RE: [Xen-ia64-devel] Community effort neededtocatch upwithxen-unstable

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

>From: John Byrne [mailto:john.l.byrne@xxxxxx]
>
>I think the problem is that your latest patch plops the store page in
>the middle of kernel memory and nothing prevents the kernel from using
>it. In x86, this is handled by allocating the xenstore and console
pages
>immediately after the kernel and then setting the pt_base parameter so
>that they are never used. I'm not sure about this, but I don't see
>anything keeping from using it.
>
>I'm off for the night.
>
>John

So you're talking problem from when booting domU? You're right about the
x86 behavior, but that's different on current ia64 model. Dan prefers to
adopt a transparent virtualization mechanism, so minimal changes are
required to touch common linux code. If we also place those system pages
after the kernel image, you have to modify efi syb-system to ignore
these pages.

Currently I just put the last page allocated to xenU as the store page,
not in the middle. But yes, there's still one problem in dom_fw_init,
where all allocated pages are exposed to domain. Instead we should
reserve the last page and let store page out of domain's scope. Check
whether following changes solves your issue:

diff -r 8799d14bef77 xen/arch/ia64/dom_fw.c
--- a/xen/arch/ia64/dom_fw.c    Thu Aug 25 22:53:20 2005
+++ b/xen/arch/ia64/dom_fw.c    Fri Sep  2 10:38:11 2005
@@ -512,6 +512,11 @@
                return 0;
        }
 */
+
+       /* Last page is for xenstore, and not exported to domain */
+       if (d != dom0)
+               maxmem = (d->max_pages - 1) * PAGE_SIZE;
+
        memset(fw_mem, 0, fw_mem_size);

 #ifdef XEN

Thanks,
Kevin

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