Re: [PATCH v2 4/6] xen_pvdev: Do not assume Dom0 when creating a directory

[Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>]

Hi Stefano,

Stefano Stabellini <sstabellini@xxxxxxxxxx> writes:

> On Wed, 22 Nov 2023, David Woodhouse wrote:
>> On Wed, 2023-11-22 at 15:09 -0800, Stefano Stabellini wrote:
>> > On Wed, 22 Nov 2023, David Woodhouse wrote:
>> > > On Wed, 2023-11-22 at 14:29 -0800, Stefano Stabellini wrote:
>> > > > On Wed, 22 Nov 2023, Paul Durrant wrote:
>> > > > > On 21/11/2023 22:10, Volodymyr Babchuk wrote:
>> > > > > > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>> > > > > > 
>> > > > > > Instead of forcing the owner to domid 0, use XS_PRESERVE_OWNER to
>> > > > > > inherit the owner of the directory.
>> > > > > 
>> > > > > Ah... so that's why the previous patch is there.
>> > > > > 
>> > > > > This is not the right way to fix it. The QEMU Xen support is 
>> > > > > *assuming* that
>> > > > > QEMU is either running in, or emulating, dom0. In the emulation case 
>> > > > > this is
>> > > > > probably fine, but the 'real Xen' case it should be using the 
>> > > > > correct domid
>> > > > > for node creation. I guess this could either be supplied on the 
>> > > > > command line
>> > > > > or discerned by reading the local domain 'domid' node.
>> > > > 
>> > > > yes, it should be passed as command line option to QEMU
>> > > 
>> > > I'm not sure I like the idea of a command line option for something
>> > > which QEMU could discover for itself.
>> > 
>> > That's fine too. I meant to say "yes, as far as I know the toolstack
>> > passes the domid to QEMU as a command line option today".
>> 
>> The -xen-domid argument on the QEMU command line today is the *guest*
>> domain ID, not the domain ID in which QEMU itself is running.
>> 
>> Or were you thinking of something different?
>
> Ops, you are right and I understand your comment better now. The backend
> domid is not on the command line but it should be discoverable (on
> xenstore if I remember right).

Yes, it is just "~/domid". I'll add a function that reads it.

-- 
WBR, Volodymyr