From: Halil Pasic <pasic@linux.ibm.com>
To: Tony Krowiak <akrowiak@linux.ibm.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>,
linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
borntraeger@de.ibm.com, cohuck@redhat.com,
pasic@linux.vnet.ibm.com, jjherne@linux.ibm.com,
alex.williamson@redhat.com, kwankhede@nvidia.com
Subject: Re: [PATCH v3 2/2] s390/vfio-ap: control access to PQAP(AQIC) interception handler
Date: Thu, 20 May 2021 10:48:57 +0200 [thread overview]
Message-ID: <20210520104857.65d75858.pasic@linux.ibm.com> (raw)
In-Reply-To: <330f099c-3d5e-c552-3047-4b462b1c9fa9@linux.ibm.com>
On Wed, 19 May 2021 21:08:15 -0400
Tony Krowiak <akrowiak@linux.ibm.com> wrote:
> >
> > This is nonesense too:
> >
> > if (vcpu->kvm->arch.crypto.pqap_hook) {
> > if (!try_module_get(vcpu->kvm->arch.crypto.pqap_hook->owner))
> > return -EOPNOTSUPP;
> > ret = vcpu->kvm->arch.crypto.pqap_hook->hook(vcpu);
> >
> > It should have a lock around it of some kind, not a
> > try_module_get. module_get is not la lock.
>
> As I said earlier, I don't know why the author did this.
Please have a look at these links from the archive to get some
perspective:
https://lkml.org/lkml/2020/12/4/994
https://lkml.org/lkml/2020/12/3/987
https://www.lkml.org/lkml/2019/3/1/260
We can ask the original author, but I don't think we have to. BTW the
patch that introduced it has your r-b.
> My best guess
> is that he wanted to ensure that the module was still loaded; otherwise,
> the data structures contained therein - for example, the pqap_hook
> and matrix_mdev that contains it - would be gonzo.
More precisely prevent the module from unloading while we execute code
from it. As I've pointed out in a previous email the module may be gone
by the time we call try_module_get().
Regards,
Halil
next prev parent reply other threads:[~2021-05-20 8:49 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-19 15:39 [PATCH v3 0/2] s390/vfio-ap: fix memory leak in mdev remove callback Tony Krowiak
2021-05-19 15:39 ` [PATCH v3 1/2] " Tony Krowiak
2021-05-19 15:39 ` [PATCH v3 2/2] s390/vfio-ap: control access to PQAP(AQIC) interception handler Tony Krowiak
2021-05-19 16:16 ` Jason Gunthorpe
2021-05-19 23:04 ` Tony Krowiak
2021-05-19 23:22 ` Jason Gunthorpe
2021-05-20 1:08 ` Tony Krowiak
2021-05-20 8:48 ` Halil Pasic [this message]
2021-05-20 12:26 ` Jason Gunthorpe
2021-05-20 8:38 ` Halil Pasic
2021-05-20 12:51 ` Jason Gunthorpe
2021-05-21 18:24 ` Tony Krowiak
2021-05-21 18:30 ` Jason Gunthorpe
2021-05-19 17:21 ` Halil Pasic
2021-05-19 23:14 ` Tony Krowiak
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