From: "H. Peter Anvin" <hpa@zytor.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: matt@console-pimps.org, matt.fleming@intel.com, mingo@kernel.org,
x86@kernel.org, mjg@redhat.com, linux-efi@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] x86, mm: Include the entire kernel memory map in trampoline_pgd
Date: Fri, 05 Oct 2012 09:28:00 -0700 [thread overview]
Message-ID: <506F0A90.7020106@zytor.com> (raw)
In-Reply-To: <506E9CDC020000780009FD13@nat28.tlf.novell.com>
On 10/04/2012 11:39 PM, Jan Beulich wrote:
>>
>> We should have the check, but at least for Linux support we require
>> P <= V-2.
>
> Not really imo - P <= V - 1 should be sufficient here, as all that is
> necessary is that the result represents a 1:1 mapping. Specifically,
> there's no constraint to the virtual space limitation of the direct
> mapping of RAM.
>
The P <= V-2 limitation doesn't come from this, it comes from the fact
that we need to have the regular kernel 1:1 map and still have space for
the kernel, vmalloc, ioremap and so on in the kernel part of the address
space; in theory it *could* be some fraction between 1 and 2, but since
hardware doesn't do fractional bits very well the above is what we have
been telling the hardware folks. :)
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2012-10-05 16:28 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-03 12:59 [PATCH 0/3] x86/efi: Identity mapping pagetable Matt Fleming
2012-10-03 12:59 ` [PATCH 1/3] x86, mm: Include the entire kernel memory map in trampoline_pgd Matt Fleming
2012-10-03 13:31 ` Jan Beulich
2012-10-03 14:03 ` Matt Fleming
2012-10-04 6:32 ` Jan Beulich
2012-10-04 9:18 ` Matt Fleming
2012-10-04 10:01 ` Jan Beulich
2012-10-10 10:45 ` Matt Fleming
[not found] ` <1349865920.15966.327.camel-ZqTwcBeJ+wsBof6jY8KHXm7IUlhRatedral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2012-10-15 7:22 ` Jan Beulich
2012-10-15 7:22 ` Jan Beulich
2012-10-04 21:08 ` H. Peter Anvin
2012-10-05 6:39 ` Jan Beulich
2012-10-05 6:48 ` Matt Fleming
2012-10-05 8:19 ` Jan Beulich
2012-10-05 16:28 ` H. Peter Anvin [this message]
2012-10-07 8:16 ` Jan Beulich
2012-10-07 10:26 ` H. Peter Anvin
2012-10-08 6:43 ` Jan Beulich
2012-10-03 12:59 ` [PATCH 2/3] x86, efi: 1:1 pagetable mapping for virtual EFI calls Matt Fleming
2012-10-03 12:59 ` [PATCH 3/3] x86/kernel: remove tboot 1:1 page table creation code Matt Fleming
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