Semi-working patch for amd64 suspend/resume

[Steve Franks]

On Tue, Dec 2, 2008 at 10:43 AM, Jung-uk Kim <jkim at freebsd.org> wrote:
> On Sunday 30 November 2008 03:10 pm, Alexander Motin wrote:
>> Hi.
>>
>> Alexander Motin wrote:
>> > Jung-uk Kim wrote:
>> >> I was working on suspend/resume support for amd64 and this is
>> >> the result.  It works with a modified QEMU (QEMU does not
>> >> support S3) but real boxes that I have don't seem to like it
>> >> (e.g., broken BIOSes). If there is someone interested in
>> >> finishing it off or giving it a try, the patch is here:
>> >>
>> >> http://people.freebsd.org/~jkim/amd64_suspend.diff
>> >
>> > I have tried it on my Acer TM6292. S1/S2 are unsupported. On S3
>> > system successfully got down, but on wakeup button, two seconds
>> > after power up, even without video initialization, it shut down,
>> > reset and then started usual boot. I have tried both original and
>> > updated BIOS, without any difference.
>> >
>> > Can I give you any other help?
>>
>> I have spent a day investigating the problem. I was inserting empty
>> infinite loop into the different points of wakeup process trying to
>> find the place where system reboots. I just haven't found any other
>> feedback channel as video is not initialized and beeper is not
>> working for some reason.
>>
>> As result, I have found, that if I am inserting:
>> qqq:
>>
>>          jmp     qqq
>> lines before line 98 of acpi_switch.S:
>>       movl    $MSR_MTRRdefType, %ecx
>>
>>          movl    WAKEUP_CTX(mtrr), %eax
>>
>>          wrmsr
>> system hangs, but if I insert it just after them - system reboots.
>>
>> With just commenting this three lines I was able to get successful
>> suspend/resume with UP amd64 kernel!!!
>
> Good catch!  I can confirm this is a correct bandaid.  We cannot
> restore this MSR without restoring entire MTRR map.  Actually, I
> should have written separate functions to save/restore all global
> MSRs.  Only per-CPU MSRs should be embedded like that.
>
>> Here is problems I still have now:
>>   - SMP kernel resume is not working, system reboots while doing
>> acpi_wakeup_cpus();
>
> My dual-core CPU seems to resume okay but quite unstable.  Can you try
> something like the following in amd64/mp_machdep.c and tell me if it
> helps?
>
> ------------
> @@ -57,6 +57,7 @@
>  #include <vm/vm_extern.h>
>
>  #include <machine/apicreg.h>
> +#include <machine/cpufunc.h>
>  #include <machine/md_var.h>
>  #include <machine/mp_watchdog.h>
>  #include <machine/pcb.h>
> @@ -1121,6 +1121,8 @@
>        int cpumask = PCPU_GET(cpumask);
>
>        if (savectx2(&stopxpcbs[cpu])) {
> +               /* Flush CPU cache. */
> +               wbinvd();
>                /* Indicate that we are suspended. */
>                atomic_set_int(&stopped_cpus, cpumask);
>        } else {
> ------------
>
>>   - text mode video does not restores on resume, while Xorg graphic
>> one does. hw.acpi.reset_video=1 does not help, it just hanging
>> resume process.
>
> It is very common problem for modern video cards.  We cannot do much
> here without help of GPU-specific routines (e.g., ATI ATOM BIOS
> parser for RadeonHD) or in-kernel realmode emulation[1] (e.g.,
> NetBSD).
>
> Thanks for the feedback!
>
> Jung-uk Kim
>
> [1] http://cvsweb.netbsd.org/bsdweb.cgi/src/common/lib/libx86emu/
> http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/arch/x86/x86/vga_post.c
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>

Do you believe these patches should work against 6.4?  I should like
to try it out on my trusty 'ol desktop.

Best,
Steve