[PATCH][XEN] construct_dom0: Initialize variable before use

["Christoph Egger" <Christoph.Egger@amd.com>]

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Hi!

Attached patch initializes d->arch.physaddr_bitsize properly for a
64bit Dom0/64bit hypervisor.
This bug has been found when booting a NetBSD/Xen Dom0 with more
than 4GB RAM.

Without this fix, d->arch.physaddr_bitsize is 0 in 
domain_clamp_alloc_bitsize(). This causes all attempts to 
XENMEM_increase_reservation with bits > 0 to fail. More precisely,
__alloc_domheap_pages() returns NULL.
This impacts Xen heap allocation in general.
Question: How did that work on Linux Dom0?

I think, initializing physaddr_bitsize to 64 unconditionally is ok because in
construct_dom0() it is overridden with the proper value when you boot
64bit hypervisor with a 32bit Dom0. If the hypervisor is not 64bit,
physaddr_bitsize isn't used at all anyway.

Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>


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Operating System Research Center

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diff -r 6fd17d0dcbcd xen/arch/x86/domain_build.c
--- a/xen/arch/x86/domain_build.c	Tue Nov 27 12:49:16 2007 +0000
+++ b/xen/arch/x86/domain_build.c	Wed Nov 28 17:37:53 2007 +0100
@@ -353,6 +353,11 @@ int __init construct_dom0(
     if ( parms.pae == PAEKERN_extended_cr3 )
             set_bit(VMASST_TYPE_pae_extended_cr3, &d->vm_assist);
 
+    /* Unconditionally initialize this member here for 64bit Dom0s.
+     * In the below if (), this is overridden for 32bit Dom0s.
+     */ 
+    d->arch.physaddr_bitsize = 64;
+
     if ( UNSET_ADDR != parms.virt_hv_start_low && elf_32bit(&elf) )
     {
 #if CONFIG_PAGING_LEVELS < 4

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