Re: [Xen-devel] [PATCH - proposed] XI Shadow Page Table Mechanism]

[Steve Ofsthun <sofsthun@xxxxxxxxxxxxxxx>]

Robert Phillips wrote:
> Yes, that's true.  If the caller supplied a bogus PFN (one larger than 
> ram size), we'd crash.
> BTW, we are avoiding use of grant table transfers because they fragment 
> PSE pages.
> -- rsp

We also avoid grant table transfers due to incompatibilities with QEMU's one
time map of all of guest memory.  If you use grant table transfers (via
netfront/netback), the QEMU memory map quickly becomes out of date.  Any
QEMU I/O (net, or disk), will result in stale guest data being used.

> On 6/30/06, *zhu* <vanbas.han@xxxxxxxxx <mailto:vanbas.han@xxxxxxxxx>> 
> wrote:
> 
>     I'm afraid it could trigger some certain problems only when you open l2
>     PSE flag and use grant table to transfer pages between domains. I'm not
>     very sure about it. :-)
> 
>     _______________________________________________________
>     Best Regards,
>     hanzhu
> 
> 
>     Robert Phillips 写道:
>      > Hi Han,
>      > You are right again.  I have not seen this cause a problem but we'll
>      > certainly fix it.
>      > -- rsp
>      >
>      > On 6/29/06, zhu < vanbas.han@xxxxxxxxx
>     <mailto:vanbas.han@xxxxxxxxx>> wrote:
>      >>
>      >> Hi, Robert,
>      >> I found out another confusing code snippet:
>      >> in void xi_invl_mfn(struct domain *d, unsigned long mfn)
>      >>      if (ext && pfn < ext->large_page_aligned_size)
>      >>
>      >> According to the code, it should be
>      >>      if (ext && (pfn>>SPT_ENTRIES_ORDER) <
>     ext->large_page_aligned_size)
>      >>
>      >> If I made any mistake, please point it out.
>      >> _______________________________________________________
>      >> Best Regards,
>      >> hanzhu
>      >>
>      >
>      >
> 
> 
> 
> 
> -- 
> --------------------------------------------------------------------
> Robert S. Phillips                          Virtual Iron Software
> rphillips@xxxxxxxxxxxxxxx 
> <mailto:rphillips@xxxxxxxxxxxxxxx>                Tower 1, Floor 2
> 978-849-1220                                 900 Chelmsford Street
>                                                     Lowell, MA 01851
> 
> 
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-- 
Steve Ofsthun - Virtual Iron Software, Inc.

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