linux-kernel - Re: [PATCH v4] virt: vmgenid: introduce driver for reinitializing RNG on VM fork

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Message-ID: <b3b9dd9b-c42c-f057-f546-3e390b50479f@amazon.com>
Date:   Fri, 25 Feb 2022 16:15:59 +0100
From:   Alexander Graf <graf@...zon.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
CC:     <kvm@...r.kernel.org>, <linux-crypto@...r.kernel.org>,
        <linux-hyperv@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <adrian@...ity.io>, <ardb@...nel.org>, <ben@...portsystems.com>,
        <berrange@...hat.com>, <colmmacc@...zon.com>,
        <decui@...rosoft.com>, <dwmw@...zon.co.uk>, <ebiggers@...nel.org>,
        <ehabkost@...hat.com>, <gregkh@...uxfoundation.org>,
        <haiyangz@...rosoft.com>, <imammedo@...hat.com>,
        <jannh@...gle.com>, <kys@...rosoft.com>, <lersek@...hat.com>,
        <linux@...inikbrodowski.net>, <mst@...hat.com>,
        <qemu-devel@...gnu.org>, <raduweis@...zon.com>,
        <sthemmin@...rosoft.com>, <tytso@....edu>, <wei.liu@...nel.org>
Subject: Re: [PATCH v4] virt: vmgenid: introduce driver for reinitializing RNG
 on VM fork


On 25.02.22 15:54, Jason A. Donenfeld wrote:
> Hi Alex,
>
> Missed this remark before:
>
> On Fri, Feb 25, 2022 at 02:57:38PM +0100, Alexander Graf wrote:
>> Please expose the vmgenid via /sysfs so that user space even remotely
>> has a chance to check if it's been cloned.
> No. Did you read the 0/2 cover letter? I'll quote it for you here:
>
>> As a side note, this series intentionally does _not_ focus on
>> notification of these events to userspace or to other kernel consumers.
>> Since these VM fork detection events first need to hit the RNG, we can
>> later talk about what sorts of notifications or mmap'd counters the RNG
>> should be making accessible to elsewhere. But that's a different sort of
>> project and ties into a lot of more complicated concerns beyond this
>> more basic patchset. So hopefully we can keep the discussion rather
>> focused here to this ACPI business.
> What about that was unclear to you?
>
> Anyway, it's a different thing that will have to be designed and
> considered carefully, and that design doesn't have a whole lot to do
> with this little driver here, except insofar as it could build on top of
> it in one way or another. Yes, it's an important thing to do. No, I'm
> not going to do it in this patch here. If you want to have a discussion
> about that, start a different thread.


I'm not talking about a notification interface - we've gone through 
great length on that one in the previous submission. What I'm more 
interested in is *any* way for user space to read the current VM Gen ID. 
The same way I'm interested to see other device attributes of my system 
through sysfs.


Alex





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