Re: [Xen-devel] [PATCH 2/2] xen/dom0: Add a dom0-iommu=none option

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 21/12/2018 12:13, Jan Beulich wrote:
>>>> On 21.12.18 at 00:40, <andrew.cooper3@xxxxxxxxxx> wrote:
>> @@ -271,6 +272,26 @@ int parse_boolean(const char *name, const char *s, 
>> const char *e)
>>      return -1;
>>  }
>>  
>> +int cmdline_strcmp(const char *frag, const char *name)
> __init ?

I think there are some runtime parameters in need of some fixing as well.

>
>> +{
>> +    while ( 1 )
>> +    {
>> +        int res = (*frag - *name);
>> +
>> +        if ( res || *name == '\0' )
>> +        {
>> +            /* NUL in 'name' matching punctuation in 'frag' implies 
>> success. */
>> +            if ( *name == '\0' && ispunct(*frag) )
>> +                res = 0;
> Isn't ispunct() true for dashes and perhaps also underscores?
> I don't think it can be this generic, the more that ...
>
>> --- a/xen/include/xen/lib.h
>> +++ b/xen/include/xen/lib.h
>> @@ -79,6 +79,13 @@ int parse_bool(const char *s, const char *e);
>>   */
>>  int parse_boolean(const char *name, const char *s, const char *e);
>>  
>> +/**
>> + * Very similar to strcmp(), but will declare a match if the NUL in 'name'
>> + * lines up with punctuationin 'frag'.  Designed for picking exact string
>> + * matches out of a comma-separated command line fragment.
>> + */
>> +int cmdline_strcmp(const char *frag, const char *name);
> ... you talk of commas only here.

I actually borrowed this function from my CPUID cmdline patch.  In 99%
of cases, we only need to match = and , but we have some other
parameters such as psr= which use : for delimiters, hence the use of
ispunct().

As an alternative, I could revert back to explicitly checking the
expected punctuation.  It is not as if this is a fastpath.

~Andrew

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