Re: port-xen/37761: recent xen3/i386 domu kernel doesn't boot

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Tue, Jan 15, 2008 at 11:45:00AM +0000, yamt%mwd.biglobe.ne.jp@localhost 
wrote:
> >Description:
> 
>       a recent kernel doesn't boot.
> 
>       % sudo xm create -c kernel=./20080113 /etc/xen/nbsd
>       Using config file "/etc/xen/nbsd".
>       Started domain nbsd
>       xenconsole: Could not read tty from store: No such file or directory
>       %
>       
>       an old kernel with the same kernel config works fine.
> 
>       i've put some files at ftp://ftp.netbsd.org/pub/NetBSD/misc/yamt/6/.
>               20080112.gz     working kernel (gzipped)
>               20080113.gz     not working kernel (gzipped)
>               nbsd            /etc/xen/nbsd (see above)
>               XENU            a kernel config
>               XENU.base       a file included by XENU
> 

The attached patch should fix it (it does for me). The issue was that your
kernel is smaller than XEN3_DOMU, and needs one less L2 slot. Then
pmap_bootstrap()/initi386() falls in this empty slot when it wants to map a
few things (e.g. idt_vaddr) before calling pmap_growkernel().

I can't commit it right now, I'll do in a few hours.

-- 
Manuel Bouyer, LIP6, Universite Paris VI.           
Manuel.Bouyer%lip6.fr@localhost
     NetBSD: 26 ans d'experience feront toujours la difference
--

Index: xen/x86/x86_xpmap.c
===================================================================
RCS file: /cvsroot/src/sys/arch/xen/x86/x86_xpmap.c,v
retrieving revision 1.4
diff -u -r1.4 x86_xpmap.c
--- xen/x86/x86_xpmap.c 11 Jan 2008 20:00:52 -0000      1.4
+++ xen/x86/x86_xpmap.c 15 Jan 2008 16:09:39 -0000
@@ -161,8 +162,8 @@
        for (va = base; va < end; va += PAGE_SIZE) {
                KASSERT(va >= VM_MIN_KERNEL_ADDRESS);
                ptp = kvtopte(va);
-               XENPRINTF(("xen_set_ldt %p %d %p %p\n", (void *)base,
-                             entries, ptp, maptp));
+               XENPRINTF(("xen_set_ldt %p %d %p\n", (void *)base,
+                             entries, ptp));
                pmap_pte_clearbits(ptp, PG_RW);
        }
        s = splvm();
@@ -553,6 +554,13 @@
                count++;
        }
 #ifndef __x86_64__
+       /*
+        * one more L2 page: we'll alocate several pages after kva_start
+        * in pmap_bootstrap() before pmap_growkernel(), which have not been
+        * counted here. It's not a big issue to allocate one more L2 as
+        * pmap_growkernel() will be called anyway.
+        */
+       count++;
        nkptp[1] = count;
 #endif