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

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Subject: Re: [Xen-ia64-devel] Community effort neededtocatch upwithxen-unstable
From: John Byrne <john.l.byrne@xxxxxx>
Date: Fri, 02 Sep 2005 11:17:09 -0700
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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


With all the various patches, things work fine and I get a login prompt.

I knew the x86 model was different, what I didn't know was what you did with this patch was legal. It looks to me as if you have the operating system accessing a page the VM really shouldn't let it have. I was trying to figure out how to reserve the page in the EFI memory map: add it to the end of the hypercall page or something. Maybe its fortunate I had to go home so you could come up with the more straightforward fix.

Spoke a little too soon, again. Looks like dom0 just crashed hard:

(XEN) +01+01Heartbeat... iip=f0000000040092d0,psr.i=0,pend=1
(XEN) +01ia64_fault: General Exception: IA-64 Reserved Register/Field fault (data access): reflecting

I've no clue what the problem might be, things were idle. Still, things are better.



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