Re: [Xen-devel] libxl: cannot start guest

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2012-05-22 at 16:32 +0100, Christoph Egger wrote:
> On 05/22/12 17:21, Ian Campbell wrote:
> 
> > On Tue, 2012-05-22 at 16:16 +0100, Christoph Egger wrote:
> >> On 05/22/12 16:20, Ian Campbell wrote:
> >>> All the >= checks on *xcg_handle seem wrong to me. Really they should be
> >>> checking != NULL, since otherwise they don't actually discriminate the
> >>> two cases! Does making that change help?
> >>
> >> Yes, that helps! I can start guests again.
> > 
> > Excellent, I assume you are going to submit the patch (i.e. I don't need
> > to..)
> 
> Yes, patch attached.

I fixed up the commit message as follows. I'll apply if IanJ agrees or
acks it.

8<-----------------------------

>From 6b43ca97f5f8c4fa9bf24101253af21bc66ddf96 Mon Sep 17 00:00:00 2001
From: Christoph Egger <Christoph.Egger@xxxxxxx>
Date: Tue, 22 May 2012 17:32:21 +0200
Subject: [PATCH] xenstore: fix crash on platforms with no gntdev driver 
implementation.

Fix pointer checks introduced in changeset 24757:aae516b78fce.

Signed-off-by: Christoph Egger <Christoph.Egger@xxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 tools/xenstore/xenstored_domain.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/xenstore/xenstored_domain.c 
b/tools/xenstore/xenstored_domain.c
index f8c822f..bf83d58 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -167,7 +167,7 @@ static int readchn(struct connection *conn, void *data, 
unsigned int len)
 
 static void *map_interface(domid_t domid, unsigned long mfn)
 {
-       if (*xcg_handle >= 0) {
+       if (*xcg_handle != NULL) {
                /* this is the preferred method */
                return xc_gnttab_map_grant_ref(*xcg_handle, domid,
                        GNTTAB_RESERVED_XENSTORE, PROT_READ|PROT_WRITE);
@@ -179,7 +179,7 @@ static void *map_interface(domid_t domid, unsigned long mfn)
 
 static void unmap_interface(void *interface)
 {
-       if (*xcg_handle >= 0)
+       if (*xcg_handle != NULL)
                xc_gnttab_munmap(*xcg_handle, interface, 1);
        else
                munmap(interface, getpagesize());
-- 
1.7.2.5




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