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-rw-r--r--arch/x86/coco/tdx/tdx.c834
1 files changed, 834 insertions, 0 deletions
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
new file mode 100644
index 000000000..d0565a9e7
--- /dev/null
+++ b/arch/x86/coco/tdx/tdx.c
@@ -0,0 +1,834 @@
+// 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/ia32.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;
+}
+
+static bool tdx_enc_status_change_prepare(unsigned long vaddr, int numpages,
+ bool enc)
+{
+ /*
+ * Only handle shared->private conversion here.
+ * See the comment in tdx_early_init().
+ */
+ if (enc)
+ return tdx_enc_status_changed(vaddr, numpages, enc);
+ return true;
+}
+
+static bool tdx_enc_status_change_finish(unsigned long vaddr, int numpages,
+ bool enc)
+{
+ /*
+ * Only handle private->shared conversion here.
+ * See the comment in tdx_early_init().
+ */
+ if (!enc)
+ return tdx_enc_status_changed(vaddr, numpages, enc);
+ return true;
+}
+
+void __init tdx_early_init(void)
+{
+ u64 cc_mask;
+ u32 eax, sig[3];
+
+ cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax, &sig[0], &sig[2], &sig[1]);
+
+ if (memcmp(TDX_IDENT, sig, sizeof(sig)))
+ return;
+
+ setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
+
+ cc_set_vendor(CC_VENDOR_INTEL);
+ tdx_parse_tdinfo(&cc_mask);
+ cc_set_mask(cc_mask);
+
+ /*
+ * All bits above GPA width are reserved and kernel treats shared bit
+ * as flag, not as part of physical address.
+ *
+ * Adjust physical mask to only cover valid GPA bits.
+ */
+ physical_mask &= cc_mask - 1;
+
+ /*
+ * The kernel mapping should match the TDX metadata for the page.
+ * load_unaligned_zeropad() can touch memory *adjacent* to that which is
+ * owned by the caller and can catch even _momentary_ mismatches. Bad
+ * things happen on mismatch:
+ *
+ * - Private mapping => Shared Page == Guest shutdown
+ * - Shared mapping => Private Page == Recoverable #VE
+ *
+ * guest.enc_status_change_prepare() converts the page from
+ * shared=>private before the mapping becomes private.
+ *
+ * guest.enc_status_change_finish() converts the page from
+ * private=>shared after the mapping becomes private.
+ *
+ * In both cases there is a temporary shared mapping to a private page,
+ * which can result in a #VE. But, there is never a private mapping to
+ * a shared page.
+ */
+ x86_platform.guest.enc_status_change_prepare = tdx_enc_status_change_prepare;
+ x86_platform.guest.enc_status_change_finish = tdx_enc_status_change_finish;
+
+ x86_platform.guest.enc_cache_flush_required = tdx_cache_flush_required;
+ x86_platform.guest.enc_tlb_flush_required = tdx_tlb_flush_required;
+
+ pr_info("Guest detected\n");
+}