Re: [PATCH] bus/pci: don't open uio device in secondary process

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 9 Oct 2024 12:11:32 +0200
Konrad Sztyber <konrad.sztyber@intel.com> wrote:

> On 10/7/24 19:49, Stephen Hemminger wrote:
> > On Wed, 28 Aug 2024 12:40:02 +0200
> > Konrad Sztyber <konrad.sztyber@intel.com> wrote:
> >   
> >> The uio_pci_generic driver clears the bus master bit when the device
> >> file is closed.  So, when the secondary process terminates after probing
> >> a device, that device becomes unusable in the primary process.
> >>
> >> To avoid that, the device file is now opened only in the primary
> >> process.  The commit that introduced this regression, 847d78fb95
> >> ("bus/pci: fix FD in secondary process"), only mentioned enabling access
> >> to config space from secondary process, which still works, as it doesn't
> >> rely on the device file.
> >>
> >> Fixes: 847d78fb95 ("bus/pci: fix FD in secondary process")
> >>
> >> Signed-off-by: Konrad Sztyber <konrad.sztyber@intel.com>  
> > 
> > Wouldn't this break use of interrupts in the secondary process?  
> 
> Yes, it will. But I don't think we can support interrupts in the 
> secondary process *and*, at the same time, keep the device usable in the 
> primary process when secondary terminates. Maybe we could pass the fd 
> via SCM_RIGHTS? But I don't know if that results in the same struct file 
> being used by both processes.

That is what tap, and xdp are doing.