Re: [PATCH v9 29/36] x86/fred: FRED entry/exit and dispatch code

[H. Peter Anvin]

On 7/30/23 23:41, Xin Li wrote:
> +
> +static DEFINE_FRED_HANDLER(fred_sw_interrupt_user)
> +{
> +	/*
> +	 * In compat mode INT $0x80 (32bit system call) is
> +	 * performance-critical. Handle it first.
> +	 */
> +	if (IS_ENABLED(CONFIG_IA32_EMULATION) &&
> +	    likely(regs->vector == IA32_SYSCALL_VECTOR)) {
> +		regs->orig_ax = regs->ax;
> +		regs->ax = -ENOSYS;
> +		return do_int80_syscall_32(regs);
> +	}

We can presumably drop the early out here as well...

> +
> +	/*
> +	 * Some software exceptions can also be triggered as
> +	 * int instructions, for historical reasons.
> +	 */
> +	switch (regs->vector) {
> +	case X86_TRAP_BP:
> +	case X86_TRAP_OF:
> +		fred_emulate_trap(regs);
> +		break;
> +	default:
> +		regs->vector = X86_TRAP_GP;
> +		fred_emulate_fault(regs);
> +		break;
> +	}
> +}
> +