Re: [Xen-users] hypercall implementation

[åäé <cloud2han9@xxxxxxx>]

I talked about PV.

I know the hypercall's implementation mechanism, but hypercall's call tree.

From the book, The Definitive Guide to Xen Hypervisor, I known that the "generic builder" will automatically map the hypercall page at one page indicated by the key "HYPERCALL_PAGE" in the guest kernel elf's  section "__xen_guest " into the guest os' address space. I have searched the Xen source code. I can't find the hypercall page's source code. Where is it?

In addition,  The book mentioned above describes xen' internals well mainly in English. In order to know Xen exactly, I think I must read Xen's source code. Is there some resource(book, blog, paper, etc) descriping Xen hypervisor mainly in C language. I need a start point in Xen's source code to explore Xen hypervisor or a path through it. Do you have some suggestion ? Thangks.

Cloud Zhang.

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å2013å12æ10 19æ01åï"Ian Campbell"<Ian.Campbell@xxxxxxxxxx>åéï

>  On Tue, 2013-12-10 at 18:55 +0800, åäé wrote:
> > But what's the content (src code) of hypercall_page?
> >  How is the hypercall implemented?
>
> You need to be looking on the hypervisor side for that. It is a page of
> code which is mapped into the guest kernel and contains the necessary
> instructions (int 0x82, syscall, vmcall, etc) depending on the guest
> type etc. For a PV guest it is populated by the Xen tools asking the
> hypervisor to do so during guest build and for a PVHVM guest it is
> populated by the guest writing to a special MSR, see enlighten.c in the
> Linux kernel, specifically init_hvm_pv_info().
>
> Ian.


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