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Subject: Re: [PATCH] powerpc/rtas: Restrict RTAS requests from userspace
To: Daniel Axtens <dja@axtens.net>, Michael Ellerman <mpe@ellerman.id.au>,
 linuxppc-dev@lists.ozlabs.org
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From: Andrew Donnellan <ajd@linux.ibm.com>
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Date: Wed, 12 Aug 2020 13:13:32 +1000
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 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

On 11/8/20 11:41 pm, Daniel Axtens wrote:
>>>> +static bool block_rtas_call(int token, int nargs,
>>>> +			    struct rtas_args *args)
>>>> +{
>>>> +	int i;
>>>> +	const char *reason;
>>>> +	char *token_name = rtas_token_name(token);
>>>
>>> This code isn't particularly performance critical, but I think it would
>>> be cleaner to do the token lookup once at init time, and store the token
>>> in the filter array?
>>>
>>> Then this code would only be doing token comparisons.
>>
>> Yeah that would be cleaner, can get rid of rtas_token_name().
> 
> I'm not sure I quite understand what you're suggesting.
> 
> You still need to do a string->token lookup at least once as the tokens
> differ between PowerVM and qemu. Are you saying that you can fold the
> token name lookup into the init function?

Yeah, mpe is suggesting adding a member to the struct to cache the token 
value, and then just looping through all of them to populate that field 
at init time.

-- 
Andrew Donnellan              OzLabs, ADL Canberra
ajd@linux.ibm.com             IBM Australia Limited