From: Zwane Mwaikambo <zwane@arm.linux.org.uk>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH][2.6] Dont use cpu_has_pse for WP test branch
Date: Tue, 4 Nov 2003 11:36:28 -0500 (EST) [thread overview]
Message-ID: <Pine.LNX.4.53.0311041130040.20595@montezuma.fsmlabs.com> (raw)
In-Reply-To: <Pine.LNX.4.44.0311040809470.20373-100000@home.osdl.org>
On Tue, 4 Nov 2003, Linus Torvalds wrote:
> Why?
>
> The reason we test the PSE bit is not that we think it's a good indicator
> of "new enough". It's because if the PSE bit is set, we will use 4MB
> pages, and the code below that actually _tests_ whether WP works or not
> won't work.
Agreed, i also retracted the patch due to the reasons behind cpu_has_pse
not working was because of CONFIG_DEBUG_PAGEALLOC.
> In fact, these days we could remove the test entirely: the only reason it
> exists is because traditionally we didn't have the "fixmap" helpers, so we
> used the page in lowest kernel memory for testing (which did not exist if
> we had PSE, since with PSE the kernel wouldn't use individual pages to map
> itself).
Wasn't the test unconditional in 2.4? How about the following then?
Index: linux-2.6.0-test9-mm1/arch/i386/mm/init.c
===================================================================
RCS file: /build/cvsroot/linux-2.6.0-test9-mm1/arch/i386/mm/init.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 init.c
--- linux-2.6.0-test9-mm1/arch/i386/mm/init.c 30 Oct 2003 11:22:42 -0000 1.1.1.1
+++ linux-2.6.0-test9-mm1/arch/i386/mm/init.c 4 Nov 2003 16:34:45 -0000
@@ -390,12 +390,6 @@ void __init paging_init(void)
void __init test_wp_bit(void)
{
- if (cpu_has_pse) {
- /* Ok, all PSE-capable CPUs are definitely handling the WP bit right. */
- boot_cpu_data.wp_works_ok = 1;
- return;
- }
-
printk("Checking if this processor honours the WP bit even in supervisor mode... ");
/* Any page-aligned address will do, the test is non-destructive */
prev parent reply other threads:[~2003-11-04 16:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-04 7:07 [PATCH][2.6] Dont use cpu_has_pse for WP test branch Zwane Mwaikambo
2003-11-04 9:33 ` Zwane Mwaikambo
2003-11-04 16:13 ` Linus Torvalds
2003-11-04 16:36 ` Zwane Mwaikambo [this message]
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