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Date: Mon, 22 Jan 2018 13:07:30 -0800 (PST)
From: Don Lewis <truckman@FreeBSD.org>
Subject: Re: Ryzen issues on FreeBSD ?
To: Mike Tancsa <mike@sentex.net>
cc: freebsd-stable@freebsd.org, Pete French <petefrench@ingresso.co.uk>
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On 22 Jan, Mike Tancsa wrote:
> On 1/21/2018 3:24 PM, Don Lewis wrote:
>>>
>>> I have supplied a customer with a Ryzen5 and a 350MB motherboard.
>>> But he runs Windows 10, but I haven't heard him complain about anything 
>>> like this.
>>> But I'll ask him specific.
>> 
>> Only the BSDs were affected by the shared page issue.  I think Linux
>> already had a guard page.  I don't think Windows was affected by the
>> idle C-state issue.  I suspect it is caused by software not doing the
>> right thing during C-state transitions, but the publicly available
>> documentation from AMD is pretty lacking.  The random segfault issue is
>> primarily triggered by heavy parallel software build loads and how many
>> Windows users do that?
> 
> 
> Are all the AMD accomodations that DragonFly did in FreeBSD ?
> 
> http://lists.dragonflybsd.org/pipermail/commits/2017-August/626190.html

We only lowered the top of user space by 4KB, which should be
sufficient, and we unmapped the boundary page.  The signal trampoline
was already in a separate page than the stack.