[Xen-ia64-devel] Re: [Xen-devel] [PATCH] Fix DMA emualtion for ia64.

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Zhang, Xiantao writes ("[Xen-devel] [PATCH] Fix DMA emualtion for ia64."):
>     In Xen3.4-RC3, we found a regression for creating hvm domains
> and this issue is discussed in the thread
> http://www.nabble.com/A-strange-issue-when-VTI-guest-vcpus-number-is-near-pcpus-td23400397.html.
>  This
> patch is a key fix for Xen-3.4. Without this patch, all hvm guests
> maybe crash during booting stage. Could you help to apply it for
> next release?  Thanks!

Thanks for the report and the patch, which I'm applying.  But I did
have some questions.

These changes are largely to code which we've inherited unchanged from
upstream qemu.  Are they specific to Xen ?  I suspect not.  I don't
really know about the icache coherency rules in ia64 but it seems to
me that if this patch is appropriate for qemu-dm on ia64, it's
probably also appropriate for kvm-userpace on ia64 (if indeed there is
such a thing) and perhaps also for ordinary translating cpu-emulating
qemu.

In which case perhaps it would be good for us to discuss with qemu
upstream how to address this question.  I don't think the #ifdef
__ia64__ can be right outside the Xen context; for one thing, we
should use a symbol related to specifically to either the host or the
target architecture (which may be different in qemu of course).  I
assume that the problem exists related to ia64 hosts, rather than ia64
guests ?

Ian.

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