Re: [Xen-devel] Memory Sharing

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 08:17 +0100 on 24 May (1306225059), Lakshitha Harshan wrote:
> Hi,
> 
> I'm using Xen 4.1.1-rc1-pre on linux-xen-2.6.32.39-g057b171. I'm trying to 
> use memory sharing functions. In my code i call,
> 
> uint64_t shandle, chandle;
>  xc_memshr_nominate_gfn(xc_handle,dom1,4200,&shandle); //dom1 & dom2 are 
> Debian Squeeze domUs
>  xc_memshr_nominate_gfn(xc_handle,dom2,4200,&shandle); // gfn 4200 is a 
> memory page in kernel code segment
> xc_memshr_share(xc_handle, shandle, chandle);
> 
> I use xl dmesg and following is the output.
> 
> (XEN) sh error: sh_remove_all_mappings(): can't find all mappings of mfn 
> 42f01: c=8000000000000002 t=8400000000000001
> (XEN) sh error: sh_remove_all_mappings(): can't find all mappings of mfn 
> 42f01: c=8000000000000002 t=8400000000000001
> (XEN) sh error: sh_remove_all_mappings(): can't find all mappings of mfn 
> 9c502: c=8000000000000002 t=8400000000000001
> (XEN) sh error: sh_remove_all_mappings(): can't find all mappings of mfn 
> 42f02: c=8000000000000002 t=8400000000000001
> (XEN) sh error: sh_remove_all_mappings(): can't find all mappings of mfn 
> 42f02: c=8000000000000002 t=8400000000000001
> (XEN) printk: 2695593 messages suppressed.
> (XEN) mm.c:907:d1 Error getting mfn 9c625 (pfn fffffffffffffffe) from L1 
> entry 000000009c625021 for l1e_owner=1, pg_owner=1
> (XEN) printk: 2768333 messages suppressed.
> 
> After this operations the cpu usage of domUs goes to 97-100% and I can't 
> shutdown them. So when i issue "xl destroy""the system reboots.
> 
> What could be the reason? Any help greatly 

Memory sharing is only supportes with HAP (that is, you must have a CPU
with NPT or EPT support, and not have "hap=0" in your VM configuration
file). 

The reboot is unfortunate; there should really be a more graceful
failure mode if memory sharing is turned on with shadow pagetables.

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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