// 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 <linux/export.h>
#include <linux/io.h>
#include <linux/kexec.h>
#include <asm/coco.h>
#include <asm/tdx.h>
#include <asm/vmx.h>
#include <asm/ia32.h>
#include <asm/insn.h>
#include <asm/insn-eval.h>
#include <asm/cpuid/api.h>
#include <asm/paravirt_types.h>
#include <asm/pgtable.h>
#include <asm/set_memory.h>
#include <asm/traps.h>
/* 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))
/* TDX Module call error codes */
#define TDCALL_RETURN_CODE(a) ((a) >> 32)
#define TDCALL_INVALID_OPERAND 0xc0000100
#define TDCALL_OPERAND_BUSY 0x80000200
#define TDREPORT_SUBTYPE_0 0
static atomic_long_t nr_shared;
/* Called from __tdx_hypercall() for unrecoverable failure */
noinstr void __noreturn __tdx_hypercall_failed(void)
{
instrumentation_begin();
panic("TDVMCALL failed. TDX module bug?");
}
#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_module_args args = {
.r10 = nr,
.r11 = p1,
.r12 = p2,
.r13 = p3,
.r14 = p4,
};
return __tdx_hypercall(&args);
}
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 tdcall(u64 fn, struct tdx_module_args *args)
{
if (__tdcall_ret(fn, args))
panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
}
/* Read TD-scoped metadata */
static inline u64 tdg_vm_rd(u64 field, u64 *value)
{
struct tdx_module_args args = {
.rdx = field,
};
u64 ret;
ret = __tdcall_ret(TDG_VM_RD, &args);
*value = args.r8;
return ret;
}
/* Write TD-scoped metadata */
static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)
{
struct tdx_module_args args = {
.rdx = field,
.r8 = value,
.r9 = mask,
};
return __tdcall(TDG_VM_WR, &args);
}
/**
* tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
* subtype 0) using TDG.MR.REPORT TDCALL.
* @reportdata: Address of the input buffer which contains user-defined
* REPORTDATA to be included into TDREPORT.
* @tdreport: Address of the output buffer to store TDREPORT.
*
* Refer to section titled "TDG.MR.REPORT leaf" in the TDX Module v1.0
* specification for more information on TDG.MR.REPORT TDCALL.
*
* It is used in the TDX guest driver module to get the TDREPORT0.
*
* Return 0 on success, -ENXIO for invalid operands, -EBUSY for busy operation,
* or -EIO on other TDCALL failures.
*/
int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
{
struct tdx_module_args args = {
.rcx = virt_to_phys(tdreport),
.rdx = virt_to_phys(reportdata),
.r8 = TDREPORT_SUBTYPE_0,
};
u64 ret;
ret = __tdcall(TDG_MR_REPORT, &args);
if (ret) {
if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
return -ENXIO;
else if (TDCALL_RETURN_CODE(ret) == TDCALL_OPERAND_BUSY)
return -EBUSY;
return -EIO;
}
return 0;
}
EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);
/**
* tdx_mcall_extend_rtmr() - Wrapper to extend RTMR registers using
* TDG.MR.RTMR.EXTEND TDCALL.
* @index: Index of RTMR register to be extended.
* @data: Address of the input buffer with RTMR register extend data.
*
* Refer to section titled "TDG.MR.RTMR.EXTEND leaf" in the TDX Module v1.0
* specification for more information on TDG.MR.RTMR.EXTEND TDCALL.
*
* It is used in the TDX guest driver module to allow user to extend the RTMR
* registers.
*
* Return 0 on success, -ENXIO for invalid operands, -EBUSY for busy operation,
* or -EIO on other TDCALL failures.
*/
int tdx_mcall_extend_rtmr(u8 index, u8 *data)
{
struct tdx_module_args args = {
.rcx = virt_to_phys(data),
.rdx = index,
};
u64 ret;
ret = __tdcall(TDG_MR_RTMR_EXTEND, &args);
if (ret) {
if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
return -ENXIO;
if (TDCALL_RETURN_CODE(ret) == TDCALL_OPERAND_BUSY)
return -EBUSY;
return -EIO;
}
return 0;
}
EXPORT_SYMBOL_GPL(tdx_mcall_extend_rtmr);
/**
* tdx_hcall_get_quote() - Wrapper to request TD Quote using GetQuote
* hypercall.
* @buf: Address of the directly mapped shared kernel buffer which
* contains TDREPORT. The same buffer will be used by VMM to
* store the generated TD Quote output.
* @size: size of the tdquote buffer (4KB-aligned).
*
* Refer to section titled "TDG.VP.VMCALL<GetQuote>" in the TDX GHCI
* v1.0 specification for more information on GetQuote hypercall.
* It is used in the TDX guest driver module to get the TD Quote.
*
* Return 0 on success or error code on failure.
*/
u64 tdx_hcall_get_quote(u8 *buf, size_t size)
{
/* Since buf is a shared memory, set the shared (decrypted) bits */
return _tdx_hypercall(TDVMCALL_GET_QUOTE, cc_mkdec(virt_to_phys(buf)), size, 0, 0);
}
EXPORT_SYMBOL_GPL(tdx_hcall_get_quote);
static void __noreturn tdx_panic(const char *msg)
{
struct tdx_module_args args = {
.r10 = TDX_HYPERCALL_STANDARD,
.r11 = TDVMCALL_REPORT_FATAL_ERROR,
.r12 = 0, /* Error code: 0 is Panic */
};
union {
/* Define register order according to the GHCI */
struct { u64 r14, r15, rbx, rdi, rsi, r8, r9, rdx; };
char bytes[64] __nonstring;
} message;
/* VMM assumes '\0' in byte 65, if the message took all 64 bytes */
strtomem_pad(message.bytes, msg, '\0');
args.r8 = message.r8;
args.r9 = message.r9;
args.r14 = message.r14;
args.r15 = message.r15;
args.rdi = message.rdi;
args.rsi = message.rsi;
args.rbx = message.rbx;
args.rdx = message.rdx;
/*
* This hypercall should never return and it is not safe
* to keep the guest running. Call it forever if it
* happens to return.
*/
while (1)
__tdx_hypercall(&args);
}
/*
* The kernel cannot handle #VEs when accessing normal kernel memory. Ensure
* that no #VE will be delivered for accesses to TD-private memory.
*
* TDX 1.0 does not allow the guest to disable SEPT #VE on its own. The VMM
* controls if the guest will receive such #VE with TD attribute
* TDX_TD_ATTR_SEPT_VE_DISABLE.
*
* Newer TDX modules allow the guest to control if it wants to receive SEPT
* violation #VEs.
*
* Check if the feature is available and disable SEPT #VE if possible.
*
* If the TD is allowed to disable/enable SEPT #VEs, the TDX_TD_ATTR_SEPT_VE_DISABLE
* attribute is no longer reliable. It reflects the initial state of the
* control for the TD, but it will not be updated if someone (e.g. bootloader)
* changes it before the kernel starts. Kernel must check TDCS_TD_CTLS bit to
* determine if SEPT #VEs are enabled or disabled.
*/
static void disable_sept_ve(u64 td_attr)
{
const char *msg = "TD misconfiguration: SEPT #VE has to be disabled";
bool debug = td_attr & TDX_TD_ATTR_DEBUG;
u64 config, controls;
/* Is this TD allowed to disable SEPT #VE */
tdg_vm_rd(TDCS_CONFIG_FLAGS, &config);
if (!(config & TDCS_CONFIG_FLEXIBLE_PENDING_VE)) {
/* No SEPT #VE controls for the guest: check the attribute */
if (td_attr & TDX_TD_ATTR_SEPT_VE_DISABLE)
return;
/* Relax SEPT_VE_DISABLE check for debug TD for backtraces */
if (debug)
pr_warn("%s\n", msg);
else
tdx_panic(msg);
return;
}
/* Check if SEPT #VE has been disabled before us */
tdg_vm_rd(TDCS_TD_CTLS, &controls);
if (controls & TD_CTLS_PENDING_VE_DISABLE)
return;
/* Keep #VEs enabled for splats in debugging environments */
if (debug)
return;
/* Disable SEPT #VEs */
tdg_vm_wr(TDCS_TD_CTLS, TD_CTLS_PENDING_VE_DISABLE,
TD_CTLS_PENDING_VE_DISABLE);
}
/*
* TDX 1.0 generates a #VE when accessing topology-related CPUID leafs (0xB and
* 0x1F) and the X2APIC_APICID MSR. The kernel returns all zeros on CPUID #VEs.
* In practice, this means that the kernel can only boot with a plain topology.
* Any complications will cause problems.
*
* The ENUM_TOPOLOGY feature allows the VMM to provide topology information.
* Enabling the feature eliminates topology-related #VEs: the TDX module
* virtualizes accesses to the CPUID leafs and the MSR.
*
* Enable ENUM_TOPOLOGY if it is available.
*/
static void enable_cpu_topology_enumeration(void)
{
u64 configured;
/* Has the VMM provided a valid topology configuration? */
tdg_vm_rd(TDCS_TOPOLOGY_ENUM_CONFIGURED, &configured);
if (!configured) {
pr_err("VMM did not configure X2APIC_IDs properly\n");
return;
}
tdg_vm_wr(TDCS_TD_CTLS, TD_CTLS_ENUM_TOPOLOGY, TD_CTLS_ENUM_TOPOLOGY);
}
static void reduce_unnecessary_ve(void)
{
u64 err = tdg_vm_wr(TDCS_TD_CTLS, TD_CTLS_REDUCE_VE, TD_CTLS_REDUCE_VE);
if (err == TDX_SUCCESS)
return;
/*
* Enabling REDUCE_VE includes ENUM_TOPOLOGY. Only try to
* enable ENUM_TOPOLOGY if REDUCE_VE was not successful.
*/
enable_cpu_topology_enumeration();
}
static void tdx_setup(u64 *cc_mask)
{
struct tdx_module_args args = {};
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].
*/
tdcall(TDG_VP_INFO, &args);
/*
* 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 = args.rcx & GENMASK(5, 0);
*cc_mask = BIT_ULL(gpa_width - 1);
td_attr = args.rdx;
/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);
disable_sept_ve(td_attr);
reduce_unnecessary_ve();
}
/*
* 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)
{
struct tdx_module_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);
}
static int handle_halt(struct ve_info *ve)
{
const bool irq_disabled = irqs_disabled();
/*
* HLT with IRQs enabled is unsafe, as an IRQ that is intended to be a
* wake event may be consumed before requesting HLT emulation, leaving
* the vCPU blocking indefinitely.
*/
if (WARN_ONCE(!irq_disabled, "HLT emulation with IRQs enabled"))
return -EIO;
if (__halt(irq_disabled))
return -EIO;
return ve_instr_len(ve);
}
void __cpuidle tdx_halt(void)
{
const bool irq_disabled = false;
/*
* Use WARN_ONCE() to report the failure.
*/
if (__halt(irq_disabled))
WARN_ONCE(1, "HLT instruction emulation failed\n");
}
static void __cpuidle tdx_safe_halt(void)
{
tdx_halt();
/*
* "__cpuidle" section doesn't support instrumentation, so stick
* with raw_* variant that avoids tracing hooks.
*/
raw_local_irq_enable();
}
static int read_msr(struct pt_regs *regs, struct ve_info *ve)
{
struct tdx_module_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))
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_module_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))
return -EIO;
return ve_instr_len(ve);
}
static int handle_cpuid(struct pt_regs *regs, struct ve_info *ve)
{
struct tdx_module_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))
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_module_args args = {
.r10 = TDX_HYPERCALL_STANDARD,
.r11 = hcall_func(EXIT_REASON_EPT_VIOLATION),
.r12 = size,
.r13 = EPT_READ,
.r14 = addr,
};
if (__tdx_hypercall(&args))
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];
enum insn_mmio_type mmio;
struct insn insn = {};
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 == INSN_MMIO_DECODE_FAILED))
return -EINVAL;
if (mmio != INSN_MMIO_WRITE_IMM && mmio != INSN_MMIO_MOVS) {
reg = insn_get_modrm_reg_ptr(&insn, regs);
if (!reg)
return -EINVAL;
}
if (!fault_in_kernel_space(ve->gla)) {
WARN_ONCE(1, "Access to userspace address is not supported");
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 INSN_MMIO_WRITE:
memcpy(&val, reg, size);
if (!mmio_write(size, ve->gpa, val))
return -EIO;
return insn.length;
case INSN_MMIO_WRITE_IMM:
val = insn.immediate.value;
if (!mmio_write(size, ve->gpa, val))
return -EIO;
return insn.length;
case INSN_MMIO_READ:
case INSN_MMIO_READ_ZERO_EXTEND:
case INSN_MMIO_READ_SIGN_EXTEND:
/* Reads are handled below */
break;
case INSN_MMIO_MOVS:
case INSN_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 INSN_MMIO_READ:
/* Zero-extend for 32-bit operation */
extend_size = size == 4 ? sizeof(*reg) : 0;
break;
case INSN_MMIO_READ_ZERO_EXTEND:
/* Zero extend based on operand size */
extend_size = insn.opnd_bytes;
break;
case INSN_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_module_args args = {
.r10 = TDX_HYPERCALL_STANDARD,
.r11 = hcall_func(EXIT_REASON_IO_INSTRUCTION),
.r12 = size,
.r13 = PORT_READ,
.r14 = port,
};
bool success;
u64 val;
/*
* 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);
val = success ? args.r11 : 0;
insn_assign_reg(®s->ax, val, size);
return success;
}
static bool handle_out(struct pt_regs *regs, int size, int port)
{
u64 mask = GENMASK(BITS_PER_BYTE * size - 1, 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_args args = {};
/*
* 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.
*/
tdcall(TDG_VP_VEINFO_GET, &args);
/* Transfer the output parameters */
ve->exit_reason = args.rcx;
ve->exit_qual = args.rdx;
ve->gla = args.r8;
ve->gpa = args.r9;
ve->instr_len = lower_32_bits(args.r10);
ve->instr_info = upper_32_bits(args.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;
}
}
static inline bool is_private_gpa(u64 gpa)
{
return gpa == cc_mkenc(gpa);
}
/*
* 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:
if (is_private_gpa(ve->gpa))
panic("Unexpected EPT-violation on private memory.");
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;
}
/*
* 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>".
*/
static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
{
/* Retrying the hypercall a second time should succeed; use 3 just in case */
const int max_retries_per_page = 3;
int retry_count = 0;
if (!enc) {
/* Set the shared (decrypted) bits: */
start |= cc_mkdec(0);
end |= cc_mkdec(0);
}
while (retry_count < max_retries_per_page) {
struct tdx_module_args args = {
.r10 = TDX_HYPERCALL_STANDARD,
.r11 = TDVMCALL_MAP_GPA,
.r12 = start,
.r13 = end - start };
u64 map_fail_paddr;
u64 ret = __tdx_hypercall(&args);
if (ret != TDVMCALL_STATUS_RETRY)
return !ret;
/*
* The guest must retry the operation for the pages in the
* region starting at the GPA specified in R11. R11 comes
* from the untrusted VMM. Sanity check it.
*/
map_fail_paddr = args.r11;
if (map_fail_paddr < start || map_fail_paddr >= end)
return false;
/* "Consume" a retry without forward progress */
if (map_fail_paddr == start) {
retry_count++;
continue;
}
start = map_fail_paddr;
retry_count = 0;
}
return false;
}
/*
* 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 (!tdx_map_gpa(start, end, enc))
return false;
/* shared->private conversion requires memory to be accepted before use */
if (enc)
return tdx_accept_memory(start, end);
return true;
}
static int 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 && !tdx_enc_status_changed(vaddr, numpages, enc))
return -EIO;
return 0;
}
static int 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 && !tdx_enc_status_changed(vaddr, numpages, enc))
return -EIO;
if (enc)
atomic_long_sub(numpages, &nr_shared);
else
atomic_long_add(numpages, &nr_shared);
return 0;
}
/* Stop new private<->shared conversions */
static void tdx_kexec_begin(void)
{
if (!IS_ENABLED(CONFIG_KEXEC_CORE))
return;
/*
* Crash kernel reaches here with interrupts disabled: can't wait for
* conversions to finish.
*
* If race happened, just report and proceed.
*/
if (!set_memory_enc_stop_conversion())
pr_warn("Failed to stop shared<->private conversions\n");
}
/* Walk direct mapping and convert all shared memory back to private */
static void tdx_kexec_finish(void)
{
unsigned long addr, end;
long found = 0, shared;
if (!IS_ENABLED(CONFIG_KEXEC_CORE))
return;
lockdep_assert_irqs_disabled();
addr = PAGE_OFFSET;
end = PAGE_OFFSET + get_max_mapped();
while (addr < end) {
unsigned long size;
unsigned int level;
pte_t *pte;
pte = lookup_address(addr, &level);
size = page_level_size(level);
if (pte && pte_decrypted(*pte)) {
int pages = size / PAGE_SIZE;
/*
* Touching memory with shared bit set triggers implicit
* conversion to shared.
*
* Make sure nobody touches the shared range from
* now on.
*/
set_pte(pte, __pte(0));
/*
* Memory encryption state persists across kexec.
* If tdx_enc_status_changed() fails in the first
* kernel, it leaves memory in an unknown state.
*
* If that memory remains shared, accessing it in the
* *next* kernel through a private mapping will result
* in an unrecoverable guest shutdown.
*
* The kdump kernel boot is not impacted as it uses
* a pre-reserved memory range that is always private.
* However, gathering crash information could lead to
* a crash if it accesses unconverted memory through
* a private mapping which is possible when accessing
* that memory through /proc/vmcore, for example.
*
* In all cases, print error info in order to leave
* enough bread crumbs for debugging.
*/
if (!tdx_enc_status_changed(addr, pages, true)) {
pr_err("Failed to unshare range %#lx-%#lx\n",
addr, addr + size);
}
found += pages;
}
addr += size;
}
__flush_tlb_all();
shared = atomic_long_read(&nr_shared);
if (shared != found) {
pr_err("shared page accounting is off\n");
pr_err("nr_shared = %ld, nr_found = %ld\n", shared, found);
}
}
static __init void tdx_announce(void)
{
struct tdx_module_args args = {};
u64 controls;
pr_info("Guest detected\n");
tdcall(TDG_VP_INFO, &args);
tdx_dump_attributes(args.rdx);
tdg_vm_rd(TDCS_TD_CTLS, &controls);
tdx_dump_td_ctls(controls);
}
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);
/* TSC is the only reliable clock in TDX guest */
setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
cc_vendor = CC_VENDOR_INTEL;
/* Configure the TD */
tdx_setup(&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;
x86_platform.guest.enc_kexec_begin = tdx_kexec_begin;
x86_platform.guest.enc_kexec_finish = tdx_kexec_finish;
/*
* Avoid "sti;hlt" execution in TDX guests as HLT induces a #VE that
* will enable interrupts before HLT TDCALL invocation if executed
* in STI-shadow, possibly resulting in missed wakeup events.
*
* Modify all possible HLT execution paths to use TDX specific routines
* that directly execute TDCALL and toggle the interrupt state as
* needed after TDCALL completion. This also reduces HLT related #VEs
* in addition to having a reliable halt logic execution.
*/
pv_ops.irq.safe_halt = tdx_safe_halt;
pv_ops.irq.halt = tdx_halt;
/*
* TDX intercepts the RDMSR to read the X2APIC ID in the parallel
* bringup low level code. That raises #VE which cannot be handled
* there.
*
* Intel-TDX has a secure RDMSR hypercall, but that needs to be
* implemented separately in the low level startup ASM code.
* Until that is in place, disable parallel bringup for TDX.
*/
x86_cpuinit.parallel_bringup = false;
tdx_announce();
}
