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Re: [PATCH] domain: use unsigned loop induction variable in complete_domain_destroy()
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 4 Mar 2026 16:48:07 +0100
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>
- Delivery-date: Wed, 04 Mar 2026 15:48:34 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 04.03.2026 16:38, Roger Pau Monné wrote:
> On Thu, Feb 26, 2026 at 10:01:45AM +0100, Jan Beulich wrote:
>> --- a/xen/common/domain.c
>> +++ b/xen/common/domain.c
>> @@ -1475,7 +1475,7 @@ static void cf_check complete_domain_des
>> {
>> struct domain *d = container_of(head, struct domain, rcu);
>> struct vcpu *v;
>> - int i;
>> + unsigned int i;
>>
>> /*
>> * Flush all state for the vCPU previously having run on the current
>> CPU.
>> @@ -1485,7 +1485,7 @@ static void cf_check complete_domain_des
>> */
>> sync_local_execstate();
>>
>> - for ( i = d->max_vcpus - 1; i >= 0; i-- )
>> + for ( i = d->max_vcpus; i-- > 0; )
>
> Is there any reason we need to do those loops backwards?
>
> I would rather do:
>
> for ( i = 0; i < d->max_vcpus; i++ )
>
> ?
I think it's better to keep like this. The latter of the loops would better
clear d->vcpu[i] (to not leave a dangling pointer), and there may be code
which assumes that for ordinary domains d->vcpu[] is populated contiguously.
Hardly any code should touch the vCPU-s of a domain destructed this far, but
still better safe than sorry, I guess.
In no case would I like to mix both changes.
Jan
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