Re: [PATCH v2 2/6] xen: backends: touch some XenStore nodes only if device...

[Philippe Mathieu-Daudé]

Hi Volodymyr,

On 21/11/23 23:10, Volodymyr Babchuk wrote:
> was created by QEMU

Please do not split lines between subject and content. Rewrite the
full line. Preferably restrict the subject to 72 chars. Otherwise
your patch isn't displayed correctly in git tools.

Thanks,

Phil.

> Xen PV devices in QEMU can be created in two ways: either by QEMU
> itself, if they were passed via command line, or by Xen toolstack. In
> the latter case, QEMU scans XenStore entries and configures devices
> accordingly.
>
> In the second case we don't want QEMU to write/delete front-end
> entries for two reasons: it might have no access to those entries if
> it is running in un-privileged domain and it is just incorrect to
> overwrite entries already provided by Xen toolstack, because toolstack
> manages those nodes. For example, it might read backend- or frontend-
> state to be sure that they are both disconnected and it is safe to
> destroy a domain.
>
> This patch checks presence of xendev->backend to check if Xen PV
> device is acting as a backend (i.e. it was configured by Xen
> toolstack) to decide if it should touch frontend entries in XenStore.
> Also, when we need to remove XenStore entries during device teardown
> only if they weren't created by Xen toolstack. If they were created by
> toolstack, then it is toolstack's job to do proper clean-up.
>
> Suggested-by: Paul Durrant <xadimgnik@gmail.com>
> Suggested-by: David Woodhouse <dwmw@amazon.co.uk>
> Co-Authored-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
> ---
>   hw/block/xen-block.c  | 16 +++++++++-------
>   hw/char/xen_console.c |  2 +-
>   hw/net/xen_nic.c      | 18 ++++++++++--------
>   hw/xen/xen-bus.c      | 14 +++++++++-----
>   4 files changed, 29 insertions(+), 21 deletions(-)