Re: [PATCH] target/hppa: Allow, but diagnose, LDCW aligned only mod 4

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 1/17/20 8:23 PM, Richard Henderson wrote:
> On 1/17/20 8:50 AM, Philippe Mathieu-Daudé wrote:
>> On Fri, Jan 17, 2020 at 2:53 AM Richard Henderson
>> <richard.henderson@linaro.org> wrote:
>>>
>>> The PA-RISC 1.1 specification says that LDCW must be aligned mod 16
>>> or the operation is undefined.  However, real hardware only generates
>>> an unaligned access trap for unaligned mod 4.
>>
>> This Linux kernel commit seems relevant:
>>
>> https://github.com/torvalds/linux/commit/14e256c107304#diff-e85862c7227599cb24e36494f75948d5R159-R164
>>
>>    /* From: "Jim Hull" <jim.hull of hp.com>
>>    I've attached a summary of the change, but basically, for PA 2.0, as
>>    long as the ",CO" (coherent operation) completer is specified, then the
>>    16-byte alignment requirement for ldcw and ldcd is relaxed, and instead
>>    they only require "natural" alignment (4-byte for ldcw, 8-byte for
>>    ldcd). */
> 
> It isn't completely relevant.  We don't implement hppa 2.0.

Oh... It was late and I misread it as:

   if (PA2)
     ...
   else
     ... "instead of PA 2.0 ... the 16-byte alignment ... is
     relaxed, and insted only require "natural" alignment ..."

   endif

> 
> I added a TODO comment for HPPA64, as I said in reply to Dave Anglin elsewhere
> in this thread.