diff options
Diffstat (limited to 'arch/x86/coco/tdx/tdx.c')
| -rw-r--r-- | arch/x86/coco/tdx/tdx.c | 788 |
1 files changed, 788 insertions, 0 deletions
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c new file mode 100644 index 000000000000..b8998cf0508a --- /dev/null +++ b/arch/x86/coco/tdx/tdx.c @@ -0,0 +1,788 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (C) 2021-2022 Intel Corporation */ + +#undef pr_fmt +#define pr_fmt(fmt) "tdx: " fmt + +#include <linux/cpufeature.h> +#include <asm/coco.h> +#include <asm/tdx.h> +#include <asm/vmx.h> +#include <asm/insn.h> +#include <asm/insn-eval.h> +#include <asm/pgtable.h> + +/* 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<Instruction.HLT>. + * + * 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<Instruction.RDMSR>". + */ + 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<Instruction.WRMSR>". + */ + 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<Instruction.CPUID>". + */ + 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<Instruction.IO>". + */ + 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<Instruction.IO>". + */ + 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<MapGPA>" + */ + 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; +} + +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; + + x86_platform.guest.enc_cache_flush_required = tdx_cache_flush_required; + x86_platform.guest.enc_tlb_flush_required = tdx_tlb_flush_required; + x86_platform.guest.enc_status_change_finish = tdx_enc_status_changed; + + pr_info("Guest detected\n"); +} |