RE: [Xen-devel] Dom heap virtual address question

[Daniel Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> But for portability, it's better to have 32bit implication
> in mind to avoid mistake. :-)

Yes, exactly what I was thinking!

> For 64bit xen, both local and global version are simply
> macros to mfn_to_virt which is a directly mapping

OK, I found this in xen/include/xen/domain_page.h
but was confused because CONFIG_DOMAIN_PAGE must
be set to zero and include/asm-x86/config.h sets
it to one.  But apparently the 64-bit build scripts
override the config.h setting and CONFIG_DOMAIN_PAGE=1
is used.

Thanks again!
Dan

> -----Original Message-----
> From: Tian, Kevin [mailto:kevin.tian@xxxxxxxxx]
> Sent: Tuesday, August 26, 2008 7:29 PM
> To: Daniel Magenheimer; Xen-Devel (E-mail)
> Subject: RE: [Xen-devel] Dom heap virtual address question
>
>
> >From: Daniel Magenheimer [mailto:dan.magenheimer@xxxxxxxxxx]
> >Sent: 2008年8月27日 9:20
> >
> >Hi Kevin --
> >
> >Thanks much for the reply.
> >
> >Further clarification on the _global versions:
> >If domainA makes a hypercall that results in the
> >
> >va = mfn_to_virt(page_to_mfn(alloc_domheap_pages()))
> >
> >(or equivalent wrapped in map/unmap_domain_page)
> >
> >and then domainB makes a hypercall but IN THE
> >HYPERVISOR I want to make use of the previously
> >saved va (or mapped mfn), is that still in the context
> >of domainA?  In other words, I must use _global?
> >
>
> Yes. The ptes used for non global version is domain
> specific, which is changed along with context switch.
> However ptes for _global version are persistent across
> domains. This is for 32bit xen.
>
> For 64bit xen, both local and global version are simply
> macros to mfn_to_virt which is a directly mapping
> style setuped at boot time. In such case, you can always
> access previously mapped va from any domain context,
> regardless of which interface is used.
>
> But for portability, it's better to have 32bit implication
> in mind to avoid mistake. :-)
>
> Thanks,
> Kevin
>

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