[xen staging] xen: add a domain unique id to each domain

[patchbot@xxxxxxx]

commit 58ba55959ae1bca0651396d0752c2076a45b5ee6
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Mon Dec 16 13:07:19 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Dec 16 13:07:19 2024 +0100

    xen: add a domain unique id to each domain
    
    Xenstore is referencing domains by their domid, but reuse of a domid
    can lead to the situation that Xenstore can't tell whether a domain
    with that domid has been deleted and created again without Xenstore
    noticing the domain is a new one now.
    
    Add a global domain creation unique id which is updated when creating
    a new domain, and store that value in struct domain of the new domain.
    The global unique id is initialized with the system time and updates
    are done via the xorshift algorithm which is used for pseudo random
    number generation, too (see https://en.wikipedia.org/wiki/Xorshift).
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
---
 xen/common/domain.c     | 27 +++++++++++++++++++++++++++
 xen/include/xen/sched.h |  3 +++
 2 files changed, 30 insertions(+)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 92263a4fbd..e33a0a5a21 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -562,6 +562,32 @@ static void _domain_destroy(struct domain *d)
     free_domain_struct(d);
 }
 
+static uint64_t get_unique_id(void)
+{
+    static uint64_t unique_id;
+    static DEFINE_SPINLOCK(lock);
+    uint64_t x;
+
+    spin_lock(&lock);
+
+    x = unique_id ? : NOW();
+
+    /*
+     * Pseudo-randomize id in order to avoid consumers relying on sequence.
+     * Randomization algorithm has a period of 2^64 - 1.
+     * Unique id is not repeatable between resets and each id has the same
+     * lifetime as the domain it is associated with.
+     */
+    x ^= x << 13;
+    x ^= x >> 7;
+    x ^= x << 17;
+    unique_id = x;
+
+    spin_unlock(&lock);
+
+    return x;
+}
+
 static int sanitise_domain_config(struct xen_domctl_createdomain *config)
 {
     bool hvm = config->flags & XEN_DOMCTL_CDF_hvm;
@@ -654,6 +680,7 @@ struct domain *domain_create(domid_t domid,
 
     /* Sort out our idea of is_system_domain(). */
     d->domain_id = domid;
+    d->unique_id = get_unique_id();
 
     /* Holding CDF_* internal flags. */
     d->cdf = flags;
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 76e39378b3..711668e028 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -370,6 +370,9 @@ struct domain
     domid_t          domain_id;
 
     unsigned int     max_vcpus;
+
+    uint64_t         unique_id;       /* Unique domain identifier */
+
     struct vcpu    **vcpu;
 
     shared_info_t   *shared_info;     /* shared data area */
--
generated by git-patchbot for /home/xen/git/xen.git#staging