KVM: clean up directives to compile out irqfds

[thirdparty/kernel/stable.git] / arch / x86 / coco / tdx / tdx.c

// 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 <asm/coco.h>
#include <asm/tdx.h>
#include <asm/vmx.h>
#include <asm/insn.h>
#include <asm/insn-eval.h>
#include <asm/pgtable.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))

#define ATTR_DEBUG              BIT(0)
#define ATTR_SEPT_VE_DISABLE    BIT(28)

/* TDX Module call error codes */
#define TDCALL_RETURN_CODE(a)   ((a) >> 32)
#define TDCALL_INVALID_OPERAND  0xc0000100

#define TDREPORT_SUBTYPE_0      0

/* 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);
}

/**
 * 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, -EINVAL for invalid operands, 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 -EINVAL;
                return -EIO;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);

/**
 * 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 str[64];
        } message;

        /* VMM assumes '\0' in byte 65, if the message took all 64 bytes */
        strtomem_pad(message.str, 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);
}

static void tdx_parse_tdinfo(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);

        /*
         * 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 = args.rdx;
        if (!(td_attr & ATTR_SEPT_VE_DISABLE)) {
                const char *msg = "TD misconfiguration: SEPT_VE_DISABLE attribute must be set.";

                /* Relax SEPT_VE_DISABLE check for debug TD. */
                if (td_attr & ATTR_DEBUG)
                        pr_warn("%s\n", msg);
                else
                        tdx_panic(msg);
        }
}

/*
 * 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();

        if (__halt(irq_disabled))
                return -EIO;

        return ve_instr_len(ve);
}

void __cpuidle tdx_safe_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 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,
                .r15 = *val,
        };

        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;
        }

        /*
         * 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,
        };
        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);

        /* 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_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 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)
{
        struct tdx_module_args args = {
                .rdx = TDCS_NOTIFY_ENABLES,
                .r9 = -1ULL,
        };
        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;
        tdx_parse_tdinfo(&cc_mask);
        cc_set_mask(cc_mask);

        /* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
        tdcall(TDG_VM_WR, &args);

        /*
         * 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;

        /*
         * 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 seperately in the low level startup ASM code.
         * Until that is in place, disable parallel bringup for TDX.
         */
        x86_cpuinit.parallel_bringup = false;

        pr_info("Guest detected\n");
}