The branch main has been updated by royger:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=1797ff962769aac6822cde45719ed02c18d6cdb8

commit 1797ff962769aac6822cde45719ed02c18d6cdb8
Author:     Elliott Mitchell <[email protected]>
AuthorDate: 2021-06-06 00:43:13 +0000
Commit:     Roger Pau Monné <[email protected]>
CommitDate: 2023-03-29 07:51:41 +0000

    xen/intr: cleanup event channel number use
    
    Consistently use ~0 instead of 0 when clearing xenisrc structures.
    0 is a valid event channel number, even though it is reserved by Xen.
    Whereas ~0 is guaranteed invalid.
    
    Reviewed by: royger
    MFC after: 1 week
    Differential Revision: https://reviews.freebsd.org/D30743
---
 sys/x86/xen/xen_intr.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/sys/x86/xen/xen_intr.c b/sys/x86/xen/xen_intr.c
index 4e16778874b5..3a053b10f915 100644
--- a/sys/x86/xen/xen_intr.c
+++ b/sys/x86/xen/xen_intr.c
@@ -117,9 +117,8 @@ DPCPU_DEFINE_STATIC(struct xen_intr_pcpu_data, 
xen_intr_pcpu) = {
 
 DPCPU_DECLARE(struct vcpu_info *, vcpu_info);
 
-#define        XEN_INVALID_EVTCHN      0 /* Invalid event channel */
-
-#define        is_valid_evtchn(x)      ((x) != XEN_INVALID_EVTCHN)
+#define        INVALID_EVTCHN          (~(evtchn_port_t)0) /* Invalid event 
channel */
+#define        is_valid_evtchn(x)      ((uintmax_t)(x) < NR_EVENT_CHANNELS)
 
 struct xenisrc {
        struct intsrc   xi_intsrc;
@@ -372,7 +371,7 @@ xen_intr_release_isrc(struct xenisrc *isrc)
        }
        isrc->xi_cpu = 0;
        isrc->xi_type = EVTCHN_TYPE_UNBOUND;
-       isrc->xi_port = 0;
+       isrc->xi_port = INVALID_EVTCHN;
        isrc->xi_cookie = NULL;
        mtx_unlock(&xen_intr_isrc_lock);
        return (0);
@@ -613,6 +612,19 @@ xen_intr_init(void *dummy __unused)
        if (!xen_domain())
                return (0);
 
+       _Static_assert(is_valid_evtchn(0),
+           "is_valid_evtchn(0) fails (unused by Xen, but valid by interface");
+       _Static_assert(is_valid_evtchn(NR_EVENT_CHANNELS - 1),
+           "is_valid_evtchn(max) fails (is a valid channel)");
+       _Static_assert(!is_valid_evtchn(NR_EVENT_CHANNELS),
+           "is_valid_evtchn(>max) fails (NOT a valid channel)");
+       _Static_assert(!is_valid_evtchn(~(evtchn_port_t)0),
+           "is_valid_evtchn(maxint) fails (overflow?)");
+       _Static_assert(!is_valid_evtchn(INVALID_EVTCHN),
+           "is_valid_evtchn(INVALID_EVTCHN) fails (must be invalid!)");
+       _Static_assert(!is_valid_evtchn(-1),
+           "is_valid_evtchn(-1) fails (negative are invalid)");
+
        mtx_init(&xen_intr_isrc_lock, "xen-irq-lock", NULL, MTX_DEF);
 
        /*
@@ -769,7 +781,7 @@ xen_intr_resume(struct pic *unused, bool suspend_cancelled)
                vector = first_evtchn_irq + isrc_idx;
                isrc = (struct xenisrc *)intr_lookup_source(vector);
                if (isrc != NULL) {
-                       isrc->xi_port = 0;
+                       isrc->xi_port = INVALID_EVTCHN;
                        switch (isrc->xi_type) {
                        case EVTCHN_TYPE_IPI:
                                xen_rebind_ipi(isrc);
@@ -1292,7 +1304,7 @@ int
 xen_intr_get_evtchn_from_port(evtchn_port_t port, xen_intr_handle_t *handlep)
 {
 
-       if (!is_valid_evtchn(port) || port >= NR_EVENT_CHANNELS)
+       if (!is_valid_evtchn(port))
                return (EINVAL);
 
        if (handlep == NULL) {

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