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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: Adrian Catangiu <acatan@amazon.com>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	qemu-devel@nongnu.org, kvm@vger.kernel.org,
	linux-s390@vger.kernel.org, gregkh@linuxfoundation.org,
	graf@amazon.com, arnd@arndb.de, ebiederm@xmission.com,
	rppt@kernel.org, 0x7f454c46@gmail.com, borntraeger@de.ibm.com,
	Jason@zx2c4.com, jannh@google.com, w@1wt.eu, colmmacc@amazon.com,
	luto@kernel.org, tytso@mit.edu, ebiggers@kernel.org,
	dwmw@amazon.co.uk, bonzini@gnu.org, sblbir@amazon.com,
	raduweis@amazon.com, corbet@lwn.net, mhocko@kernel.org,
	rafael@kernel.org, mpe@ellerman.id.au, areber@redhat.com,
	ovzxemul@gmail.com, avagin@gmail.com, ptikhomirov@virtuozzo.com,
	gil@azul.com, asmehra@redhat.com, dgunigun@redhat.com,
	vijaysun@ca.ibm.com, oridgar@gmail.com, ghammer@redhat.com
Subject: Re: [PATCH v4 1/2] drivers/misc: sysgenid: add system generation id driver
Date: Tue, 2 Feb 2021 09:32:50 -0500	[thread overview]
Message-ID: <20210202092418-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20210127221505.GB24799@amd>

On Wed, Jan 27, 2021 at 11:15:05PM +0100, Pavel Machek wrote:
> Hi!
> 
> > - Solution
> > 
> > The System Generation ID is a simple concept meant to alleviate the
> > issue by providing a monotonically increasing u32 counter that changes
> > each time the VM or container is restored from a snapshot.
> 
> I'd make it u64.
> 
> But as people explained, this has race problems that may be impossible
> to solve?

Well the read/write interface could be used in a safe way thinkably:

- application checks VM gen id
- application sends a transaction e.g. to  database
- application re-checks VM gen id
- if id changed, application checks the database for duplicate
  transactions

not sure how can the mmap interface be used safely.
Drop it for now?



> Best regards,
> 								Pavel
> 								
> -- 
> http://www.livejournal.com/~pavelmachek



  reply	other threads:[~2021-02-02 14:35 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-12 12:15 [PATCH v4 0/2] System Generation ID driver and VMGENID backend Adrian Catangiu
2021-01-12 12:15 ` [PATCH v4 1/2] drivers/misc: sysgenid: add system generation id driver Adrian Catangiu
2021-01-12 13:08   ` Greg KH
2021-01-21  9:54     ` Catangiu, Adrian Costin
2021-01-12 13:08   ` Michael S. Tsirkin
2021-01-21 12:48     ` Catangiu, Adrian Costin
2021-01-19 22:34   ` Randy Dunlap
2021-01-27 22:15   ` Pavel Machek
2021-02-02 14:32     ` Michael S. Tsirkin [this message]
2021-01-12 12:16 ` [PATCH v4 2/2] drivers/virt: vmgenid: add vm " Adrian Catangiu
2021-01-12 12:48 ` [PATCH v4 0/2] System Generation ID driver and VMGENID backend Michael S. Tsirkin
2021-01-21 10:28   ` Catangiu, Adrian Costin
2021-01-27 12:47     ` Michael S. Tsirkin
2021-01-28 12:58       ` Alexander Graf
2021-02-02 14:34         ` Michael S. Tsirkin

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