linux-kernel - RE: [RFC 00/20] Introduce /dev/iommu for userspace I/O address space management

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Date:   Wed, 22 Sep 2021 03:25:02 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "hch@....de" <hch@....de>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "jean-philippe@...aro.org" <jean-philippe@...aro.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "parav@...lanox.com" <parav@...lanox.com>,
        "lkml@...ux.net" <lkml@...ux.net>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "lushenming@...wei.com" <lushenming@...wei.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "corbet@....net" <corbet@....net>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "yi.l.liu@...ux.intel.com" <yi.l.liu@...ux.intel.com>,
        "Tian, Jun J" <jun.j.tian@...el.com>, "Wu, Hao" <hao.wu@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
        "david@...son.dropbear.id.au" <david@...son.dropbear.id.au>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>
Subject: RE: [RFC 00/20] Introduce /dev/iommu for userspace I/O address space
 management

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Tuesday, September 21, 2021 9:45 PM
> 
> On Sun, Sep 19, 2021 at 02:38:28PM +0800, Liu Yi L wrote:
> > Linux now includes multiple device-passthrough frameworks (e.g. VFIO
> and
> > vDPA) to manage secure device access from the userspace. One critical
> task
> > of those frameworks is to put the assigned device in a secure, IOMMU-
> > protected context so user-initiated DMAs are prevented from doing harm
> to
> > the rest of the system.
> 
> Some bot will probably send this too, but it has compile warnings and
> needs to be rebased to 5.15-rc1

thanks Jason, will fix the warnings. yeah, I was using 5.14 in the test, will
rebase to 5.15-rc# in next version.

Regards,
Yi Liu

> drivers/iommu/iommufd/iommufd.c:269:6: warning: variable 'ret' is used
> uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
>         if (refcount_read(&ioas->refs) > 1) {
>             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/iommu/iommufd/iommufd.c:277:9: note: uninitialized use occurs
> here
>         return ret;
>                ^~~
> drivers/iommu/iommufd/iommufd.c:269:2: note: remove the 'if' if its
> condition is always true
>         if (refcount_read(&ioas->refs) > 1) {
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/iommu/iommufd/iommufd.c:253:17: note: initialize the variable 'ret'
> to silence this warning
>         int ioasid, ret;
>                        ^
>                         = 0
> drivers/iommu/iommufd/iommufd.c:727:7: warning: variable 'ret' is used
> uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
>                 if (idev->dev == dev || idev->dev_cookie == dev_cookie) {
>                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/iommu/iommufd/iommufd.c:767:17: note: uninitialized use occurs
> here
>         return ERR_PTR(ret);
>                        ^~~
> drivers/iommu/iommufd/iommufd.c:727:3: note: remove the 'if' if its
> condition is always false
>                 if (idev->dev == dev || idev->dev_cookie == dev_cookie) {
> 
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/iommu/iommufd/iommufd.c:727:7: warning: variable 'ret' is used
> uninitialized whenever '||' condition is true [-Wsometimes-uninitialized]
>                 if (idev->dev == dev || idev->dev_cookie == dev_cookie) {
>                     ^~~~~~~~~~~~~~~~
> drivers/iommu/iommufd/iommufd.c:767:17: note: uninitialized use occurs
> here
>         return ERR_PTR(ret);
>                        ^~~
> drivers/iommu/iommufd/iommufd.c:727:7: note: remove the '||' if its
> condition is always false
>                 if (idev->dev == dev || idev->dev_cookie == dev_cookie) {
>                     ^~~~~~~~~~~~~~~~~~~
> drivers/iommu/iommufd/iommufd.c:717:9: note: initialize the variable 'ret'
> to silence this warning
>         int ret;
>                ^
>                 = 0
> 
> Jason