linux-kernel - Re: [PATCH 1/5] x86-32: Split cache flush handler from simd handler

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Date:	Fri, 19 Mar 2010 15:33:25 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Brian Gerst <brgerst@...il.com>
CC:	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] x86-32: Split cache flush handler from simd handler

On 03/18/2010 11:20 AM, Brian Gerst wrote:
> Make the cache flush handler a seperate function, and use
> an alternative to call the appropriate handler.
>  
> +#ifdef CONFIG_X86_32
> +dotraplinkage void
> +do_cache_flush_error(struct pt_regs *regs, long error_code)
> +{
> +	conditional_sti(regs);
> +
> +	/*
> +	 * Handle strange cache flush from user space exception.
> +	 * This is undocumented behaviour.
> +	 */
> +	if (regs->flags & X86_VM_MASK) {
> +		handle_vm86_fault((struct kernel_vm86_regs *)regs, error_code);
> +		return;
> +	}
> +	current->thread.trap_no = 19;
> +	current->thread.error_code = error_code;
> +	die_if_kernel("cache flush denied", regs, error_code);
> +	force_sig(SIGSEGV, current);
> +}
> +#endif

Does anyone have *any idea* what processor this applies to?  I've
tracked the code back all the way to the original inclusion in the
kernel, and there isn't even the slightest hint.

The comment, of course, is a great example on how *not* to write
comments... it should have mentioned the CPU in question.

	-hpa
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