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Re: Fwd: New Defects reported by Coverity Scan for XenProject
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Wed, 28 Feb 2024 13:27:51 +0000
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- Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
- Delivery-date: Wed, 28 Feb 2024 13:27:56 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 28/02/2024 1:26 pm, Roger Pau Monné wrote:
> On Wed, Feb 28, 2024 at 02:04:23PM +0100, Jan Beulich wrote:
>> On 28.02.2024 13:19, Andrew Cooper wrote:
>>> Take 2, hopefully with Stewart's correct email address this time.
>>>
>>> ~Andrew
>>>
>>> On 28/02/2024 12:17 pm, Andrew Cooper wrote:
>>>> Not sure how well this is going to be formatted, but there's one new and
>>>> potentially interesting issue found by Coverity.
>> To be honest I didn't consider this interesting at all, but instead a false
>> positive due to limited insight that the tool has. But maybe I was wrong
>> and you see something I didn't see? vpci_process_pending() is vCPU-local
>> (run from the guest resume path), and hence there simply are no two threads
>> who want to look at the field. Storing NULL into it is merely a kind of
>> progress indicator, relevant to the given vCPU only.
> Indeed, there's no (intended) way for vpci_process_pending() to be
> executed concurrently against the same vcpu parameter, and hence there
> should be no concurrency hazards. Setting it to NULL is a mere
> indication there's no further work to be done, and the vCPU can resume
> guest context execution.
>
> defer_map() (the function that queues the work to be done) can only be
> reached as a result of a guest accessing the PCI config space, so if
> the vCPU is not running defer_map() can't be called either for that
> vCPU.
Fine. So long as someone has looked into it and thinks we're fine.
~Andrew
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