Re: [PATCH] 2.6.4-rc1 fix x86 early_printk and make it early
From: Eric W. Biederman
Date: Tue Mar 02 2004 - 03:34:29 EST
Andi Kleen <ak@xxxxxxx> writes:
> On 29 Feb 2004 22:24:12 -0700
> ebiederm@xxxxxxxxxxxx (Eric W. Biederman) wrote:
>
> > o That is problematic with PAE support, because there is a moment
> > during paging_init() when the physical identity mappings do not
> > work.
>
> Just don't printk in that moment then.
>
> > o Using raw physical addresses is in bad form, and doesn't always work.
>
> On x86-64 it's that __pa() doesn't always work very early.
>
> > o I can't possibly see how Andrew's Changelog that using __pa
> > is more friendly to the 4G/4G split is correct. Unless someone
> > was hard coding a virtual address previously.
>
> Yes, it shouldn't make any difference for 4/4.
>
> > The second hunk in early_printk.c redefines VGABASE as __va(0xb8000).
> > This is correct on both x86 and x86-64 so we don't need any more
> > special cases.
>
> Please don't do that on x86-64. On x86-64 there are two ways to reach this
> address and the previous one is available earlier. Keep the current
> address for x86-64 please.
Andi much to my great surprise after reading through the comments
that actually didn't work on x86-64. So here is my corrected patch.
It still uses __va() for everything but it fixes x86-64 so that it works,
I just had to move one page table entry...
As for 0xffff000000000000 which the old page table entry applied to
I grepped the entire kernel tree and could not find anything that
applied to x86_64. So it looks like a left over from an earlier definition
of PAGE_OFFSET.
So can we please get this applied to 2.6? Now that it is almost purely
mini bug fixes?
Eric
diff -uNrX linux-ignore-files linux-2.6.4-rc1/arch/i386/kernel/setup.c linux-2.6.4-rc1.earlyprintk/arch/i386/kernel/setup.c
--- linux-2.6.4-rc1/arch/i386/kernel/setup.c Sun Feb 29 14:09:16 2004
+++ linux-2.6.4-rc1.earlyprintk/arch/i386/kernel/setup.c Sun Feb 29 19:10:40 2004
@@ -1048,6 +1048,18 @@
{
unsigned long max_low_pfn;
+#ifdef CONFIG_EARLY_PRINTK
+ extern void setup_early_printk(char *);
+ char *str;
+
+ COMMAND_LINE[COMMAND_LINE_SIZE -1] = '\0';
+ str = strstr(COMMAND_LINE, "earlyprintk=");
+ if (str) {
+ setup_early_printk(str);
+ printk("early console enabled\n");
+ }
+#endif
+
memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
pre_setup_arch_hook();
early_cpu_init();
@@ -1117,19 +1129,6 @@
smp_alloc_memory(); /* AP processor realmode stacks in low memory*/
#endif
paging_init();
-
-#ifdef CONFIG_EARLY_PRINTK
- {
- char *s = strstr(*cmdline_p, "earlyprintk=");
- if (s) {
- extern void setup_early_printk(char *);
-
- setup_early_printk(s);
- printk("early console enabled\n");
- }
- }
-#endif
-
dmi_scan_machine();
diff -uNrX linux-ignore-files linux-2.6.4-rc1/arch/x86_64/kernel/early_printk.c linux-2.6.4-rc1.earlyprintk/arch/x86_64/kernel/early_printk.c
--- linux-2.6.4-rc1/arch/x86_64/kernel/early_printk.c Sun Feb 29 21:24:55 2004
+++ linux-2.6.4-rc1.earlyprintk/arch/x86_64/kernel/early_printk.c Sun Feb 29 21:26:02 2004
@@ -7,11 +7,7 @@
/* Simple VGA output */
-#ifdef __i386__
-#define VGABASE __pa(__PAGE_OFFSET + 0xb8000UL)
-#else
-#define VGABASE 0xffffffff800b8000UL
-#endif
+#define VGABASE __va(0xb8000UL)
#define MAX_YPOS 25
#define MAX_XPOS 80
diff -uNrX linux-ignore-files linux-2.6.4-rc1/arch/x86_64/kernel/head.S linux-2.6.4-rc1.earlyprintk/arch/x86_64/kernel/head.S
--- linux-2.6.4-rc1/arch/x86_64/kernel/head.S Sun Feb 29 14:09:23 2004
+++ linux-2.6.4-rc1.earlyprintk/arch/x86_64/kernel/head.S Tue Mar 2 01:10:52 2004
@@ -206,9 +206,10 @@
.org 0x1000
ENTRY(init_level4_pgt)
.quad 0x0000000000102007 /* -> level3_ident_pgt */
- .fill 255,8,0
+ .fill 1,8,0
+ /* 2^40/2^39 = 2 */
.quad 0x000000000010a007
- .fill 254,8,0
+ .fill 508,8,0
/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
.quad 0x0000000000103007 /* -> level3_kernel_pgt */
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/