[xen staging] x86/HVM: limit upcall vector related verbosity

[patchbot@xxxxxxx]

commit 164daecb1834b1de5f5943abf2a0806d49470986
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Feb 26 16:03:44 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Feb 26 16:03:44 2024 +0100

    x86/HVM: limit upcall vector related verbosity
    
    Avoid logging all-identical messages for every vCPU, but make sure to
    log unusual events like the vector differing from vCPU 0's (note that
    the respective condition also makes sure vCPU 0 itself will have the
    vector setting logged), or it changing after it was once set. (Arguably
    a downside is that some vCPU not having its vector set would no longer
    be recognizable from the logs. But I think that's tolerable as
    sufficiently unlikely outside of people actively fiddling with related
    code.)
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 0cb822a41c..87d33d116b 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4125,7 +4125,15 @@ static int hvmop_set_evtchn_upcall_vector(
     if ( (v = domain_vcpu(d, op.vcpu)) == NULL )
         return -ENOENT;
 
-    printk(XENLOG_G_INFO "%pv: upcall vector %02x\n", v, op.vector);
+    /*
+     * Avoid logging all-identical messages for every vCPU, but make sure to
+     * log unusual events like the vector differing from vCPU 0's, or it
+     * changing after it was once set
+     */
+    if ( op.vector != d->vcpu[0]->arch.hvm.evtchn_upcall_vector ||
+         (v->arch.hvm.evtchn_upcall_vector &&
+          op.vector != v->arch.hvm.evtchn_upcall_vector) )
+        printk(XENLOG_G_INFO "%pv: upcall vector %02x\n", v, op.vector);
 
     v->arch.hvm.evtchn_upcall_vector = op.vector;
     hvm_assert_evtchn_irq(v);
--
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