Fix sorting

Signed-off-by: Ludvig Liljenberg <4257730+ludfjig@users.noreply.github.com>

Author: ludfjig

src/perf.rs

@@ -307,6 +307,42 @@ fn check_prerequisites() -> Result<()> {
             );
         }
 
+        // Check for precise guest IP sampling support.
+        //
+        // Intel: Guest PEBS was introduced with Ice Lake.  Without it,
+        // `perf kvm` falls back to NMI-based sampling where the guest
+        // RIP has significant skid, making function-level attribution
+        // unreliable (see the module-level "Known issue" documentation).
+        //
+        // We read the PMU name from sysfs and check against the known
+        // set of pre-Ice-Lake PMU names (a closed set that won't grow).
+        // Unknown names are assumed to be newer and not warned about.
+        //
+        // TODO: AMD guest IBS (IBSVIRT, Zen 4+) has the same issue but
+        // detection is not implemented yet — needs testing on AMD hardware.
+        const PRE_ICELAKE_PMUS: &[&str] = &[
+            "nehalem",
+            "westmere",
+            "sandybridge",
+            "ivybridge",
+            "haswell",
+            "broadwell",
+            "skylake",
+            "knl", // Knights Landing
+        ];
+        if let Ok(pmu_name) = fs::read_to_string(
+            "/sys/bus/event_source/devices/cpu/caps/pmu_name",
+        ) {
+            let pmu = pmu_name.trim();
+            if PRE_ICELAKE_PMUS.contains(&pmu) {
+                eprintln!(
+                    "Warning: CPU PMU is '{pmu}' (pre-Ice Lake). Guest PEBS is not \
+                     available — guest IP samples will have significant NMI skid, \
+                     making function-level attribution unreliable."
+                );
+            }
+        }
+
         Ok(())
     }
 }
@@ -540,8 +576,10 @@ fn report_perf(args: &PerfArgs, kallsyms: &Path) -> Result<()> {
         args.output.as_os_str().to_owned(),
         "--stdio".into(),
         "--no-children".into(),
+        "--sort".into(),
+        "overhead".into(),
         "-F".into(),
-        "overhead,sym".into(),
+        "overhead,dso,sym".into(),
     ]);
 
     let mut child = Command::new("perf")