linux-kernel - Re: [PATCH 30/30] x32: Add x32 VDSO support

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Message-ID: <4F43F701.80205@zytor.com>
Date:	Tue, 21 Feb 2012 11:56:49 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andrew Lutomirski <luto@....edu>
CC:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	mingo@...nel.org, tglx@...utronix.de,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	hjl.tools@...il.com
Subject: Re: [PATCH 30/30] x32: Add x32 VDSO support

On 02/21/2012 11:51 AM, Andrew Lutomirski wrote:
>>
>> No, that wouldn't help.  The situation is actually quite similar to the
>> current situation where we have an unshared fourth level, but since the
>> fourth entries are 512G per entry, we would have to push unsharing of
>> the kernel address space at least one more level (1G), possibly two
>> (2M).  Painful.
>>
>> The main advantage of a separate cr3 would be that we wouldn't need the
>> unshared top level for the kernel side.
> 
> Also, as is, if the top level wants to be per-cpu *and* per-task,
> that's a big explosion of page tables that all need to stay in sync.
> 

Fair enough.

	-hpa

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