From: "H. Peter Anvin" <hpa@zytor.com>
To: ykzhao <yakui.zhao@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, Jack Steiner <steiner@sgi.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"lenb@kernel.org" <lenb@kernel.org>,
"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC] - Mapping ACPI tables as CACHED
Date: Tue, 17 Aug 2010 08:51:41 -0700 [thread overview]
Message-ID: <4C6AB00D.8020901@zytor.com> (raw)
In-Reply-To: <1279895165.13929.61.camel@localhost.localdomain>
On 07/23/2010 07:26 AM, ykzhao wrote:
>
> Yes. We can't map the corresponding ACPI region as cached under the
> following case:
> >No E820_ACPI region is reported by BIOS. In such case the ACPI
> table resides in the NVS region
>
Why could we not map the NVS region as cached? That doesn't seem to
make sense. In practice, at least, on all BIOSes I've seen the NVS
region is just another hunk of RAM.
Sample from a real system:
BIOS-e820: 000000007d6b0000 - 000000007d6cc000 (ACPI data)
BIOS-e820: 000000007d6cc000 - 000000007d700000 (ACPI NVS)
Both are clearly RAM.
If you're not talking about the e820 NVS region, that might be a
different thing, but for the ROM region in the legacy area, the fixed
MTRRs are often set up to allow caching, and we should be able to map
them cacheable, e.g. on this system:
00000-9FFFF write-back
A0000-BFFFF uncachable
C0000-CFFFF write-protect
D0000-DFFFF uncachable
E0000-FFFFF write-protect
Clearly cacheable.
-hpa
next prev parent reply other threads:[~2010-08-17 15:52 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-22 15:22 [RFC] - Mapping ACPI tables as CACHED Jack Steiner
2010-07-22 15:52 ` Len Brown
2010-07-23 16:38 ` Jack Steiner
2010-07-23 1:46 ` ykzhao
2010-07-23 7:23 ` Ingo Molnar
2010-07-23 14:26 ` ykzhao
2010-08-17 14:45 ` Jack Steiner
2010-08-17 15:51 ` H. Peter Anvin [this message]
2010-08-17 14:42 ` Jack Steiner
2010-08-17 14:39 ` Jack Steiner
2010-07-24 0:14 ` Henrique de Moraes Holschuh
2010-07-24 0:45 ` Matthew Garrett
2010-07-24 12:26 ` Henrique de Moraes Holschuh
2010-08-17 14:49 ` Jack Steiner
2010-08-17 16:02 ` Linus Torvalds
2010-08-24 21:39 ` H. Peter Anvin
2010-08-26 17:17 ` [RFC - V2] " Jack Steiner
2010-08-26 18:08 ` H. Peter Anvin
2010-12-08 21:22 ` Jack Steiner
2010-12-09 1:27 ` H. Peter Anvin
2010-12-09 3:50 ` Jack Steiner
2010-12-09 6:12 ` Len Brown
2010-08-17 15:59 ` [RFC] " Jack Steiner
2010-08-26 17:47 ` Len Brown
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