Re: [PATCH v2 10/17] tools/xenstored: Read event channel from xenstored page

[Juergen Gross]

On 16.07.25 23:14, Jason Andryuk wrote:

Make introduce_domain() use an event channel from the the xenstore page.
It is only used if non-zero.  Otherwise the passed in event channel port
is used.

The is useful for a xenstored stubdom to configure domains autonomously.

Signed-off-by: Jason Andryuk <jason.andr...@amd.com>
---
  tools/xenstored/domain.c | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/tools/xenstored/domain.c b/tools/xenstored/domain.c
index e1d5e8d614..94b2a1eaa7 100644
--- a/tools/xenstored/domain.c
+++ b/tools/xenstored/domain.c
@@ -1021,9 +1021,15 @@ static struct domain *introduce_domain(const void *ctx,
                return NULL;

+               evtchn_port_t iface_port;
                interface = map_interface(domid);
                if (!interface && !restore)
                        return NULL;
+
+               iface_port = interface->evtchn_port;
+               if (iface_port)
+                       port = iface_port;
+

if (!domain->introduced) {

Any reason you introduced iface_port?

I think you could just use:

+               if (interface->evtchn_port)
+                       port = interface->evtchn_port;

In case the guest is modifying the field in parallel, it would only shoot
itself in the foot. So there is no real risk in a possible double read.


Juergen

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