1// SPDX-License-Identifier: GPL-2.0
2/* Copyright (C) 2021-2022 Intel Corporation */
3
4#undef pr_fmt
5#define pr_fmt(fmt) "tdx: " fmt
6
7#include <linux/cpufeature.h>
8#include <linux/export.h>
9#include <linux/io.h>
10#include <asm/coco.h>
11#include <asm/tdx.h>
12#include <asm/vmx.h>
13#include <asm/ia32.h>
14#include <asm/insn.h>
15#include <asm/insn-eval.h>
16#include <asm/pgtable.h>
17
18/* MMIO direction */
19#define EPT_READ 0
20#define EPT_WRITE 1
21
22/* Port I/O direction */
23#define PORT_READ 0
24#define PORT_WRITE 1
25
26/* See Exit Qualification for I/O Instructions in VMX documentation */
27#define VE_IS_IO_IN(e) ((e) & BIT(3))
28#define VE_GET_IO_SIZE(e) (((e) & GENMASK(2, 0)) + 1)
29#define VE_GET_PORT_NUM(e) ((e) >> 16)
30#define VE_IS_IO_STRING(e) ((e) & BIT(4))
31
32#define ATTR_DEBUG BIT(0)
33#define ATTR_SEPT_VE_DISABLE BIT(28)
34
35/* TDX Module call error codes */
36#define TDCALL_RETURN_CODE(a) ((a) >> 32)
37#define TDCALL_INVALID_OPERAND 0xc0000100
38
39#define TDREPORT_SUBTYPE_0 0
40
41/* Called from __tdx_hypercall() for unrecoverable failure */
42noinstr void __noreturn __tdx_hypercall_failed(void)
43{
44 instrumentation_begin();
45 panic(fmt: "TDVMCALL failed. TDX module bug?");
46}
47
48#ifdef CONFIG_KVM_GUEST
49long tdx_kvm_hypercall(unsigned int nr, unsigned long p1, unsigned long p2,
50 unsigned long p3, unsigned long p4)
51{
52 struct tdx_module_args args = {
53 .r10 = nr,
54 .r11 = p1,
55 .r12 = p2,
56 .r13 = p3,
57 .r14 = p4,
58 };
59
60 return __tdx_hypercall(args: &args);
61}
62EXPORT_SYMBOL_GPL(tdx_kvm_hypercall);
63#endif
64
65/*
66 * Used for TDX guests to make calls directly to the TD module. This
67 * should only be used for calls that have no legitimate reason to fail
68 * or where the kernel can not survive the call failing.
69 */
70static inline void tdcall(u64 fn, struct tdx_module_args *args)
71{
72 if (__tdcall_ret(fn, args))
73 panic(fmt: "TDCALL %lld failed (Buggy TDX module!)\n", fn);
74}
75
76/**
77 * tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
78 * subtype 0) using TDG.MR.REPORT TDCALL.
79 * @reportdata: Address of the input buffer which contains user-defined
80 * REPORTDATA to be included into TDREPORT.
81 * @tdreport: Address of the output buffer to store TDREPORT.
82 *
83 * Refer to section titled "TDG.MR.REPORT leaf" in the TDX Module
84 * v1.0 specification for more information on TDG.MR.REPORT TDCALL.
85 * It is used in the TDX guest driver module to get the TDREPORT0.
86 *
87 * Return 0 on success, -EINVAL for invalid operands, or -EIO on
88 * other TDCALL failures.
89 */
90int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
91{
92 struct tdx_module_args args = {
93 .rcx = virt_to_phys(address: tdreport),
94 .rdx = virt_to_phys(address: reportdata),
95 .r8 = TDREPORT_SUBTYPE_0,
96 };
97 u64 ret;
98
99 ret = __tdcall(TDG_MR_REPORT, args: &args);
100 if (ret) {
101 if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
102 return -EINVAL;
103 return -EIO;
104 }
105
106 return 0;
107}
108EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);
109
110/**
111 * tdx_hcall_get_quote() - Wrapper to request TD Quote using GetQuote
112 * hypercall.
113 * @buf: Address of the directly mapped shared kernel buffer which
114 * contains TDREPORT. The same buffer will be used by VMM to
115 * store the generated TD Quote output.
116 * @size: size of the tdquote buffer (4KB-aligned).
117 *
118 * Refer to section titled "TDG.VP.VMCALL<GetQuote>" in the TDX GHCI
119 * v1.0 specification for more information on GetQuote hypercall.
120 * It is used in the TDX guest driver module to get the TD Quote.
121 *
122 * Return 0 on success or error code on failure.
123 */
124u64 tdx_hcall_get_quote(u8 *buf, size_t size)
125{
126 /* Since buf is a shared memory, set the shared (decrypted) bits */
127 return _tdx_hypercall(TDVMCALL_GET_QUOTE, r12: cc_mkdec(virt_to_phys(address: buf)), r13: size, r14: 0, r15: 0);
128}
129EXPORT_SYMBOL_GPL(tdx_hcall_get_quote);
130
131static void __noreturn tdx_panic(const char *msg)
132{
133 struct tdx_module_args args = {
134 .r10 = TDX_HYPERCALL_STANDARD,
135 .r11 = TDVMCALL_REPORT_FATAL_ERROR,
136 .r12 = 0, /* Error code: 0 is Panic */
137 };
138 union {
139 /* Define register order according to the GHCI */
140 struct { u64 r14, r15, rbx, rdi, rsi, r8, r9, rdx; };
141
142 char str[64];
143 } message;
144
145 /* VMM assumes '\0' in byte 65, if the message took all 64 bytes */
146 strtomem_pad(message.str, msg, '\0');
147
148 args.r8 = message.r8;
149 args.r9 = message.r9;
150 args.r14 = message.r14;
151 args.r15 = message.r15;
152 args.rdi = message.rdi;
153 args.rsi = message.rsi;
154 args.rbx = message.rbx;
155 args.rdx = message.rdx;
156
157 /*
158 * This hypercall should never return and it is not safe
159 * to keep the guest running. Call it forever if it
160 * happens to return.
161 */
162 while (1)
163 __tdx_hypercall(args: &args);
164}
165
166static void tdx_parse_tdinfo(u64 *cc_mask)
167{
168 struct tdx_module_args args = {};
169 unsigned int gpa_width;
170 u64 td_attr;
171
172 /*
173 * TDINFO TDX module call is used to get the TD execution environment
174 * information like GPA width, number of available vcpus, debug mode
175 * information, etc. More details about the ABI can be found in TDX
176 * Guest-Host-Communication Interface (GHCI), section 2.4.2 TDCALL
177 * [TDG.VP.INFO].
178 */
179 tdcall(TDG_VP_INFO, args: &args);
180
181 /*
182 * The highest bit of a guest physical address is the "sharing" bit.
183 * Set it for shared pages and clear it for private pages.
184 *
185 * The GPA width that comes out of this call is critical. TDX guests
186 * can not meaningfully run without it.
187 */
188 gpa_width = args.rcx & GENMASK(5, 0);
189 *cc_mask = BIT_ULL(gpa_width - 1);
190
191 /*
192 * The kernel can not handle #VE's when accessing normal kernel
193 * memory. Ensure that no #VE will be delivered for accesses to
194 * TD-private memory. Only VMM-shared memory (MMIO) will #VE.
195 */
196 td_attr = args.rdx;
197 if (!(td_attr & ATTR_SEPT_VE_DISABLE)) {
198 const char *msg = "TD misconfiguration: SEPT_VE_DISABLE attribute must be set.";
199
200 /* Relax SEPT_VE_DISABLE check for debug TD. */
201 if (td_attr & ATTR_DEBUG)
202 pr_warn("%s\n", msg);
203 else
204 tdx_panic(msg);
205 }
206}
207
208/*
209 * The TDX module spec states that #VE may be injected for a limited set of
210 * reasons:
211 *
212 * - Emulation of the architectural #VE injection on EPT violation;
213 *
214 * - As a result of guest TD execution of a disallowed instruction,
215 * a disallowed MSR access, or CPUID virtualization;
216 *
217 * - A notification to the guest TD about anomalous behavior;
218 *
219 * The last one is opt-in and is not used by the kernel.
220 *
221 * The Intel Software Developer's Manual describes cases when instruction
222 * length field can be used in section "Information for VM Exits Due to
223 * Instruction Execution".
224 *
225 * For TDX, it ultimately means GET_VEINFO provides reliable instruction length
226 * information if #VE occurred due to instruction execution, but not for EPT
227 * violations.
228 */
229static int ve_instr_len(struct ve_info *ve)
230{
231 switch (ve->exit_reason) {
232 case EXIT_REASON_HLT:
233 case EXIT_REASON_MSR_READ:
234 case EXIT_REASON_MSR_WRITE:
235 case EXIT_REASON_CPUID:
236 case EXIT_REASON_IO_INSTRUCTION:
237 /* It is safe to use ve->instr_len for #VE due instructions */
238 return ve->instr_len;
239 case EXIT_REASON_EPT_VIOLATION:
240 /*
241 * For EPT violations, ve->insn_len is not defined. For those,
242 * the kernel must decode instructions manually and should not
243 * be using this function.
244 */
245 WARN_ONCE(1, "ve->instr_len is not defined for EPT violations");
246 return 0;
247 default:
248 WARN_ONCE(1, "Unexpected #VE-type: %lld\n", ve->exit_reason);
249 return ve->instr_len;
250 }
251}
252
253static u64 __cpuidle __halt(const bool irq_disabled)
254{
255 struct tdx_module_args args = {
256 .r10 = TDX_HYPERCALL_STANDARD,
257 .r11 = hcall_func(EXIT_REASON_HLT),
258 .r12 = irq_disabled,
259 };
260
261 /*
262 * Emulate HLT operation via hypercall. More info about ABI
263 * can be found in TDX Guest-Host-Communication Interface
264 * (GHCI), section 3.8 TDG.VP.VMCALL<Instruction.HLT>.
265 *
266 * The VMM uses the "IRQ disabled" param to understand IRQ
267 * enabled status (RFLAGS.IF) of the TD guest and to determine
268 * whether or not it should schedule the halted vCPU if an
269 * IRQ becomes pending. E.g. if IRQs are disabled, the VMM
270 * can keep the vCPU in virtual HLT, even if an IRQ is
271 * pending, without hanging/breaking the guest.
272 */
273 return __tdx_hypercall(args: &args);
274}
275
276static int handle_halt(struct ve_info *ve)
277{
278 const bool irq_disabled = irqs_disabled();
279
280 if (__halt(irq_disabled))
281 return -EIO;
282
283 return ve_instr_len(ve);
284}
285
286void __cpuidle tdx_safe_halt(void)
287{
288 const bool irq_disabled = false;
289
290 /*
291 * Use WARN_ONCE() to report the failure.
292 */
293 if (__halt(irq_disabled))
294 WARN_ONCE(1, "HLT instruction emulation failed\n");
295}
296
297static int read_msr(struct pt_regs *regs, struct ve_info *ve)
298{
299 struct tdx_module_args args = {
300 .r10 = TDX_HYPERCALL_STANDARD,
301 .r11 = hcall_func(EXIT_REASON_MSR_READ),
302 .r12 = regs->cx,
303 };
304
305 /*
306 * Emulate the MSR read via hypercall. More info about ABI
307 * can be found in TDX Guest-Host-Communication Interface
308 * (GHCI), section titled "TDG.VP.VMCALL<Instruction.RDMSR>".
309 */
310 if (__tdx_hypercall(args: &args))
311 return -EIO;
312
313 regs->ax = lower_32_bits(args.r11);
314 regs->dx = upper_32_bits(args.r11);
315 return ve_instr_len(ve);
316}
317
318static int write_msr(struct pt_regs *regs, struct ve_info *ve)
319{
320 struct tdx_module_args args = {
321 .r10 = TDX_HYPERCALL_STANDARD,
322 .r11 = hcall_func(EXIT_REASON_MSR_WRITE),
323 .r12 = regs->cx,
324 .r13 = (u64)regs->dx << 32 | regs->ax,
325 };
326
327 /*
328 * Emulate the MSR write via hypercall. More info about ABI
329 * can be found in TDX Guest-Host-Communication Interface
330 * (GHCI) section titled "TDG.VP.VMCALL<Instruction.WRMSR>".
331 */
332 if (__tdx_hypercall(args: &args))
333 return -EIO;
334
335 return ve_instr_len(ve);
336}
337
338static int handle_cpuid(struct pt_regs *regs, struct ve_info *ve)
339{
340 struct tdx_module_args args = {
341 .r10 = TDX_HYPERCALL_STANDARD,
342 .r11 = hcall_func(EXIT_REASON_CPUID),
343 .r12 = regs->ax,
344 .r13 = regs->cx,
345 };
346
347 /*
348 * Only allow VMM to control range reserved for hypervisor
349 * communication.
350 *
351 * Return all-zeros for any CPUID outside the range. It matches CPU
352 * behaviour for non-supported leaf.
353 */
354 if (regs->ax < 0x40000000 || regs->ax > 0x4FFFFFFF) {
355 regs->ax = regs->bx = regs->cx = regs->dx = 0;
356 return ve_instr_len(ve);
357 }
358
359 /*
360 * Emulate the CPUID instruction via a hypercall. More info about
361 * ABI can be found in TDX Guest-Host-Communication Interface
362 * (GHCI), section titled "VP.VMCALL<Instruction.CPUID>".
363 */
364 if (__tdx_hypercall(args: &args))
365 return -EIO;
366
367 /*
368 * As per TDX GHCI CPUID ABI, r12-r15 registers contain contents of
369 * EAX, EBX, ECX, EDX registers after the CPUID instruction execution.
370 * So copy the register contents back to pt_regs.
371 */
372 regs->ax = args.r12;
373 regs->bx = args.r13;
374 regs->cx = args.r14;
375 regs->dx = args.r15;
376
377 return ve_instr_len(ve);
378}
379
380static bool mmio_read(int size, unsigned long addr, unsigned long *val)
381{
382 struct tdx_module_args args = {
383 .r10 = TDX_HYPERCALL_STANDARD,
384 .r11 = hcall_func(EXIT_REASON_EPT_VIOLATION),
385 .r12 = size,
386 .r13 = EPT_READ,
387 .r14 = addr,
388 .r15 = *val,
389 };
390
391 if (__tdx_hypercall(args: &args))
392 return false;
393
394 *val = args.r11;
395 return true;
396}
397
398static bool mmio_write(int size, unsigned long addr, unsigned long val)
399{
400 return !_tdx_hypercall(fn: hcall_func(EXIT_REASON_EPT_VIOLATION), r12: size,
401 EPT_WRITE, r14: addr, r15: val);
402}
403
404static int handle_mmio(struct pt_regs *regs, struct ve_info *ve)
405{
406 unsigned long *reg, val, vaddr;
407 char buffer[MAX_INSN_SIZE];
408 enum insn_mmio_type mmio;
409 struct insn insn = {};
410 int size, extend_size;
411 u8 extend_val = 0;
412
413 /* Only in-kernel MMIO is supported */
414 if (WARN_ON_ONCE(user_mode(regs)))
415 return -EFAULT;
416
417 if (copy_from_kernel_nofault(dst: buffer, src: (void *)regs->ip, MAX_INSN_SIZE))
418 return -EFAULT;
419
420 if (insn_decode(insn: &insn, kaddr: buffer, MAX_INSN_SIZE, m: INSN_MODE_64))
421 return -EINVAL;
422
423 mmio = insn_decode_mmio(insn: &insn, bytes: &size);
424 if (WARN_ON_ONCE(mmio == INSN_MMIO_DECODE_FAILED))
425 return -EINVAL;
426
427 if (mmio != INSN_MMIO_WRITE_IMM && mmio != INSN_MMIO_MOVS) {
428 reg = insn_get_modrm_reg_ptr(insn: &insn, regs);
429 if (!reg)
430 return -EINVAL;
431 }
432
433 /*
434 * Reject EPT violation #VEs that split pages.
435 *
436 * MMIO accesses are supposed to be naturally aligned and therefore
437 * never cross page boundaries. Seeing split page accesses indicates
438 * a bug or a load_unaligned_zeropad() that stepped into an MMIO page.
439 *
440 * load_unaligned_zeropad() will recover using exception fixups.
441 */
442 vaddr = (unsigned long)insn_get_addr_ref(insn: &insn, regs);
443 if (vaddr / PAGE_SIZE != (vaddr + size - 1) / PAGE_SIZE)
444 return -EFAULT;
445
446 /* Handle writes first */
447 switch (mmio) {
448 case INSN_MMIO_WRITE:
449 memcpy(&val, reg, size);
450 if (!mmio_write(size, addr: ve->gpa, val))
451 return -EIO;
452 return insn.length;
453 case INSN_MMIO_WRITE_IMM:
454 val = insn.immediate.value;
455 if (!mmio_write(size, addr: ve->gpa, val))
456 return -EIO;
457 return insn.length;
458 case INSN_MMIO_READ:
459 case INSN_MMIO_READ_ZERO_EXTEND:
460 case INSN_MMIO_READ_SIGN_EXTEND:
461 /* Reads are handled below */
462 break;
463 case INSN_MMIO_MOVS:
464 case INSN_MMIO_DECODE_FAILED:
465 /*
466 * MMIO was accessed with an instruction that could not be
467 * decoded or handled properly. It was likely not using io.h
468 * helpers or accessed MMIO accidentally.
469 */
470 return -EINVAL;
471 default:
472 WARN_ONCE(1, "Unknown insn_decode_mmio() decode value?");
473 return -EINVAL;
474 }
475
476 /* Handle reads */
477 if (!mmio_read(size, addr: ve->gpa, val: &val))
478 return -EIO;
479
480 switch (mmio) {
481 case INSN_MMIO_READ:
482 /* Zero-extend for 32-bit operation */
483 extend_size = size == 4 ? sizeof(*reg) : 0;
484 break;
485 case INSN_MMIO_READ_ZERO_EXTEND:
486 /* Zero extend based on operand size */
487 extend_size = insn.opnd_bytes;
488 break;
489 case INSN_MMIO_READ_SIGN_EXTEND:
490 /* Sign extend based on operand size */
491 extend_size = insn.opnd_bytes;
492 if (size == 1 && val & BIT(7))
493 extend_val = 0xFF;
494 else if (size > 1 && val & BIT(15))
495 extend_val = 0xFF;
496 break;
497 default:
498 /* All other cases has to be covered with the first switch() */
499 WARN_ON_ONCE(1);
500 return -EINVAL;
501 }
502
503 if (extend_size)
504 memset(reg, extend_val, extend_size);
505 memcpy(reg, &val, size);
506 return insn.length;
507}
508
509static bool handle_in(struct pt_regs *regs, int size, int port)
510{
511 struct tdx_module_args args = {
512 .r10 = TDX_HYPERCALL_STANDARD,
513 .r11 = hcall_func(EXIT_REASON_IO_INSTRUCTION),
514 .r12 = size,
515 .r13 = PORT_READ,
516 .r14 = port,
517 };
518 u64 mask = GENMASK(BITS_PER_BYTE * size, 0);
519 bool success;
520
521 /*
522 * Emulate the I/O read via hypercall. More info about ABI can be found
523 * in TDX Guest-Host-Communication Interface (GHCI) section titled
524 * "TDG.VP.VMCALL<Instruction.IO>".
525 */
526 success = !__tdx_hypercall(args: &args);
527
528 /* Update part of the register affected by the emulated instruction */
529 regs->ax &= ~mask;
530 if (success)
531 regs->ax |= args.r11 & mask;
532
533 return success;
534}
535
536static bool handle_out(struct pt_regs *regs, int size, int port)
537{
538 u64 mask = GENMASK(BITS_PER_BYTE * size, 0);
539
540 /*
541 * Emulate the I/O write via hypercall. More info about ABI can be found
542 * in TDX Guest-Host-Communication Interface (GHCI) section titled
543 * "TDG.VP.VMCALL<Instruction.IO>".
544 */
545 return !_tdx_hypercall(fn: hcall_func(EXIT_REASON_IO_INSTRUCTION), r12: size,
546 PORT_WRITE, r14: port, r15: regs->ax & mask);
547}
548
549/*
550 * Emulate I/O using hypercall.
551 *
552 * Assumes the IO instruction was using ax, which is enforced
553 * by the standard io.h macros.
554 *
555 * Return True on success or False on failure.
556 */
557static int handle_io(struct pt_regs *regs, struct ve_info *ve)
558{
559 u32 exit_qual = ve->exit_qual;
560 int size, port;
561 bool in, ret;
562
563 if (VE_IS_IO_STRING(exit_qual))
564 return -EIO;
565
566 in = VE_IS_IO_IN(exit_qual);
567 size = VE_GET_IO_SIZE(exit_qual);
568 port = VE_GET_PORT_NUM(exit_qual);
569
570
571 if (in)
572 ret = handle_in(regs, size, port);
573 else
574 ret = handle_out(regs, size, port);
575 if (!ret)
576 return -EIO;
577
578 return ve_instr_len(ve);
579}
580
581/*
582 * Early #VE exception handler. Only handles a subset of port I/O.
583 * Intended only for earlyprintk. If failed, return false.
584 */
585__init bool tdx_early_handle_ve(struct pt_regs *regs)
586{
587 struct ve_info ve;
588 int insn_len;
589
590 tdx_get_ve_info(ve: &ve);
591
592 if (ve.exit_reason != EXIT_REASON_IO_INSTRUCTION)
593 return false;
594
595 insn_len = handle_io(regs, ve: &ve);
596 if (insn_len < 0)
597 return false;
598
599 regs->ip += insn_len;
600 return true;
601}
602
603void tdx_get_ve_info(struct ve_info *ve)
604{
605 struct tdx_module_args args = {};
606
607 /*
608 * Called during #VE handling to retrieve the #VE info from the
609 * TDX module.
610 *
611 * This has to be called early in #VE handling. A "nested" #VE which
612 * occurs before this will raise a #DF and is not recoverable.
613 *
614 * The call retrieves the #VE info from the TDX module, which also
615 * clears the "#VE valid" flag. This must be done before anything else
616 * because any #VE that occurs while the valid flag is set will lead to
617 * #DF.
618 *
619 * Note, the TDX module treats virtual NMIs as inhibited if the #VE
620 * valid flag is set. It means that NMI=>#VE will not result in a #DF.
621 */
622 tdcall(TDG_VP_VEINFO_GET, args: &args);
623
624 /* Transfer the output parameters */
625 ve->exit_reason = args.rcx;
626 ve->exit_qual = args.rdx;
627 ve->gla = args.r8;
628 ve->gpa = args.r9;
629 ve->instr_len = lower_32_bits(args.r10);
630 ve->instr_info = upper_32_bits(args.r10);
631}
632
633/*
634 * Handle the user initiated #VE.
635 *
636 * On success, returns the number of bytes RIP should be incremented (>=0)
637 * or -errno on error.
638 */
639static int virt_exception_user(struct pt_regs *regs, struct ve_info *ve)
640{
641 switch (ve->exit_reason) {
642 case EXIT_REASON_CPUID:
643 return handle_cpuid(regs, ve);
644 default:
645 pr_warn("Unexpected #VE: %lld\n", ve->exit_reason);
646 return -EIO;
647 }
648}
649
650static inline bool is_private_gpa(u64 gpa)
651{
652 return gpa == cc_mkenc(val: gpa);
653}
654
655/*
656 * Handle the kernel #VE.
657 *
658 * On success, returns the number of bytes RIP should be incremented (>=0)
659 * or -errno on error.
660 */
661static int virt_exception_kernel(struct pt_regs *regs, struct ve_info *ve)
662{
663 switch (ve->exit_reason) {
664 case EXIT_REASON_HLT:
665 return handle_halt(ve);
666 case EXIT_REASON_MSR_READ:
667 return read_msr(regs, ve);
668 case EXIT_REASON_MSR_WRITE:
669 return write_msr(regs, ve);
670 case EXIT_REASON_CPUID:
671 return handle_cpuid(regs, ve);
672 case EXIT_REASON_EPT_VIOLATION:
673 if (is_private_gpa(gpa: ve->gpa))
674 panic(fmt: "Unexpected EPT-violation on private memory.");
675 return handle_mmio(regs, ve);
676 case EXIT_REASON_IO_INSTRUCTION:
677 return handle_io(regs, ve);
678 default:
679 pr_warn("Unexpected #VE: %lld\n", ve->exit_reason);
680 return -EIO;
681 }
682}
683
684bool tdx_handle_virt_exception(struct pt_regs *regs, struct ve_info *ve)
685{
686 int insn_len;
687
688 if (user_mode(regs))
689 insn_len = virt_exception_user(regs, ve);
690 else
691 insn_len = virt_exception_kernel(regs, ve);
692 if (insn_len < 0)
693 return false;
694
695 /* After successful #VE handling, move the IP */
696 regs->ip += insn_len;
697
698 return true;
699}
700
701static bool tdx_tlb_flush_required(bool private)
702{
703 /*
704 * TDX guest is responsible for flushing TLB on private->shared
705 * transition. VMM is responsible for flushing on shared->private.
706 *
707 * The VMM _can't_ flush private addresses as it can't generate PAs
708 * with the guest's HKID. Shared memory isn't subject to integrity
709 * checking, i.e. the VMM doesn't need to flush for its own protection.
710 *
711 * There's no need to flush when converting from shared to private,
712 * as flushing is the VMM's responsibility in this case, e.g. it must
713 * flush to avoid integrity failures in the face of a buggy or
714 * malicious guest.
715 */
716 return !private;
717}
718
719static bool tdx_cache_flush_required(void)
720{
721 /*
722 * AMD SME/SEV can avoid cache flushing if HW enforces cache coherence.
723 * TDX doesn't have such capability.
724 *
725 * Flush cache unconditionally.
726 */
727 return true;
728}
729
730/*
731 * Notify the VMM about page mapping conversion. More info about ABI
732 * can be found in TDX Guest-Host-Communication Interface (GHCI),
733 * section "TDG.VP.VMCALL<MapGPA>".
734 */
735static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
736{
737 /* Retrying the hypercall a second time should succeed; use 3 just in case */
738 const int max_retries_per_page = 3;
739 int retry_count = 0;
740
741 if (!enc) {
742 /* Set the shared (decrypted) bits: */
743 start |= cc_mkdec(val: 0);
744 end |= cc_mkdec(val: 0);
745 }
746
747 while (retry_count < max_retries_per_page) {
748 struct tdx_module_args args = {
749 .r10 = TDX_HYPERCALL_STANDARD,
750 .r11 = TDVMCALL_MAP_GPA,
751 .r12 = start,
752 .r13 = end - start };
753
754 u64 map_fail_paddr;
755 u64 ret = __tdx_hypercall(args: &args);
756
757 if (ret != TDVMCALL_STATUS_RETRY)
758 return !ret;
759 /*
760 * The guest must retry the operation for the pages in the
761 * region starting at the GPA specified in R11. R11 comes
762 * from the untrusted VMM. Sanity check it.
763 */
764 map_fail_paddr = args.r11;
765 if (map_fail_paddr < start || map_fail_paddr >= end)
766 return false;
767
768 /* "Consume" a retry without forward progress */
769 if (map_fail_paddr == start) {
770 retry_count++;
771 continue;
772 }
773
774 start = map_fail_paddr;
775 retry_count = 0;
776 }
777
778 return false;
779}
780
781/*
782 * Inform the VMM of the guest's intent for this physical page: shared with
783 * the VMM or private to the guest. The VMM is expected to change its mapping
784 * of the page in response.
785 */
786static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
787{
788 phys_addr_t start = __pa(vaddr);
789 phys_addr_t end = __pa(vaddr + numpages * PAGE_SIZE);
790
791 if (!tdx_map_gpa(start, end, enc))
792 return false;
793
794 /* shared->private conversion requires memory to be accepted before use */
795 if (enc)
796 return tdx_accept_memory(start, end);
797
798 return true;
799}
800
801static bool tdx_enc_status_change_prepare(unsigned long vaddr, int numpages,
802 bool enc)
803{
804 /*
805 * Only handle shared->private conversion here.
806 * See the comment in tdx_early_init().
807 */
808 if (enc)
809 return tdx_enc_status_changed(vaddr, numpages, enc);
810 return true;
811}
812
813static bool tdx_enc_status_change_finish(unsigned long vaddr, int numpages,
814 bool enc)
815{
816 /*
817 * Only handle private->shared conversion here.
818 * See the comment in tdx_early_init().
819 */
820 if (!enc)
821 return tdx_enc_status_changed(vaddr, numpages, enc);
822 return true;
823}
824
825void __init tdx_early_init(void)
826{
827 struct tdx_module_args args = {
828 .rdx = TDCS_NOTIFY_ENABLES,
829 .r9 = -1ULL,
830 };
831 u64 cc_mask;
832 u32 eax, sig[3];
833
834 cpuid_count(TDX_CPUID_LEAF_ID, count: 0, eax: &eax, ebx: &sig[0], ecx: &sig[2], edx: &sig[1]);
835
836 if (memcmp(TDX_IDENT, q: sig, size: sizeof(sig)))
837 return;
838
839 setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
840
841 /* TSC is the only reliable clock in TDX guest */
842 setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
843
844 cc_vendor = CC_VENDOR_INTEL;
845 tdx_parse_tdinfo(cc_mask: &cc_mask);
846 cc_set_mask(mask: cc_mask);
847
848 /* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
849 tdcall(TDG_VM_WR, args: &args);
850
851 /*
852 * All bits above GPA width are reserved and kernel treats shared bit
853 * as flag, not as part of physical address.
854 *
855 * Adjust physical mask to only cover valid GPA bits.
856 */
857 physical_mask &= cc_mask - 1;
858
859 /*
860 * The kernel mapping should match the TDX metadata for the page.
861 * load_unaligned_zeropad() can touch memory *adjacent* to that which is
862 * owned by the caller and can catch even _momentary_ mismatches. Bad
863 * things happen on mismatch:
864 *
865 * - Private mapping => Shared Page == Guest shutdown
866 * - Shared mapping => Private Page == Recoverable #VE
867 *
868 * guest.enc_status_change_prepare() converts the page from
869 * shared=>private before the mapping becomes private.
870 *
871 * guest.enc_status_change_finish() converts the page from
872 * private=>shared after the mapping becomes private.
873 *
874 * In both cases there is a temporary shared mapping to a private page,
875 * which can result in a #VE. But, there is never a private mapping to
876 * a shared page.
877 */
878 x86_platform.guest.enc_status_change_prepare = tdx_enc_status_change_prepare;
879 x86_platform.guest.enc_status_change_finish = tdx_enc_status_change_finish;
880
881 x86_platform.guest.enc_cache_flush_required = tdx_cache_flush_required;
882 x86_platform.guest.enc_tlb_flush_required = tdx_tlb_flush_required;
883
884 /*
885 * TDX intercepts the RDMSR to read the X2APIC ID in the parallel
886 * bringup low level code. That raises #VE which cannot be handled
887 * there.
888 *
889 * Intel-TDX has a secure RDMSR hypercall, but that needs to be
890 * implemented separately in the low level startup ASM code.
891 * Until that is in place, disable parallel bringup for TDX.
892 */
893 x86_cpuinit.parallel_bringup = false;
894
895 pr_info("Guest detected\n");
896}
897

source code of linux/arch/x86/coco/tdx/tdx.c