Re: [XenPPC] xm save/restore tests

[Jimi Xenidis <jimix@xxxxxxxxxxxxxx>]

Thanks Yi,
On Nov 9, 2006, at 5:22 PM, geyi wrote:

> Jimi,
>
> We made several tests on the save/restore with different guest  
> domain configuration.  Here is the problems we meet in the tests:
> 1. Cannot get the pfn list on large domain (domain memory >= 1GB).  
> The xc_get_pfn_list will fail for large domain, because the  
> xemcomm_create only allocate 1 page for the address mapping table  
> between two domains. That restricts the pfn_list size transferred  
> in one hcall to less than 2MB. And in current implementation, we  
> can't transfer the pfn_list by two hcalls.  So to support the large  
> domain save/restore, either the getmemlist hcall should be modified  
> to support partially pfn_list transfer or the xencomm allocate more  
> pages for the address mapping in an hcall. What's you advice?
> This is the kernel message we got from domain 0:
>         xencomm_init: could only translate 2093048 of 2129920 bytes
>         xencomm_init failure: -28
This is a known problem, when the dust settles on out next Xen  
upstream merge (in progress), I hope to have this interface fixed.
> 2.  We tried to restore a domain with disk root file system. I used  
> Hao's disk image file for the testing. The restored domain will  
> trap into Data Access Exception(300). We found that's because the  
> global pointer "shared" was not NULL before gnttab_resume is called  
> in kernel resuming. The domain can be restored successfully when we  
> clear the value of shared  to NULL in gnttab_suspend.
Hmm, x86 does not check for NULL, it is inserted in the existing  
address space.
I think setting it to NULL is a good idea.
Good catch.
Can you resend the diff below as a "signed-off" patch to the list?
> --
> Yi Ge <kudva@xxxxxxxxxxxxxx>
> diff -r b03ebb287fa9 drivers/xen/core/gnttab.c
> --- a/drivers/xen/core/gnttab.c Fri Nov 03 17:58:22 2006 -0500
> +++ b/drivers/xen/core/gnttab.c Thu Nov 09 15:40:35 2006 -0500
> @@ -426,7 +426,9 @@ int gnttab_suspend(void)
>  int gnttab_suspend(void)
>  {
>  #ifdef CONFIG_PPC_XEN
> -       return arch_gnttab_suspend(shared);
> +       int ret =  arch_gnttab_suspend(shared);
> +       shared = NULL;
> +       return ret;
>  #else
>  #if !defined(__ia64__)
>         apply_to_page_range(&init_mm, (unsigned long)shared,
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