netdev - RE: [PATCH V7 mlx5-next 15/15] vfio: Extend the device migration protocol with PRE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 23 Feb 2022 00:40:58 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     Yishai Hadas <yishaih@...dia.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "saeedm@...dia.com" <saeedm@...dia.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "leonro@...dia.com" <leonro@...dia.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "mgurtovoy@...dia.com" <mgurtovoy@...dia.com>,
        "maorg@...dia.com" <maorg@...dia.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>
Subject: RE: [PATCH V7 mlx5-next 15/15] vfio: Extend the device migration
 protocol with PRE_COPY

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Tuesday, February 22, 2022 11:51 PM
> 
> On Tue, Feb 22, 2022 at 01:43:13AM +0000, Tian, Kevin wrote:
> 
> > > > > + * Drivers should attempt to return estimates so that initial_bytes +
> > > > > + * dirty_bytes matches the amount of data an immediate transition
> to
> > > > > STOP_COPY
> > > > > + * will require to be streamed.
> > > >
> > > > I didn't understand this requirement. In an immediate transition to
> > > > STOP_COPY I expect the amount of data covers the entire device
> > > > state, i.e. initial_bytes. dirty_bytes are dynamic and iteratively returned
> > > > then why we need set some expectation on the sum of
> > > > initial+round1_dity+round2_dirty+...
> > >
> > > "will require to be streamed" means additional data from this point
> > > forward, not including anything already sent.
> > >
> > > It turns into the estimate of how long STOP_COPY will take.
> >
> > I still didn't get the 'match' part. Why should the amount of data which
> > has already been sent match the additional data to be sent in STOP_COPY?
> 
> None of it is 'already been sent' the return values are always 'still
> to be sent'
> 

Reread the description:

+ * Drivers should attempt to return estimates so that initial_bytes +
+ * dirty_bytes matches the amount of data an immediate transition to STOP_COPY
+ * will require to be streamed.

I guess you intended to mean that when EITHER initial_bytes OR
dirty_bytes is read the returned value should match the amount 
of data as described above. It is "+" which confused me to think 
it as a sum of both numbers...

Thanks
Kevin