Hi Denis,
On 06/06/2025 07:55, dm...@proton.me wrote:
On Thu, Jun 05, 2025 at 10:58:48PM +0100, Julien Grall wrote:
+if ( domid == DOMID_INVALID )
+panic("Error allocating ID for domain %s\n", dt_node_name(node));
+
+d = domain_create(domid, &d_cfg, flags);
if ( IS_ERR(d) )
panic("Error creating domain %s (rc = %ld)\n",
dt_node_name(node), PTR_ERR(d));
diff --git a/xen/common/domain.c b/xen/common/domain.c
index abf1969e60..ae0c44fcbb 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -66,6 +66,10 @@ DEFINE_RCU_READ_LOCK(domlist_read_lock);
static struct domain *domain_hash[DOMAIN_HASH_SIZE];
struct domain *domain_list;
+/* Non-system domain ID allocator. */
+static DEFINE_SPINLOCK(domid_lock);
+static DECLARE_BITMAP(domid_bitmap, DOMID_FIRST_RESERVED);
+
/*
* Insert a domain into the domlist/hash. This allows the domain to be
looked
* up by domid, and therefore to be the subject of hypercalls/etc.
@@ -1449,6 +1453,8 @@ void domain_destroy(struct domain *d)
TRACE_TIME(TRC_DOM0_DOM_REM, d->domain_id);
+domid_free(d->domain_id);
+
/* Remove from the domlist/hash. */
domlist_remove(d);
@@ -2405,6 +2411,54 @@ domid_t get_initial_domain_id(void)
return hardware_domid;
}
+domid_t domid_alloc(domid_t domid)
+{
+spin_lock(&domid_lock);
+
+if ( domid < DOMID_FIRST_RESERVED )
+{
+if ( __test_and_set_bit(domid, domid_bitmap) )
+domid = DOMID_INVALID;
+}
+else
+{
+static domid_t domid_last;
+/* NB: account for late hwdom case, skip ID#0 */
I am somewhat confused with this comment. For the late hwdom case, I
thought we were using a non-zero ID. Dom0 should also always be the
first dom0 to be reserved. Can you clarify?
My current understanding is:
- the ID of "domain 0" (privileged domain) can be overridden at the boot-time
via hardware_domid parameter.
> > - there's only one reserved (and configurable) domain ID ==
hardware_domid in
the allocation range (which is 0 by default).
> > - get_initial_domain_id() returns the reserved domain ID value
(which is
used in the in the follow on change to keep the change isolated).
Is my understanding correct?
I have replied yesterday night on a separate thread about this behavior
[1]. Rather than duplicating it, I would suggest to move the
conversation there.
In short, I believe the late domain support was recently broken.
Cheers,
[1]
https://lore.kernel.org/xen-devel/20250528225030.2652166-1-dmuk...@ford.com/T/#mdcdf3802a913859243ff6ce841
445cfab265145f
--
Julien Grall
