linux-kernel - Re: [PATCH v3 4/5] iommufd: Add replace support in iommufd_access_set

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Date:   Thu, 2 Mar 2023 15:53:08 -0800
From:   Nicolin Chen <nicolinc@...dia.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
CC:     "jgg@...dia.com" <jgg@...dia.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "will@...nel.org" <will@...nel.org>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "farman@...ux.ibm.com" <farman@...ux.ibm.com>
Subject: Re: [PATCH v3 4/5] iommufd: Add replace support in
 iommufd_access_set_ioas()

On Thu, Mar 02, 2023 at 08:23:54AM +0000, Tian, Kevin wrote:
> External email: Use caution opening links or attachments
> 
> 
> > From: Nicolin Chen <nicolinc@...dia.com>
> > Sent: Saturday, February 25, 2023 9:52 AM
> >
> > +     /*
> > +      * Set ioas to NULL to block any further iommufd_access_pin_pages().
> > +      * iommufd_access_unpin_pages() can continue using access-
> > >ioas_unpin.
> > +      */
> > +     access->ioas = NULL;
> > +
> > +     mutex_unlock(&access->ioas_lock);
> > +     access->ops->unmap(access->data, 0, ULONG_MAX);
> > +     mutex_lock(&access->ioas_lock);
> 
> This should check whether @unmap is valid.

Will change to 
+	if (access->ops->unmap) {
+		mutex_unlock(&access->ioas_lock);
+		access->ops->unmap(access->data, 0, ULONG_MAX);
+		mutex_lock(&access->ioas_lock);
+	}

Thanks!
Nic