From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@muc.de>,
lkml - Kernel Mailing List <linux-kernel@vger.kernel.org>,
virtualization <virtualization@lists.osdl.org>
Subject: Re: [PATCH 5/7] Use %gs for per-cpu sections in kernel
Date: Sun, 24 Sep 2006 22:25:57 -0700 [thread overview]
Message-ID: <45176865.7020300@goop.org> (raw)
In-Reply-To: <1159152678.26986.38.camel@localhost.localdomain>
Rusty Russell wrote:
> That can't happen, since 0xc100000 is not in the kernel address space.
> 0xc1000000 is though, perhaps that's what you meant?
>
Yes, it is. Though it doesn't actually make any material difference to
my argument.
>> So, in this case the %gs base will be loaded with 0xc100000-0xc0431100 =
>> 0x4bccef00
>>
>
>
> A negative offset, exactly, which can't happen, as I said.
0x4bccef00 is positive. The correct number is 0xc1000000-0xc0431100 =
0xbcef00
The %gs:per_cpu__foo addressing mode still calculates
0xbcef00+0xc0433800, which is still a subtraction. My essential point
is that *all* kernel addresses (=kernel symbols) are negative, so using
them as an offset from a segment base (any segment base) is a
subtraction, which requires a 4G limit.
J
next prev parent reply other threads:[~2006-09-25 5:25 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-09-22 11:51 [PATCH 0/7] Using %gs for per-cpu areas on x86 Rusty Russell
2006-09-22 11:53 ` [PATCH 1/7] Use per-cpu GDT tables from early in boot Rusty Russell
2006-09-22 11:55 ` [PATCH 2/7] Rusty Russell
2006-09-22 11:56 ` [PATCH 3/7] Update sys_vm86 to cope with changed pt_regs and %gs usage Rusty Russell
2006-09-22 11:58 ` [PATCH 4/7] Fix places where using %gs changes the usermode ABI Rusty Russell
2006-09-22 11:59 ` [PATCH 5/7] Use %gs for per-cpu sections in kernel Rusty Russell
2006-09-22 12:00 ` [PATCH 6/7] (Optional) implement smp_processor_id() as a per-cpu var Rusty Russell
2006-09-22 12:01 ` [PATCH 7/7] (Optional) implement current " Rusty Russell
2006-09-25 5:29 ` Rusty Russell
2006-09-25 5:27 ` [PATCH 6/7] (Optional) implement smp_processor_id() " Rusty Russell
2006-09-22 12:32 ` [PATCH 5/7] Use %gs for per-cpu sections in kernel Andi Kleen
2006-09-22 22:43 ` Jeremy Fitzhardinge
2006-09-22 23:52 ` Andi Kleen
2006-09-23 4:51 ` Rusty Russell
2006-09-23 8:17 ` Andi Kleen
2006-09-23 8:55 ` Rusty Russell
2006-09-22 22:39 ` Jeremy Fitzhardinge
2006-09-23 4:31 ` Rusty Russell
2006-09-25 1:03 ` Jeremy Fitzhardinge
2006-09-25 1:16 ` Rusty Russell
2006-09-25 1:36 ` Jeremy Fitzhardinge
2006-09-25 2:51 ` Rusty Russell
2006-09-25 5:25 ` Jeremy Fitzhardinge [this message]
2006-09-25 6:03 ` Rusty Russell
2006-09-25 6:25 ` Jeremy Fitzhardinge
2006-09-25 23:33 ` Rusty Russell
2006-09-23 8:13 ` Andi Kleen
2006-09-25 1:07 ` Jeremy Fitzhardinge
2006-09-25 1:20 ` Rusty Russell
2006-09-25 5:26 ` Rusty Russell
2006-09-22 22:24 ` [PATCH 2/7] Jeremy Fitzhardinge
2006-09-23 4:36 ` Rusty Russell
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