linux-kernel - RE: [RFC 10/14] vfio/nvgrace-egm: Clear Memory before handing out to VM

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Message-ID:
 <CH3PR12MB754873BDB6510A889170A0B3AB15A@CH3PR12MB7548.namprd12.prod.outlook.com>
Date: Mon, 15 Sep 2025 08:45:47 +0000
From: Shameer Kolothum <skolothumtho@...dia.com>
To: Ankit Agrawal <ankita@...dia.com>, Jason Gunthorpe <jgg@...dia.com>,
	"alex.williamson@...hat.com" <alex.williamson@...hat.com>, Yishai Hadas
	<yishaih@...dia.com>, "kevin.tian@...el.com" <kevin.tian@...el.com>,
	"yi.l.liu@...el.com" <yi.l.liu@...el.com>, Zhi Wang <zhiw@...dia.com>
CC: Aniket Agashe <aniketa@...dia.com>, Neo Jia <cjia@...dia.com>, Kirti
 Wankhede <kwankhede@...dia.com>, "Tarun Gupta (SW-GPU)"
	<targupta@...dia.com>, Vikram Sethi <vsethi@...dia.com>, Andy Currid
	<ACurrid@...dia.com>, Alistair Popple <apopple@...dia.com>, John Hubbard
	<jhubbard@...dia.com>, Dan Williams <danw@...dia.com>, "Anuj Aggarwal
 (SW-GPU)" <anuaggarwal@...dia.com>, Matt Ochs <mochs@...dia.com>, Krishnakant
 Jaju <kjaju@...dia.com>, Dheeraj Nigam <dnigam@...dia.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [RFC 10/14] vfio/nvgrace-egm: Clear Memory before handing out to
 VM



> -----Original Message-----
> From: Ankit Agrawal <ankita@...dia.com>
> Sent: 04 September 2025 05:08
> To: Ankit Agrawal <ankita@...dia.com>; Jason Gunthorpe <jgg@...dia.com>;
> alex.williamson@...hat.com; Yishai Hadas <yishaih@...dia.com>; Shameer
> Kolothum <skolothumtho@...dia.com>; kevin.tian@...el.com;
> yi.l.liu@...el.com; Zhi Wang <zhiw@...dia.com>
> Cc: Aniket Agashe <aniketa@...dia.com>; Neo Jia <cjia@...dia.com>; Kirti
> Wankhede <kwankhede@...dia.com>; Tarun Gupta (SW-GPU)
> <targupta@...dia.com>; Vikram Sethi <vsethi@...dia.com>; Andy Currid
> <acurrid@...dia.com>; Alistair Popple <apopple@...dia.com>; John Hubbard
> <jhubbard@...dia.com>; Dan Williams <danw@...dia.com>; Anuj Aggarwal
> (SW-GPU) <anuaggarwal@...dia.com>; Matt Ochs <mochs@...dia.com>;
> Krishnakant Jaju <kjaju@...dia.com>; Dheeraj Nigam <dnigam@...dia.com>;
> kvm@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: [RFC 10/14] vfio/nvgrace-egm: Clear Memory before handing out to
> VM
> 

[...]

>  static struct nvgrace_egm_dev *
> @@ -30,6 +31,26 @@ static int nvgrace_egm_open(struct inode *inode,
> struct file *file)
>  {
>  	struct chardev *egm_chardev =
>  		container_of(inode->i_cdev, struct chardev, cdev);
> +	struct nvgrace_egm_dev *egm_dev =
> +		egm_chardev_to_nvgrace_egm_dev(egm_chardev);
> +	void *memaddr;
> +
> +	if (atomic_inc_return(&egm_chardev->open_count) > 1)
> +		return 0;
> +
> +	/*
> +	 * nvgrace-egm module is responsible to manage the EGM memory as
> +	 * the host kernel has no knowledge of it. Clear the region before
> +	 * handing over to userspace.
> +	 */
> +	memaddr = memremap(egm_dev->egmphys, egm_dev->egmlength,
> MEMREMAP_WB);
> +	if (!memaddr) {
> +		atomic_dec(&egm_chardev->open_count);
> +		return -EINVAL;

Nit: may be better to ret -ENOMEM here.

Thanks,
Shameer