Re: S3 resume issues

[Malcolm Crossley <malcolm.crossley@citrix.com>]

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On 02/01/13 16:46, Ben Guthro wrote:
> On Wed, Jan 2, 2013 at 10:31 AM, Ben Guthro <ben@guthro.net 
> <mailto:ben@guthro.net>> wrote:
>
>         The actual wakeup vector is wakeup_start in
>         xen/arch/x86/boot/wakeup.S
>
>
>     I'll take a look at this, thanks for the pointer.
>
>
> I've tried putting a "ud2" instruction at the start of wakeup_start - 
> and the machine doesn't seem to crash.
> I also tried a divide by zero in the same place, just for good measure.
>
> It would appear that this wakeup_start is not getting executed on resume.
> Presumably, the BIOS is causing the disk, and CDROM LEDs to flash, 
> while enumerating the bus.
>
> A difference between Xen 4.0.y and 4.2.y seems to be the removal of 
> the boot trampoline fixed address, that much of this is calculated as 
> an offset of.
> Could an error in this path cause such a behavior?

It seems the trampoline is allocated at a different location in Xen 4.2 
(EBDA - 64k instead of 0x7c000). I have attached a quick patch to move 
the location back to 0x7c000 to see if that helps your system. I have 
compile and boot tested the patch but not had time to do a S3 test on 
it. Can you try it on your system?

Can you also run the following command as root in dom0:

hexdump -s 0x400 -n 32 /dev/mem
>
> /btg

Malcolm

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# HG changeset patch
# Parent a98b2e22ecbb57fee6b061dee3e3fb264fbf6f4e
Test patch!: Force x86 boot trampoline to be allocated at 0x7c000 instead of EBDA - 64k

diff -r a98b2e22ecbb xen/arch/x86/boot/head.S
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -77,8 +77,8 @@ gdt_boot_descr:
         cmp     $0x2BADB002,%eax
         jne     not_multiboot
 
-        /* Set up trampoline segment 64k below EBDA */
-        movzwl  0x40e,%eax          /* EBDA segment */
+        /* Hard code trampoline to 0x7c000 */
+        mov     $0x8c00,%eax        /* hardcoded 0x8c00 */
         cmp     $0xa000,%eax        /* sanity check (high) */
         jae     0f
         cmp     $0x4000,%eax        /* sanity check (low) */

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