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

From: Richard Henderson
Subject: Re: [PATCH] target/hppa: Allow, but diagnose, LDCW aligned only mod 4
Date: Fri, 17 Jan 2020 09:23:28 -1000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1

On 1/17/20 8:50 AM, Philippe Mathieu-Daudé wrote:
> On Fri, Jan 17, 2020 at 2:53 AM Richard Henderson
> <address@hidden> 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.

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


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