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Re: [Xen-devel] Hypercall-page initialization

On 7 Feb 2006, at 16:20, Jacob Gorm Hansen wrote:

I my unprivileged domain builder, I have run into the problem of how
to setup the hypercall-page. I suppose I can decode the kernel binary
header to figure out where to put the page, and then memcpy it from
loader to linux and things will work.

But wouldn't it be better if the hypercall used to populate the page
was available to the domU, so that its startup-code could call on Xen
to populate the page? I find the current approach of hardcoding the
page location in the kernel header pretty ugly.

We can make the hypercall for filling the page one that can be executed by unpriv domains (i.e., make it not a dom0_op).

Or if you want to fill it in from within the domU, how about if we did something like reserve some space of MSRs for Xen use (e.g., hex Bxxxxxxx). Then we could say that, if the guest writes an MFN to a particular one of those MSRs, it gets filled with hypercall-page goodness. :-)

 -- Keir

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