Re: [Xen-devel] [PATCH 14/38] arm: do not set max_vcpus = 8 in arch_domain_create.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2012-06-06 at 16:26 +0100, Stefano Stabellini wrote:
> On Fri, 1 Jun 2012, Ian Campbell wrote:
> > XEN_DOMCTL_max_vcpus cannot reduce max_vcpus and therefore we can't create a
> > smaller guest.
> > 
> > The limit of 8 (due to GIC limits) should be expressed elsewhere, likely in
> > MAX_VIRT_CPUS -- but making that change caused:
> 
> Are you sure? I made that change and I didn't see the error.
> I think this patch should set MAX_VIRT_CPUS to 8 as well as removing
> max_vcpus = 8.

This was the same heap corruption again as seen in "[PATCH 16/38] arm:
Add simple cpu_{sibling,core}_mask"  and having fixed that I don't see
the crash with MAX_VIRT_CPUS == 8 any more...

The patch becomes:

>From b68c4abe1dec44f3ed87a0d7ae98f4269043cce3 Mon Sep 17 00:00:00 2001
From: Ian Campbell <ian.campbell@xxxxxxxxxx>
Date: Thu, 7 Jun 2012 16:52:46 +0000
Subject: [PATCH] arm: do not set max_vcpus = 8 in arch_domain_create.

XEN_DOMCTL_max_vcpus cannot reduce max_vcpus and therefore we can't create a
smaller guest.

The limit of 8 (due to GIC limits) should be expressed in MAX_VIRT_CPUS.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 xen/arch/arm/domain.c        |    2 --
 xen/include/asm-arm/config.h |    2 +-
 2 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 1336dc4..040a2ce 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -338,8 +338,6 @@ int arch_domain_create(struct domain *d, unsigned int 
domcr_flags)
             goto fail;
     }
 
-    d->max_vcpus = 8;
-
     if ( (rc = domain_vgic_init(d)) != 0 )
         goto fail;
 
diff --git a/xen/include/asm-arm/config.h b/xen/include/asm-arm/config.h
index 91e87e1..7d02cc7 100644
--- a/xen/include/asm-arm/config.h
+++ b/xen/include/asm-arm/config.h
@@ -27,7 +27,7 @@
 #define NR_CPUS 128
 #endif
 
-#define MAX_VIRT_CPUS 128 /* XXX */
+#define MAX_VIRT_CPUS 8
 #define MAX_HVM_VCPUS MAX_VIRT_CPUS
 
 #define asmlinkage /* Nothing needed */
-- 
1.7.9.1




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