Re: [Xen-devel] [PATCH v3 2/3] x86/svm: Drop enum instruction_index and simplify svm_get_insn_len()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 31.12.18 at 12:57, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 31/12/2018 11:37, Andrew Cooper wrote:
>> +/*
>> + * Encoding for svm_get_insn_len().  We take X86EMUL_OPC() for the main
>> + * opcode, shifted left to make room for the ModRM byte.
>> + */
>> +#define INSTR_ENC(opc, modrm) (((unsigned int)(opc) << 8) | (modrm))
>> +#define MODRM(mod, reg, rm) (((mod) << 6) | ((reg) << 3) | rm)
>> +
>> +#define INSTR_PAUSE       INSTR_ENC(X86EMUL_OPC_F3(0, 0x90), 0)
>> +#define INSTR_INT3        INSTR_ENC(X86EMUL_OPC(   0, 0xcc), 0)
>> +#define INSTR_ICEBP       INSTR_ENC(X86EMUL_OPC(   0, 0xf1), 0)
>> +#define INSTR_HLT         INSTR_ENC(X86EMUL_OPC(   0, 0xf4), 0)
>> +#define INSTR_XSETBV      INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), MODRM(3, 2, 1))
>> +#define INSTR_VMRUN       INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), MODRM(3, 3, 0))
>> +#define INSTR_VMCALL      INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), MODRM(3, 3, 1))
>> +#define INSTR_VMLOAD      INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), MODRM(3, 3, 2))
>> +#define INSTR_VMSAVE      INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), MODRM(3, 3, 3))
>> +#define INSTR_STGI        INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), MODRM(3, 3, 4))
>> +#define INSTR_CLGI        INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), MODRM(3, 3, 5))
>> +#define INSTR_INVLPGA     INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), MODRM(3, 3, 7))
>> +#define INSTR_RDTSCP      INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), MODRM(3, 7, 1))
> 
> I'm still tempted to drop the MODRM() macro, and use octal notation
> 
> #define INSTR_XSETBV      INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), 0321)
> #define INSTR_VMRUN       INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), 0330)
> #define INSTR_VMCALL      INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), 0331)
> #define INSTR_VMLOAD      INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), 0332)
> #define INSTR_VMSAVE      INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), 0333)
> #define INSTR_STGI        INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), 0334)
> #define INSTR_CLGI        INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), 0335)
> #define INSTR_INVLPGA     INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), 0337)
> #define INSTR_RDTSCP      INSTR_ENC(X86EMUL_OPC(0x0f, 0x01), 0371)
> 
> Seeing as this is a far more logical way to read x86 instructions.

Fine with me, fwiw (with a comment making clear what this stands for).

Jan



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