linux-kernel - Re: [PATCH] vfio: Reuse file f

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Message-ID: <20240627124209.GK2494510@nvidia.com>
Date: Thu, 27 Jun 2024 09:42:09 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Yan Zhao <yan.y.zhao@...el.com>
Cc: "Tian, Kevin" <kevin.tian@...el.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"alex.williamson@...hat.com" <alex.williamson@...hat.com>,
	"peterx@...hat.com" <peterx@...hat.com>,
	"ajones@...tanamicro.com" <ajones@...tanamicro.com>
Subject: Re: [PATCH] vfio: Reuse file f_inode as vfio device inode

On Thu, Jun 27, 2024 at 05:51:01PM +0800, Yan Zhao wrote:

> > > > This doesn't seem right.. There is only one device but multiple file
> > > > can be opened on that device.
> Maybe we can put this assignment to vfio_df_ioctl_bind_iommufd() after
> vfio_df_open() makes sure device->open_count is 1.

Yeah, that seems better.

Logically it would be best if all places set the inode once the
inode/FD has been made to be the one and only way to access it.

> BTW, in group path, what's the benefit of allowing multiple open of device?

I don't know, the thing that opened the first FD can just dup it, no
idea why two different FDs would be useful. It is something we removed
in the cdev flow

Jason