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

["Liu, Yi L" <yi.l.liu@intel.com>]

> From: Jason Gunthorpe <jgg@nvidia.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