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From: Alexander van Heukelum <heukelum@mailshack.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>, Ingo Molnar <mingo@elte.hu>
Cc: Alexander van Heukelum <heukelum@fastmail.fm>,
	Mark McLoughlin <markmc@redhat.com>,
	Ian Campbell <ijc@hellion.org.uk>,
	"H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@suse.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] reserve end-of-conventional-memory to 1MB, 32-bit, use paravirt_enabled
Date: Tue, 4 Mar 2008 19:57:42 +0100	[thread overview]
Message-ID: <20080304185742.GA12193@mailshack.com> (raw)
In-Reply-To: <47CD82C5.8060605@goop.org>

Jeremy Fitzhardinge pointed out that looking at the boot_params
struct to determine if the system is running in a paravirtual
environment is not reliable for the Xen case, currently. He also
points out that there already exists a function to determine if
the system is running in a paravirtual environment. So let's use
that instead. This gets rid of the preprocessor test too.

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>

---

On Tue, Mar 04, 2008 at 09:11:33AM -0800, Jeremy Fitzhardinge wrote:
> Alexander van Heukelum wrote:
> >On Tue, 04 Mar 2008 07:18:48 -0800, "Jeremy Fitzhardinge"
> ><jeremy@goop.org> said:
> >>Yes, is_paravirt() already exists for this purpose.
> >
> >Hi,
> >
> >If it exists, it is well-hidden. A grep for is_paravirt on the testing
> >tree turns up nothing. Did you get the name right?
> >  
> 
> Nope.  paravirt_enabled().

Duh, I should have been able to find that :-/. Thanks for the pointer.

> Just because something is paravirtualized and uses a non-PC 
> hardware_subarch doesn't mean this stuff isn't present.  Even the 
> paravirt_enabled() test isn't accurate, because the environment may 
> still choose to emulate these things (or in the Xen dom0 case, it may 
> directly expose the real hardware).

paravirt_enabled() returns 0 if CONFIG_PARAVIRT is not set, or if a
paravirt-enabled kernel is run on bare hardware: dom0. If that is right,
then it is exactly what is needed.

Greetings,
	Alexander

diff --git a/arch/x86/kernel/setup_32.c b/arch/x86/kernel/setup_32.c
index 20e537b..f595d7b 100644
--- a/arch/x86/kernel/setup_32.c
+++ b/arch/x86/kernel/setup_32.c
@@ -64,6 +64,7 @@
 #include <setup_arch.h>
 #include <bios_ebda.h>
 #include <asm/cacheflush.h>
+#include <asm/processor.h>
 
 /* This value is set up by the early boot code to point to the value
    immediately after the boot time page tables.  It contains a *physical*
@@ -408,12 +409,8 @@ static void __init reserve_ebda_region(void)
 	/* that area is absent. We'll just have to assume */
 	/* that the paravirt case can handle memory setup */
 	/* correctly, without our help. */
-#ifdef CONFIG_PARAVIRT
-	if ((boot_params.hdr.version >= 0x207) &&
-			(boot_params.hdr.hardware_subarch != 0)) {
+	if (paravirt_enabled())
 		return;
-	}
-#endif
 
 	/* end of low (conventional) memory */
 	lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES);


  reply	other threads:[~2008-03-04 18:59 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-24 17:46 [PATCH] Fix alignment of early reservation for EBDA Alexander van Heukelum
2008-02-24 19:27 ` Andi Kleen
2008-02-24 19:41 ` Ingo Molnar
2008-02-24 20:53   ` Alexander van Heukelum
2008-02-25  2:18 ` H. Peter Anvin
2008-02-25 16:54   ` Alexander van Heukelum
2008-02-25 17:01     ` Ingo Molnar
2008-02-25 18:07       ` [PATCH] reserve_early end-of-conventional-memory to 1MB Alexander van Heukelum
2008-02-25 18:13         ` H. Peter Anvin
2008-02-25 19:46           ` Alexander van Heukelum
2008-02-25 21:17             ` H. Peter Anvin
2008-02-26  9:30             ` Ingo Molnar
2008-02-27 14:26               ` Andi Kleen
2008-02-27 14:38               ` [PATCH] reserve_early end-of-conventional-memory to 1MB II - some numbers to put it into perspective Andi Kleen
2008-02-27 16:44                 ` H. Peter Anvin
2008-02-27 20:01                 ` Alexander van Heukelum
2008-02-28 13:13         ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit Alexander van Heukelum
2008-02-28 13:28           ` [RFC] use realmode code to reserve end-of-conventional-memory to 1MB Alexander van Heukelum
2008-02-28 21:12             ` Ian Campbell
2008-02-28 21:14               ` H. Peter Anvin
2008-02-28 23:16                 ` Ian Campbell
2008-02-29 20:00                   ` Ingo Molnar
2008-03-04 11:41                   ` Mark McLoughlin
2008-03-04 14:33                     ` Ingo Molnar
2008-03-04 15:12                       ` Ian Campbell
2008-03-04 15:13                       ` Jeremy Fitzhardinge
2008-03-04 15:25                         ` Ingo Molnar
2008-03-04 16:02                           ` Jeremy Fitzhardinge
2008-03-04 16:15                             ` Ingo Molnar
2008-03-04 16:15                       ` Mark McLoughlin
2008-03-04 16:23                         ` Ingo Molnar
2008-03-04 17:44                   ` Jeremy Fitzhardinge
2008-03-05 15:59                   ` Eduardo Habkost
2008-03-05 16:08                     ` H. Peter Anvin
2008-03-05 16:53                       ` Eduardo Habkost
2008-03-05 17:28                         ` H. Peter Anvin
2008-03-05 17:28                           ` Jeremy Fitzhardinge
2008-03-05 17:38                             ` H. Peter Anvin
2008-03-05 16:38                     ` Jeremy Fitzhardinge
2008-03-05 17:27                       ` H. Peter Anvin
2008-02-28 21:09           ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit Ian Campbell
2008-02-29 11:49             ` Alexander van Heukelum
2008-02-29 17:14               ` Mark McLoughlin
2008-02-29 18:38                 ` Alexander van Heukelum
2008-02-29 18:44                   ` H. Peter Anvin
2008-02-29 18:56                     ` Alexander van Heukelum
2008-02-29 22:06                   ` Mark McLoughlin
2008-02-29 22:26                     ` Alexander van Heukelum
2008-03-01 16:09                     ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit v2 Alexander van Heukelum
2008-03-01 16:12                       ` [PATCH] reserve end-of-conventional-memory to 1MB on 64-bit add-on Alexander van Heukelum
2008-03-04 11:44                       ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit v2 Mark McLoughlin
2008-03-04 13:31                         ` Alexander van Heukelum
2008-03-04 14:49                         ` Ingo Molnar
2008-03-04 15:16                           ` Mark McLoughlin
2008-03-04 15:24                             ` Ingo Molnar
2008-03-04 15:18                         ` Jeremy Fitzhardinge
2008-03-04 16:51                           ` Alexander van Heukelum
2008-03-04 17:05                             ` H. Peter Anvin
2008-03-04 17:11                             ` Jeremy Fitzhardinge
2008-03-04 18:57                               ` Alexander van Heukelum [this message]
2008-03-04 19:12                                 ` [PATCH] reserve end-of-conventional-memory to 1MB, 64-bit, use paravirt_enabled Alexander van Heukelum
2008-02-27 14:25     ` [PATCH] Fix alignment of early reservation for EBDA Andi Kleen

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