. * Set it for shared pages and clear it for private pages. * * The GPA width that comes out of this call is critical. TDX guests * can not meaningfully run without it. */ gpa_width = out.rcx & GENMASK(5, 0); *cc_mask = BIT_ULL(gpa_width - 1); /* * The kernel can not handle #VE's when accessing normal kernel * memory. Ensure that no #VE will be delivered for accesses to * TD-private memory. Only VMM-shared memory (MMIO) will #VE. */ td_attr = out.rdx; if (!(td_attr & ATTR_SEPT_VE_DISABLE)) panic("TD misconfiguration: SEPT_VE_DISABLE attibute must be set.\n"); } /* * The TDX module spec states that #VE may be injected for a limited set of * reasons: * * - Emulation of the architectural #VE injection on EPT violation; * * - As a result of guest TD execution of a disallowed instruction, * a disallowed MSR access, or CPUID virtualization; * * - A notification to the guest TD about anomalous behavior; * * The last one is opt-in and is not used by the kernel. * * The Intel Software Developer's Manual describes cases when instruction * length field can be used in section "Information for VM Exits Due to * Instruction Execution". * * For TDX, it ultimately means GET_VEINFO provides reliable instruction length * information if #VE occurred due to instruction execution, but not for EPT * violations. */ static int ve_instr_len(struct ve_info *ve) { switch (ve->exit_reason) { case EXIT_REASON_HLT: case EXIT_REASON_MSR_READ: case EXIT_REASON_MSR_WRITE: case EXIT_REASON_CPUID: case EXIT_REASON_IO_INSTRUCTION: /* It is safe to use ve->instr_len for #VE due instructions */ return ve->instr_len; case EXIT_REASON_EPT_VIOLATION: /* * For EPT violations, ve->insn_len is not defined. For those, * the kernel must decode instructions manually and should not * be using this function. */ WARN_ONCE(1, "ve->instr_len is not defined for EPT violations"); return 0; default: WARN_ONCE(1, "Unexpected #VE-type: %lld\n", ve->exit_reason); return ve->instr_len; } } static u64 __cpuidle __halt(const bool irq_disabled, const bool do_sti) { struct tdx_hypercall_args args = { .r10 = TDX_HYPERCALL_STANDARD, .r11 = hcall_func(EXIT_REASON_HLT), .r12 = irq_disabled, }; /* * Emulate HLT operation via hypercall. More info about ABI * can be found in TDX Guest-Host-Communication Interface * (GHCI), section 3.8 TDG.VP.VMCALL. * * The VMM uses the "IRQ disabled" param to understand IRQ * enabled status (RFLAGS.IF) of the TD guest and to determine * whether or not it should schedule the halted vCPU if an * IRQ becomes pending. E.g. if IRQs are disabled, the VMM * can keep the vCPU in virtual HLT, even if an IRQ is * pending, without hanging/breaking the guest. */ return __tdx_hypercall(&args, do_sti ? TDX_HCALL_ISSUE_STI : 0); } static int handle_halt(struct ve_info *ve) { /* * Since non safe halt is mainly used in CPU offlining * and the guest will always stay in the halt state, don't * call the STI instruction (set do_sti as false). */ const bool irq_disabled = irqs_disabled(); const bool do_sti = false; if (__halt(irq_disabled, do_sti)) return -EIO; return ve_instr_len(ve); } void __cpuidle tdx_safe_halt(void) { /* * For do_sti=true case, __tdx_hypercall() function enables * interrupts using the STI instruction before the TDCALL. So * set irq_disabled as false. */ const bool irq_disabled = false; const bool do_sti = true; /* * Use WARN_ONCE() to report the failure. */ if (__halt(irq_disabled, do_sti)) WARN_ONCE(1, "HLT instruction emulation failed\n"); } static int read_msr(struct pt_regs *regs, struct ve_info *ve) { struct tdx_hypercall_args args = { .r10 = TDX_HYPERCALL_STANDARD, .r11 = hcall_func(EXIT_REASON_MSR_READ), .r12 = regs->cx, }; /* * Emulate the MSR read via hypercall. More info about ABI * can be found in TDX Guest-Host-Communication Interface * (GHCI), section titled "TDG.VP.VMCALL". */ if (__tdx_hypercall(&args, TDX_HCALL_HAS_OUTPUT)) return -EIO; regs->ax = lower_32_bits(args.r11); regs->dx = upper_32_bits(args.r11); return ve_instr_len(ve); } static int write_msr(struct pt_regs *regs, struct ve_info *ve) { struct tdx_hypercall_args args = { .r10 = TDX_HYPERCALL_STANDARD, .r11 = hcall_func(EXIT_REASON_MSR_WRITE), .r12 = regs->cx, .r13 = (u64)regs->dx << 32 | regs->ax, }; /* * Emulate the MSR write via hypercall. More info about ABI * can be found in TDX Guest-Host-Communication Interface * (GHCI) section titled "TDG.VP.VMCALL". */ if (__tdx_hypercall(&args, 0)) return -EIO; return ve_instr_len(ve); } static int handle_cpuid(struct pt_regs *regs, struct ve_info *ve) { struct tdx_hypercall_args args = { .r10 = TDX_HYPERCALL_STANDARD, .r11 = hcall_func(EXIT_REASON_CPUID), .r12 = regs->ax, .r13 = regs->cx, }; /* * Only allow VMM to control range reserved for hypervisor * communication. * * Return all-zeros for any CPUID outside the range. It matches CPU * behaviour for non-supported leaf. */ if (regs->ax < 0x40000000 || regs->ax > 0x4FFFFFFF) { regs->ax = regs->bx = regs->cx = regs->dx = 0; return ve_instr_len(ve); } /* * Emulate the CPUID instruction via a hypercall. More info about * ABI can be found in TDX Guest-Host-Communication Interface * (GHCI), section titled "VP.VMCALL". */ if (__tdx_hypercall(&args, TDX_HCALL_HAS_OUTPUT)) return -EIO; /* * As per TDX GHCI CPUID ABI, r12-r15 registers contain contents of * EAX, EBX, ECX, EDX registers after the CPUID instruction execution. * So copy the register contents back to pt_regs. */ regs->ax = args.r12; regs->bx = args.r13; regs->cx = args.r14; regs->dx = args.r15; return ve_instr_len(ve); } static bool mmio_read(int size, unsigned long addr, unsigned long *val) { struct tdx_hypercall_args args = { .r10 = TDX_HYPERCALL_STANDARD, .r11 = hcall_func(EXIT_REASON_EPT_VIOLATION), .r12 = size, .r13 = EPT_READ, .r14 = addr, .r15 = *val, }; if (__tdx_hypercall(&args, TDX_HCALL_HAS_OUTPUT)) return false; *val = args.r11; return true; } static bool mmio_write(int size, unsigned long addr, unsigned long val) { return !_tdx_hypercall(hcall_func(EXIT_REASON_EPT_VIOLATION), size, EPT_WRITE, addr, val); } static int handle_mmio(struct pt_regs *regs, struct ve_info *ve) { unsigned long *reg, val, vaddr; char buffer[MAX_INSN_SIZE]; struct insn insn = {}; enum mmio_type mmio; int size, extend_size; u8 extend_val = 0; /* Only in-kernel MMIO is supported */ if (WARN_ON_ONCE(user_mode(regs))) return -EFAULT; if (copy_from_kernel_nofault(buffer, (void *)regs->ip, MAX_INSN_SIZE)) return -EFAULT; if (insn_decode(&insn, buffer, MAX_INSN_SIZE, INSN_MODE_64)) return -EINVAL; mmio = insn_decode_mmio(&insn, &size); if (WARN_ON_ONCE(mmio == MMIO_DECODE_FAILED)) return -EINVAL; if (mmio != MMIO_WRITE_IMM && mmio != MMIO_MOVS) { reg = insn_get_modrm_reg_ptr(&insn, regs); if (!reg) return -EINVAL; } /* * Reject EPT violation #VEs that split pages. * * MMIO accesses are supposed to be naturally aligned and therefore * never cross page boundaries. Seeing split page accesses indicates * a bug or a load_unaligned_zeropad() that stepped into an MMIO page. * * load_unaligned_zeropad() will recover using exception fixups. */ vaddr = (unsigned long)insn_get_addr_ref(&insn, regs); if (vaddr / PAGE_SIZE != (vaddr + size - 1) / PAGE_SIZE) return -EFAULT; /* Handle writes first */ switch (mmio) { case MMIO_WRITE: memcpy(&val, reg, size); if (!mmio_write(size, ve->gpa, val)) return -EIO; return insn.length; case MMIO_WRITE_IMM: val = insn.immediate.value; if (!mmio_write(size, ve->gpa, val)) return -EIO; return insn.length; case MMIO_READ: case MMIO_READ_ZERO_EXTEND: case MMIO_READ_SIGN_EXTEND: /* Reads are handled below */ break; case MMIO_MOVS: case MMIO_DECODE_FAILED: /* * MMIO was accessed with an instruction that could not be * decoded or handled properly. It was likely not using io.h * helpers or accessed MMIO accidentally. */ return -EINVAL; default: WARN_ONCE(1, "Unknown insn_decode_mmio() decode value?"); return -EINVAL; } /* Handle reads */ if (!mmio_read(size, ve->gpa, &val)) return -EIO; switch (mmio) { case MMIO_READ: /* Zero-extend for 32-bit operation */ extend_size = size == 4 ? sizeof(*reg) : 0; break; case MMIO_READ_ZERO_EXTEND: /* Zero extend based on operand size */ extend_size = insn.opnd_bytes; break; case MMIO_READ_SIGN_EXTEND: /* Sign extend based on operand size */ extend_size = insn.opnd_bytes; if (size == 1 && val & BIT(7)) extend_val = 0xFF; else if (size > 1 && val & BIT(15)) extend_val = 0xFF; break; default: /* All other cases has to be covered with the first switch() */ WARN_ON_ONCE(1); return -EINVAL; } if (extend_size) memset(reg, extend_val, extend_size); memcpy(reg, &val, size); return insn.length; } static bool handle_in(struct pt_regs *regs, int size, int port) { struct tdx_hypercall_args args = { .r10 = TDX_HYPERCALL_STANDARD, .r11 = hcall_func(EXIT_REASON_IO_INSTRUCTION), .r12 = size, .r13 = PORT_READ, .r14 = port, }; u64 mask = GENMASK(BITS_PER_BYTE * size, 0); bool success; /* * Emulate the I/O read via hypercall. More info about ABI can be found * in TDX Guest-Host-Communication Interface (GHCI) section titled * "TDG.VP.VMCALL". */ success = !__tdx_hypercall(&args, TDX_HCALL_HAS_OUTPUT); /* Update part of the register affected by the emulated instruction */ regs->ax &= ~mask; if (success) regs->ax |= args.r11 & mask; return success; } static bool handle_out(struct pt_regs *regs, int size, int port) { u64 mask = GENMASK(BITS_PER_BYTE * size, 0); /* * Emulate the I/O write via hypercall. More info about ABI can be found * in TDX Guest-Host-Communication Interface (GHCI) section titled * "TDG.VP.VMCALL". */ return !_tdx_hypercall(hcall_func(EXIT_REASON_IO_INSTRUCTION), size, PORT_WRITE, port, regs->ax & mask); } /* * Emulate I/O using hypercall. * * Assumes the IO instruction was using ax, which is enforced * by the standard io.h macros. * * Return True on success or False on failure. */ static int handle_io(struct pt_regs *regs, struct ve_info *ve) { u32 exit_qual = ve->exit_qual; int size, port; bool in, ret; if (VE_IS_IO_STRING(exit_qual)) return -EIO; in = VE_IS_IO_IN(exit_qual); size = VE_GET_IO_SIZE(exit_qual); port = VE_GET_PORT_NUM(exit_qual); if (in) ret = handle_in(regs, size, port); else ret = handle_out(regs, size, port); if (!ret) return -EIO; return ve_instr_len(ve); } /* * Early #VE exception handler. Only handles a subset of port I/O. * Intended only for earlyprintk. If failed, return false. */ __init bool tdx_early_handle_ve(struct pt_regs *regs) { struct ve_info ve; int insn_len; tdx_get_ve_info(&ve); if (ve.exit_reason != EXIT_REASON_IO_INSTRUCTION) return false; insn_len = handle_io(regs, &ve); if (insn_len < 0) return false; regs->ip += insn_len; return true; } void tdx_get_ve_info(struct ve_info *ve) { struct tdx_module_output out; /* * Called during #VE handling to retrieve the #VE info from the * TDX module. * * This has to be called early in #VE handling. A "nested" #VE which * occurs before this will raise a #DF and is not recoverable. * * The call retrieves the #VE info from the TDX module, which also * clears the "#VE valid" flag. This must be done before anything else * because any #VE that occurs while the valid flag is set will lead to * #DF. * * Note, the TDX module treats virtual NMIs as inhibited if the #VE * valid flag is set. It means that NMI=>#VE will not result in a #DF. */ tdx_module_call(TDX_GET_VEINFO, 0, 0, 0, 0, &out); /* Transfer the output parameters */ ve->exit_reason = out.rcx; ve->exit_qual = out.rdx; ve->gla = out.r8; ve->gpa = out.r9; ve->instr_len = lower_32_bits(out.r10); ve->instr_info = upper_32_bits(out.r10); } /* * Handle the user initiated #VE. * * On success, returns the number of bytes RIP should be incremented (>=0) * or -errno on error. */ static int virt_exception_user(struct pt_regs *regs, struct ve_info *ve) { switch (ve->exit_reason) { case EXIT_REASON_CPUID: return handle_cpuid(regs, ve); default: pr_warn("Unexpected #VE: %lld\n", ve->exit_reason); return -EIO; } } /* * Handle the kernel #VE. * * On success, returns the number of bytes RIP should be incremented (>=0) * or -errno on error. */ static int virt_exception_kernel(struct pt_regs *regs, struct ve_info *ve) { switch (ve->exit_reason) { case EXIT_REASON_HLT: return handle_halt(ve); case EXIT_REASON_MSR_READ: return read_msr(regs, ve); case EXIT_REASON_MSR_WRITE: return write_msr(regs, ve); case EXIT_REASON_CPUID: return handle_cpuid(regs, ve); case EXIT_REASON_EPT_VIOLATION: return handle_mmio(regs, ve); case EXIT_REASON_IO_INSTRUCTION: return handle_io(regs, ve); default: pr_warn("Unexpected #VE: %lld\n", ve->exit_reason); return -EIO; } } bool tdx_handle_virt_exception(struct pt_regs *regs, struct ve_info *ve) { int insn_len; if (user_mode(regs)) insn_len = virt_exception_user(regs, ve); else insn_len = virt_exception_kernel(regs, ve); if (insn_len < 0) return false; /* After successful #VE handling, move the IP */ regs->ip += insn_len; return true; } static bool tdx_tlb_flush_required(bool private) { /* * TDX guest is responsible for flushing TLB on private->shared * transition. VMM is responsible for flushing on shared->private. * * The VMM _can't_ flush private addresses as it can't generate PAs * with the guest's HKID. Shared memory isn't subject to integrity * checking, i.e. the VMM doesn't need to flush for its own protection. * * There's no need to flush when converting from shared to private, * as flushing is the VMM's responsibility in this case, e.g. it must * flush to avoid integrity failures in the face of a buggy or * malicious guest. */ return !private; } static bool tdx_cache_flush_required(void) { /* * AMD SME/SEV can avoid cache flushing if HW enforces cache coherence. * TDX doesn't have such capability. * * Flush cache unconditionally. */ return true; } static bool try_accept_one(phys_addr_t *start, unsigned long len, enum pg_level pg_level) { unsigned long accept_size = page_level_size(pg_level); u64 tdcall_rcx; u8 page_size; if (!IS_ALIGNED(*start, accept_size)) return false; if (len < accept_size) return false; /* * Pass the page physical address to the TDX module to accept the * pending, private page. * * Bits 2:0 of RCX encode page size: 0 - 4K, 1 - 2M, 2 - 1G. */ switch (pg_level) { case PG_LEVEL_4K: page_size = 0; break; case PG_LEVEL_2M: page_size = 1; break; case PG_LEVEL_1G: page_size = 2; break; default: return false; } tdcall_rcx = *start | page_size; if (__tdx_module_call(TDX_ACCEPT_PAGE, tdcall_rcx, 0, 0, 0, NULL)) return false; *start += accept_size; return true; } /* * Inform the VMM of the guest's intent for this physical page: shared with * the VMM or private to the guest. The VMM is expected to change its mapping * of the page in response. */ static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc) { phys_addr_t start = __pa(vaddr); phys_addr_t end = __pa(vaddr + numpages * PAGE_SIZE); if (!enc) { /* Set the shared (decrypted) bits: */ start |= cc_mkdec(0); end |= cc_mkdec(0); } /* * Notify the VMM about page mapping conversion. More info about ABI * can be found in TDX Guest-Host-Communication Interface (GHCI), * section "TDG.VP.VMCALL" */ if (_tdx_hypercall(TDVMCALL_MAP_GPA, start, end - start, 0, 0)) return false; /* private->shared conversion requires only MapGPA call */ if (!enc) return true; /* * For shared->private conversion, accept the page using * TDX_ACCEPT_PAGE TDX module call. */ while (start < end) { unsigned long len = end - start; /* * Try larger accepts first. It gives chance to VMM to keep * 1G/2M SEPT entries where possible and speeds up process by * cutting number of hypercalls (if successful). */ if (try_accept_one(&start, len, PG_LEVEL_1G)) continue; if (try_accept_one(&start, len, PG_LEVEL_2M)) continue; if (!try_accept_one(&start, len, PG_LEVEL_4K)) return false; } return true; } static bool tdx_enc_status_change_prepare(unsigned long vaddr, int numpages, bool enc) { /* * Only handle shared->private conversion here. * See the comment in tdx_early_init(). */ if (enc) return tdx_enc_status_changed(vaddr, numpages, enc); return true; } static bool tdx_enc_status_change_finish(unsigned long vaddr, int numpages, bool enc) { /* * Only handle private->shared conversion here. * See the comment in tdx_early_init(). */ if (!enc) return tdx_enc_status_changed(vaddr, numpages, enc); return true; } void __init tdx_early_init(void) { u64 cc_mask; u32 eax, sig[3]; cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax, &sig[0], &sig[2], &sig[1]); if (memcmp(TDX_IDENT, sig, sizeof(sig))) return; setup_force_cpu_cap(X86_FEATURE_TDX_GUEST); cc_set_vendor(CC_VENDOR_INTEL); tdx_parse_tdinfo(&cc_mask); cc_set_mask(cc_mask); /* * All bits above GPA width are reserved and kernel treats shared bit * as flag, not as part of physical address. * * Adjust physical mask to only cover valid GPA bits. */ physical_mask &= cc_mask - 1; /* * The kernel mapping should match the TDX metadata for the page. * load_unaligned_zeropad() can touch memory *adjacent* to that which is * owned by the caller and can catch even _momentary_ mismatches. Bad * things happen on mismatch: * * - Private mapping => Shared Page == Guest shutdown * - Shared mapping => Private Page == Recoverable #VE * * guest.enc_status_change_prepare() converts the page from * shared=>private before the mapping becomes private. * * guest.enc_status_change_finish() converts the page from * private=>shared after the mapping becomes private. * * In both cases there is a temporary shared mapping to a private page, * which can result in a #VE. But, there is never a private mapping to * a shared page. */ x86_platform.guest.enc_status_change_prepare = tdx_enc_status_change_prepare; x86_platform.guest.enc_status_change_finish = tdx_enc_status_change_finish; x86_platform.guest.enc_cache_flush_required = tdx_cache_flush_required; x86_platform.guest.enc_tlb_flush_required = tdx_tlb_flush_required; pr_info("Guest detected\n"); }