Re: [PATCH v1 1/7] xen-block: Do not write frontend nodes

From: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	Oleksandr Tyshchenko <Oleksandr_Tyshchenko@epam.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Anthony Perard <anthony.perard@citrix.com>,
	Paul Durrant <paul@xen.org>, Kevin Wolf <kwolf@redhat.com>,
	Hanna Reitz <hreitz@redhat.com>,
	"open list:X86 Xen CPUs" <xen-devel@lists.xenproject.org>,
	"open list:Block layer core" <qemu-block@nongnu.org>
Subject: Re: [PATCH v1 1/7] xen-block: Do not write frontend nodes
Date: Tue, 14 Nov 2023 21:32:05 +0000	[thread overview]
Message-ID: <87sf5858dn.fsf@epam.com> (raw)
In-Reply-To: <81BF040F-EE19-4367-9C4F-94FF2623C75B@infradead.org>

Hi David,

David Woodhouse <dwmw2@infradead.org> writes:

> On 11 November 2023 16:51:22 GMT-05:00, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>>On 11/11/2023 8:18 pm, David Woodhouse wrote:
>>> On 11 November 2023 08:43:40 GMT-05:00, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>>>> Furthermore, the control domain doesn't always have the domid of 0.
>>>>
>>>> If qemu wants/needs to make changes like this, the control domain has to
>>>> arrange for qemu's domain to have appropriate permissions on the nodes.
>>> Right. And that's simple enough: if you are running QEMU in a
>>> domain which doesn't have permission to create the backend
>>> directory and/or the frontend nodes, don't ask it to *create*
>>> devices. In that case it is only able to connect as the backend for
>>> devices which were created *for* it by the toolstack.
>>>
>>> The criterion used in this patch series should be "did QEMU create this device, or discover it".
>>>
>>
>>Yeah, that sounds like the right approach.
>
> I think we want to kill the xen_backend_set_device() function and
> instead set the backend as a property of the XenDevice *before*
> realizing it.

Not sure that I got this. Right now device is property of
XenBackendInstance. Are you proposing to make this other way around?

Right now I am looking for a place where to store the information of
XenDevice creator. My plan was to add "found_in_xenbus" property to
XenDevice and set it in xen_backend_device_create.

-- 
WBR, Volodymyr