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From:   Long Li <longli@microsoft.com>
To:     vkuznets <vkuznets@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC:     Bart Van Assche <bvanassche@acm.org>,
        "longli@linuxonhyperv.com" <longli@linuxonhyperv.com>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Hans de Goede <hdegoede@redhat.com>,
        "Williams, Dan J" <dan.j.williams@intel.com>,
        Maximilian Luz <luzmaximilian@gmail.com>,
        Mike Rapoport <rppt@kernel.org>,
        Ben Widawsky <ben.widawsky@intel.com>,
        Jiri Slaby <jirislaby@kernel.org>,
        Andra Paraschiv <andraprs@amazon.com>,
        Siddharth Gupta <sidgup@codeaurora.org>,
        Hannes Reinecke <hare@suse.de>
Subject: RE: [Patch v5 0/3] Introduce a driver to support host accelerated
 access to Microsoft Azure Blob for Azure VM
Thread-Topic: [Patch v5 0/3] Introduce a driver to support host accelerated
 access to Microsoft Azure Blob for Azure VM
Thread-Index: AQHXiceSNIn8c8rqq0aMs/Uc2xnVEKtlJaUAgAARXqCAAAZzgIADIFJggAC3SwCAAv3hYIBE4/SggAyEiKCAAJ8QAIAKHh2wgADF34CAAFhQAIAFJJ+w
Date:   Mon, 11 Oct 2021 17:46:48 +0000
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> Subject: Re: [Patch v5 0/3] Introduce a driver to support host accelerate=
d access
> to Microsoft Azure Blob for Azure VM
>=20
> Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:
>=20
> ...
> >
> > Not to mention the whole crazy idea of "let's implement our REST api
> > that used to go over a network connection over an ioctl instead!"
> > That's the main problem that you need to push back on here.
> >
> > What is forcing you to put all of this into the kernel in the first
> > place?  What's wrong with the userspace network connection/protocol
> > that you have today?
> >
> > Does this mean that we now have to implement all REST apis that people
> > dream up as ioctl interfaces over a hyperv transport?  That would be
> > insane.
>=20
> As far as I understand, the purpose of the driver is to replace a "slow"
> network connection to API endpoint with a "fast" transport over Vmbus. So
> what if instead of implementing this new driver we just use Hyper-V Vsock=
 and
> move API endpoint to the host?

Hi Vitaly,

We looked at Hyper-V Vsock when designing this driver. The problem is that =
the Hyper-V device model of Vsock can't support the data throughput and sca=
le needed for Blobs. Vsock is mostly used for management tasks.

The usage of Blob in Azure justifies an dedicated VMBUS channel (and sub-ch=
annels) for a new VSP/VSC driver.

Thanks,

Long

>=20
> --
> Vitaly