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

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Message-ID: <20250905133911.GG616306@nvidia.com>
Date: Fri, 5 Sep 2025 10:39:11 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: ankita@...dia.com
Cc: alex.williamson@...hat.com, yishaih@...dia.com, skolothumtho@...dia.com,
	kevin.tian@...el.com, yi.l.liu@...el.com, zhiw@...dia.com,
	aniketa@...dia.com, cjia@...dia.com, kwankhede@...dia.com,
	targupta@...dia.com, vsethi@...dia.com, acurrid@...dia.com,
	apopple@...dia.com, jhubbard@...dia.com, danw@...dia.com,
	anuaggarwal@...dia.com, mochs@...dia.com, kjaju@...dia.com,
	dnigam@...dia.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC 10/14] vfio/nvgrace-egm: Clear Memory before handing out to
 VM

On Thu, Sep 04, 2025 at 04:08:24AM +0000, ankita@...dia.com wrote:
> From: Ankit Agrawal <ankita@...dia.com>
> 
> The EGM region is invisible to the host Linux kernel and it does not
> manage the region. The EGM module manages the EGM memory and thus is
> responsible to clear out the region before handing out to the VM.
> 
> Clear EGM region on EGM chardev open. It is possible to trigger open
> multiple times by tools such as kvmtool. Thus ensure the region is
> cleared only on the first open.

It would be cleaner not to support multi-open, why is kvmtool doing
this?

Jason