linux-kernel - Re: [patch 3/5] i386-gdt-pda Update lguest to initialize gdt without pda

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Date:	Tue, 27 Mar 2007 13:32:18 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, Andi Kleen <ak@...e.de>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	xen-devel@...ts.xensource.com, virtualization@...ts.osdl.org
Subject: Re: [patch 3/5] i386-gdt-pda Update lguest to initialize gdt
	without pda

On Mon, 2007-03-26 at 17:21 -0700, Jeremy Fitzhardinge wrote:
> plain text document attachment (lguest-use-percpu.patch)

Thanks for the fixup Jeremy!

	Unfortunately that doesn't quite work.  But it turns out we don't need
to load the GDT at all: we can run off the Host-supplied one until we
load the gdt naturally.

So I prefer this patch:
===
Lguest now doesn't need to touch the GDT at all: it can run on the
Host-supplied boot gdt until it reloads later in the boot process.

Signed-off-by: Jeremy Fitzhardinge <jeremy@...source.com>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
Cc: Andi Kleen <ak@...e.de>
---
 arch/i386/lguest/lguest.c |   15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff -r 3349222e5f58 arch/i386/lguest/lguest.c
--- a/arch/i386/lguest/lguest.c	Tue Mar 27 12:57:46 2007 +1000
+++ b/arch/i386/lguest/lguest.c	Tue Mar 27 13:28:20 2007 +1000
@@ -34,7 +34,6 @@
 #include <asm/desc.h>
 #include <asm/setup.h>
 #include <asm/e820.h>
-#include <asm/pda.h>
 #include <asm/asm-offsets.h>
 #include <asm/mce.h>
 
@@ -448,10 +447,6 @@ static void lguest_power_off(void)
 {
 	hcall(LHCALL_CRASH, __pa("Power down"), 0, 0);
 }
-
-/* From head.S */
-extern void setup_pda(void);
-extern struct Xgt_desc_struct early_gdt_descr;
 
 static __attribute_used__ __init void lguest_init(void)
 {
@@ -513,11 +508,6 @@ static __attribute_used__ __init void lg
 	/* We use top of mem for initial pagetables. */
 	init_pg_tables_end = __pa(pg0);
 
-	/* set up PDA descriptor */
-	setup_pda();
-	load_gdt(&early_gdt_descr);
-	asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_PDA) : "memory");
-
 	reserve_top_address(lguest_data.reserve_mem);
 
 	cpu_detect(&new_cpu_data);


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