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[libvirt] [PATCH] json: Avoid passing large positive 64 bit integers to QMP.



We don't seem to be reaching any sort of sensible conclusion with qemu
about this bug, so it seems easier (albeit uglier) to fix it on the
libvirt side.

I have verified that with this patch virDomainMemoryPeek works on 64
bit guests.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://et.redhat.com/~rjones/virt-df/
>From 9def1fb4a1b59b086493cf5eb78228515933e0b7 Mon Sep 17 00:00:00 2001
From: Richard W.M. Jones <rjones redhat com>
Date: Wed, 25 May 2011 17:52:26 +0100
Subject: [PATCH] json: Avoid passing large positive 64 bit integers to QMP.

http://lists.gnu.org/archive/html/qemu-devel/2011-05/threads.html#02162

Currently, qemu silently clips any JSON integer in the range
0x8000000000000000 - 0xffffffffffffffff (all numbers in this range
will be clipped to 0x7fffffffffffffff == LLONG_MAX).

To avoid this, pass these as signed 64 bit integers in the QMP
request.
---
 src/qemu/qemu_monitor_json.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index 2d8a390..bdd0dcb 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -413,8 +413,13 @@ qemuMonitorJSONMakeCommand(const char *cmdname,
             ret = virJSONValueObjectAppendNumberLong(jargs, key, val);
         }   break;
         case 'U': {
-            unsigned long long val = va_arg(args, unsigned long long);
-            ret = virJSONValueObjectAppendNumberUlong(jargs, key, val);
+            /* qemu silently truncates numbers larger than LLONG_MAX,
+             * so passing the full range of unsigned 64 bit integers
+             * is not safe here.  Pass them as signed 64 bit integers
+             * instead.
+             */
+            long long val = va_arg(args, long long);
+            ret = virJSONValueObjectAppendNumberLong(jargs, key, val);
         }   break;
         case 'd': {
             double val = va_arg(args, double);
-- 
1.7.5.1


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