linux-kernel - Re: [Xen-devel] [PATCH] xen/balloon: don't online new memory initially

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Date:   Mon, 3 Jul 2017 18:16:55 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Jan Beulich <JBeulich@...e.com>
Cc:     xen-devel@...ts.xenproject.org, boris.ostrovsky@...cle.com,
        linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH] xen/balloon: don't online new memory
 initially

On 03/07/17 18:11, Jan Beulich wrote:
>>>> On 03.07.17 at 17:40, <jgross@...e.com> wrote:
>> --- a/drivers/xen/xen-balloon.c
>> +++ b/drivers/xen/xen-balloon.c
>> @@ -59,6 +59,8 @@ static void watch_target(struct xenbus_watch *watch,
>>  {
>>  	unsigned long long new_target;
>>  	int err;
>> +	static bool watch_fired;
>> +	static unsigned long target_diff;
> 
> It would seem to me that the types of target_diff and new_target
> should match in width, but differ in signedness.

The different width is on purpose: new_target is in kB, so it could
exceed the max page count on 32 bit systems (not that it would matter
as a guest of that size isn't possible). target_diff is a page count
so it will always fit into a long int.

Regarding signedness you are right. I probably should switch to long
for target_diff.


Juergen