From: "H. Peter Anvin" <hpa@zytor.com>
To: Andreas Herrmann <herrmann.der.user@googlemail.com>
Cc: Jacob Shin <jacob.shin@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
Yinghai Lu <yinghai@kernel.org>
Subject: Re: [PATCH 1/1] x86, e820: Remove direct mapping of reserved space for HT hole around 1TB
Date: Thu, 13 Oct 2011 08:52:47 -0700 [thread overview]
Message-ID: <4E97094F.6050900@zytor.com> (raw)
In-Reply-To: <20111013095734.GA16748@alberich.amd.com>
On 10/13/2011 02:57 AM, Andreas Herrmann wrote:
>
> So what is the point in including address space below TOM2 not backed
> with memory in kernel's direct mapping? For similar reserved space
> before 4GB we don't do this.
>
> Instead of barfing, some more constructive feedback would be
> appreciated.
>
Ok, that's a BUG, plain and simple, and a very serious one (for exactly
the reason you just described.) We should NEVER have cachable mappings
for a RESERVED region because it can have arbitrary side effects, so the
fact that that happens at all is the real problem and it MUST be addressed.
So I'm not arguing that it is not a problem for you (it is a real and
serious problem), but I would like to see it addressed correctly, which
is to exclude these memory regions from direct mapping just as we do for
< 4 GB. That way the fix applies to any RESERVED region.
-hpa
next prev parent reply other threads:[~2011-10-13 15:53 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-11 22:09 [PATCH 1/1] x86, e820: Remove direct mapping of reserved space for HT hole around 1TB Jacob Shin
2011-10-11 23:44 ` H. Peter Anvin
2011-10-13 9:57 ` Andreas Herrmann
2011-10-13 15:52 ` H. Peter Anvin [this message]
2011-10-13 11:04 ` Andreas Herrmann
2011-10-14 5:45 ` Yinghai Lu
2012-10-16 16:47 ` Shuah Khan
[not found] <6ec48b96-afab-4c8b-ab74-2c640c2a161b@blur>
[not found] ` <8630fe28-0c1c-4f3a-90e1-df2d1b6615a6@blur>
2012-10-16 17:48 ` Shuah Khan
2012-10-16 18:26 ` Jacob Shin
2012-10-16 19:02 ` H. Peter Anvin
2012-10-17 15:30 ` Shuah Khan
2012-10-17 18:25 ` H. Peter Anvin
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