Messages in this thread | | | Subject | Re: [PATCHv3 3/4] x86/insn-eval: Introduce insn_decode_mmio() | From | Tom Lendacky <> | Date | Mon, 29 Nov 2021 15:29:15 -0600 |
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On 11/3/21 10:45 AM, Kirill A. Shutemov wrote: > From: "Kirill A. Shutemov" <kirill@shutemov.name> > > In preparation for sharing MMIO instruction decode between SEV-ES and > TDX, factor out the common decode into a new insn_decode_mmio() helper. > > For regular virtual machine, MMIO is handled by the VMM and KVM > emulates instructions that caused MMIO. But, this model doesn't work > for a secure VMs (like SEV or TDX) as VMM doesn't have access to the > guest memory and register state. So, for TDX or SEV VMM needs > assistance in handling MMIO. It induces exception in the guest. Guest > has to decode the instruction and handle it on its own. > > The code is based on the current SEV MMIO implementation. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Reviewed-by: Andi Kleen <ak@linux.intel.com> > Reviewed-by: Tony Luck <tony.luck@intel.com> > --- > arch/x86/include/asm/insn-eval.h | 12 +++++ > arch/x86/lib/insn-eval.c | 84 ++++++++++++++++++++++++++++++++ > 2 files changed, 96 insertions(+) > > diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h > index 5c6869565fb3..010d31726d06 100644 > --- a/arch/x86/include/asm/insn-eval.h > +++ b/arch/x86/include/asm/insn-eval.h > @@ -29,4 +29,16 @@ int insn_fetch_from_user_inatomic(struct pt_regs *regs, > bool insn_decode_from_regs(struct insn *insn, struct pt_regs *regs, > unsigned char buf[MAX_INSN_SIZE], int buf_size); > > +enum mmio_type { > + MMIO_DECODE_FAILED, > + MMIO_WRITE, > + MMIO_WRITE_IMM, > + MMIO_READ, > + MMIO_READ_ZERO_EXTEND, > + MMIO_READ_SIGN_EXTEND, > + MMIO_MOVS, > +}; > + > +enum mmio_type insn_decode_mmio(struct insn *insn, int *bytes); > + > #endif /* _ASM_X86_INSN_EVAL_H */ > diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c > index 385232a67281..ffd040c1c97b 100644 > --- a/arch/x86/lib/insn-eval.c > +++ b/arch/x86/lib/insn-eval.c > @@ -1560,3 +1560,87 @@ bool insn_decode_from_regs(struct insn *insn, struct pt_regs *regs, > > return true; > } > + > +/** > + * insn_decode_mmio() - Decode a MMIO instruction > + * @insn: Structure to store decoded instruction > + * @bytes: Returns size of memory operand > + * > + * Decodes instruction that used for Memory-mapped I/O. > + * > + * Returns: > + * > + * Type of the instruction. Size of the memory operand is stored in > + * @bytes. If decode failed, MMIO_DECODE_FAILED returned. > + */ > +enum mmio_type insn_decode_mmio(struct insn *insn, int *bytes) > +{ > + int type = MMIO_DECODE_FAILED;
Wouldn't "enum mmio_type" vs "int" be better here ?
Thanks, Tom
> + > + *bytes = 0; > + > + if (insn_get_opcode(insn)) > + return MMIO_DECODE_FAILED; > + > + switch (insn->opcode.bytes[0]) { > + case 0x88: /* MOV m8,r8 */ > + *bytes = 1; > + fallthrough; > + case 0x89: /* MOV m16/m32/m64, r16/m32/m64 */ > + if (!*bytes) > + *bytes = insn->opnd_bytes; > + type = MMIO_WRITE; > + break; > + > + case 0xc6: /* MOV m8, imm8 */ > + *bytes = 1; > + fallthrough; > + case 0xc7: /* MOV m16/m32/m64, imm16/imm32/imm64 */ > + if (!*bytes) > + *bytes = insn->opnd_bytes; > + type = MMIO_WRITE_IMM; > + break; > + > + case 0x8a: /* MOV r8, m8 */ > + *bytes = 1; > + fallthrough; > + case 0x8b: /* MOV r16/r32/r64, m16/m32/m64 */ > + if (!*bytes) > + *bytes = insn->opnd_bytes; > + type = MMIO_READ; > + break; > + > + case 0xa4: /* MOVS m8, m8 */ > + *bytes = 1; > + fallthrough; > + case 0xa5: /* MOVS m16/m32/m64, m16/m32/m64 */ > + if (!*bytes) > + *bytes = insn->opnd_bytes; > + type = MMIO_MOVS; > + break; > + > + case 0x0f: /* Two-byte instruction */ > + switch (insn->opcode.bytes[1]) { > + case 0xb6: /* MOVZX r16/r32/r64, m8 */ > + *bytes = 1; > + fallthrough; > + case 0xb7: /* MOVZX r32/r64, m16 */ > + if (!*bytes) > + *bytes = 2; > + type = MMIO_READ_ZERO_EXTEND; > + break; > + > + case 0xbe: /* MOVSX r16/r32/r64, m8 */ > + *bytes = 1; > + fallthrough; > + case 0xbf: /* MOVSX r32/r64, m16 */ > + if (!*bytes) > + *bytes = 2; > + type = MMIO_READ_SIGN_EXTEND; > + break; > + } > + break; > + } > + > + return type; > +} >
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