Re: [RFC PATCH] x86/insn: support decode MOVSXD instruction for MMIO

[Dave Hansen]

On 3/28/23 19:59, Wu Zongyong wrote:
> It seems MOVSXD which opcode is 0x63 is not handled, support
> to decode it in insn_decode_mmio().
...
>  	switch (insn->opcode.bytes[0]) {
> +	case 0x63: /* MOVSXD r64, m32 */
> +		*bytes = 4;
> +		type = INSN_MMIO_READ_SIGN_EXTEND;
> +		break;

The kernel does not support _arbitrary_ memory access instructions
messing with MMIO.

Before even considering this, I'd want to see a very concrete
explanation for why _this_ instruction in particular is required.  I'd
also want to make sure this doesn't set us off down a slippery slope
trying to make the MMIO decoder more expansive.