Re: amd64-agp vs. swsusp

[Michal Schmidt]

Pavel Machek wrote:
> Long time ago there were i386 problems because we assumed that kernel
> is mapped in one big mapping and agp broke that assumption. Copying
> pages backwards "fixed" it (and then we done proper fix). It should
> not be, but it seems similar to this problem....

Do you mean this patch of yours?:
http://www.ussg.iu.edu/hypermail/linux/kernel/0404.3/0640.html

I'm trying to do something similar for x86_64. See the attached patch.
Unfortunately, it doesn't help. The behaviour seems unchanged (resume 
still works iff amd64-agp wasn't loaded before suspend).

Michal
diff -Nurp -X dontdiff.new linux-mm/arch/x86_64/kernel/suspend_asm.S linux-mm.mich/arch/x86_64/kernel/suspend_asm.S
--- linux-mm/arch/x86_64/kernel/suspend_asm.S	2005-06-30 01:00:53.000000000 +0200
+++ linux-mm.mich/arch/x86_64/kernel/suspend_asm.S	2005-07-21 11:53:17.000000000 +0200
@@ -41,7 +41,7 @@ ENTRY(swsusp_arch_suspend)
 
 ENTRY(swsusp_arch_resume)
 	/* set up cr3 */	
-	leaq	init_level4_pgt(%rip),%rax
+	leaq	swsusp_level4_pgt(%rip),%rax
 	subq	$__START_KERNEL_map,%rax
 	movq	%rax,%cr3
 
diff -Nurp -X dontdiff.new linux-mm/arch/x86_64/mm/init.c linux-mm.mich/arch/x86_64/mm/init.c
--- linux-mm/arch/x86_64/mm/init.c	2005-07-18 19:48:12.000000000 +0200
+++ linux-mm.mich/arch/x86_64/mm/init.c	2005-07-21 11:21:36.000000000 +0200
@@ -310,10 +310,32 @@ void __init init_memory_mapping(unsigned
 
 extern struct x8664_pda cpu_pda[NR_CPUS];
 
+#ifdef CONFIG_SOFTWARE_SUSPEND
+/*
+ * Swap suspend & friends need this for resume because things like the intel-agp
+ * driver might have split up a kernel 4MB mapping.
+ */
+char __nosavedata swsusp_level4_pgt[PAGE_SIZE]
+	__attribute__ ((aligned (PAGE_SIZE)));
+
+static inline void save_pg_dir(void)
+{
+	memcpy(swsusp_level4_pgt, init_level4_pgt, PAGE_SIZE);
+}
+#else
+static inline void save_pg_dir(void)
+{
+}
+#endif
+
 /* Assumes all CPUs still execute in init_mm */
 void zap_low_mappings(void)
 {
-	pgd_t *pgd = pgd_offset_k(0UL);
+	pgd_t *pgd;
+
+	save_pg_dir();
+
+	pgd = pgd_offset_k(0UL);
 	pgd_clear(pgd);
 	flush_tlb_all();
 }