Re: [Xen-devel] [PATCH] xen/hvc: If we use xen_raw_printk let it also work on HVM guests.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

Ian Campbell <ian.campbell@xxxxxxxxxx> wrote:
>On Tue, 2013-08-20 at 15:35 -0400, Konrad Rzeszutek Wilk wrote:
>>  void xen_raw_console_write(const char *str)
>>  {
>> -    dom0_write_console(0, str, strlen(str));
>> +    ssize_t len = strlen(str);
>> +    int rc = 0;
>> +
>> +    if (xen_domain()) {
>> +            rc = dom0_write_console(0, str, len);
>> +            if (rc != len && xen_hvm_domain()) /* -ENOSYS */
>
>If you want to catch ENOSYS then I suggest doing so explicitly, rather
>that relying on len != -ENOSYS.
>
>> +                    goto outb_print;
>
>How about reversing this into
>       if (rc == len) return;
>       if (rc != -ENOSYS) panic(...) /* yes, this won't get far... *.
>
>Then fall through to the following block as a plain if not an else if.
>Maybe with a xen_hvm_domain && added.
>
>That avoids the yucky goto I think.
>
>> +    } else if (xen_cpuid_base()) {
>> +            int i;
>> +outb_print:
>> +            for (i = 0; i < len; i++)
>> +                    outb(str[i], 0xe9);
>> +    }
>>  }
>>  
>>  void xen_raw_printk(const char *fmt, ...)

B/c the function  dom0_write_console never returns negative values.  Instead it 
converts it to a zero return value. Perhaps it can return negative values -  
will have to look. 

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