From: "Kirill A. Shutemov" <kirill.shute...@linux.intel.com>
Handle #VE due to MMIO operations. MMIO triggers #VE with EPT_VIOLATION exit reason. For now we only handle subset of instruction that kernel uses for MMIO oerations. User-space access triggers SIGBUS. Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com> Reviewed-by: Andi Kleen <a...@linux.intel.com> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppusw...@linux.intel.com> --- arch/x86/kernel/tdx.c | 120 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+) diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c index 3846d2807a7a..eff58329751e 100644 --- a/arch/x86/kernel/tdx.c +++ b/arch/x86/kernel/tdx.c @@ -6,6 +6,8 @@ #include <linux/cpu.h> #include <asm/tdx.h> #include <asm/vmx.h> +#include <asm/insn.h> +#include <linux/sched/signal.h> /* force_sig_fault() */ #ifdef CONFIG_KVM_GUEST #include "tdx-kvm.c" @@ -270,6 +272,121 @@ static void tdx_handle_io(struct pt_regs *regs, u32 exit_qual) } } +static unsigned long tdx_mmio(int size, bool write, unsigned long addr, + unsigned long val) +{ + register long r10 asm("r10") = TDVMCALL_STANDARD; + register long r11 asm("r11") = EXIT_REASON_EPT_VIOLATION; + register long r12 asm("r12") = size; + register long r13 asm("r13") = write; + register long r14 asm("r14") = addr; + register long r15 asm("r15") = val; + register long rcx asm("rcx"); + long ret; + + /* Allow to pass R10, R11, R12, R13, R14 and R15 down to the VMM */ + rcx = BIT(10) | BIT(11) | BIT(12) | BIT(13) | BIT(14) | BIT(15); + + asm volatile(TDCALL + : "=a"(ret), "=r"(r10), "=r"(r11), "=r"(r12), "=r"(r13), + "=r"(r14), "=r"(r15) + : "a"(TDVMCALL), "r"(rcx), "r"(r10), "r"(r11), "r"(r12), + "r"(r13), "r"(r14), "r"(r15) + : ); + + WARN_ON(ret || r10); + + return r11; +} + +static inline void *get_reg_ptr(struct pt_regs *regs, struct insn *insn) +{ + static const int regoff[] = { + offsetof(struct pt_regs, ax), + offsetof(struct pt_regs, cx), + offsetof(struct pt_regs, dx), + offsetof(struct pt_regs, bx), + offsetof(struct pt_regs, sp), + offsetof(struct pt_regs, bp), + offsetof(struct pt_regs, si), + offsetof(struct pt_regs, di), + offsetof(struct pt_regs, r8), + offsetof(struct pt_regs, r9), + offsetof(struct pt_regs, r10), + offsetof(struct pt_regs, r11), + offsetof(struct pt_regs, r12), + offsetof(struct pt_regs, r13), + offsetof(struct pt_regs, r14), + offsetof(struct pt_regs, r15), + }; + int regno; + + regno = X86_MODRM_REG(insn->modrm.value); + if (X86_REX_R(insn->rex_prefix.value)) + regno += 8; + + return (void *)regs + regoff[regno]; +} + +static int tdx_handle_mmio(struct pt_regs *regs, struct ve_info *ve) +{ + int size; + bool write; + unsigned long *reg; + struct insn insn; + unsigned long val = 0; + + /* + * User mode would mean the kernel exposed a device directly + * to ring3, which shouldn't happen except for things like + * DPDK. + */ + if (user_mode(regs)) { + pr_err("Unexpected user-mode MMIO access.\n"); + force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *) ve->gla); + return 0; + } + + kernel_insn_init(&insn, (void *) regs->ip, MAX_INSN_SIZE); + insn_get_length(&insn); + insn_get_opcode(&insn); + + write = ve->exit_qual & 0x2; + + size = insn.opnd_bytes; + switch (insn.opcode.bytes[0]) { + /* MOV r/m8 r8 */ + case 0x88: + /* MOV r8 r/m8 */ + case 0x8A: + /* MOV r/m8 imm8 */ + case 0xC6: + size = 1; + break; + } + + if (inat_has_immediate(insn.attr)) { + BUG_ON(!write); + val = insn.immediate.value; + tdx_mmio(size, write, ve->gpa, val); + return insn.length; + } + + BUG_ON(!inat_has_modrm(insn.attr)); + + reg = get_reg_ptr(regs, &insn); + + if (write) { + memcpy(&val, reg, size); + tdx_mmio(size, write, ve->gpa, val); + } else { + val = tdx_mmio(size, write, ve->gpa, val); + memset(reg, 0, size); + memcpy(reg, &val, size); + } + return insn.length; +} + void __init tdx_early_init(void) { if (!cpuid_has_tdx_guest()) @@ -331,6 +448,9 @@ int tdx_handle_virtualization_exception(struct pt_regs *regs, case EXIT_REASON_IO_INSTRUCTION: tdx_handle_io(regs, ve->exit_qual); break; + case EXIT_REASON_EPT_VIOLATION: + ve->instr_len = tdx_handle_mmio(regs, ve); + break; default: pr_warn("Unexpected #VE: %d\n", ve->exit_reason); return -EFAULT; -- 2.25.1