On 7/2/2021 7:28 PM, Peter Zijlstra wrote:
On Tue, Jun 22, 2021 at 05:42:51PM +0800, Zhu Lingshan wrote:
+DECLARE_STATIC_CALL(x86_guest_state, *(perf_guest_cbs->state));
+
+/*
+ * We may be running with guest PEBS events created by KVM, and the
+ * PEBS records are logged into the guest's DS and invisible to host.
+ *
+ * In the case of guest PEBS overflow, we only trigger a fake event
+ * to emulate the PEBS overflow PMI for guest PBES counters in KVM.
+ * The guest will then vm-entry and check the guest DS area to read
+ * the guest PEBS records.
+ *
+ * The contents and other behavior of the guest event do not matter.
+ */
+static void x86_pmu_handle_guest_pebs(struct pt_regs *regs,
+ struct perf_sample_data *data)
+{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+ u64 guest_pebs_idxs = cpuc->pebs_enabled & ~cpuc->intel_ctrl_host_mask;
+ struct perf_event *event = NULL;
+ unsigned int guest = 0;
+ int bit;
+
+ if (!x86_pmu.pebs_vmx || !x86_pmu.pebs_active ||
+ !(cpuc->pebs_enabled & ~cpuc->intel_ctrl_host_mask))
+ return;
+
+ guest = static_call(x86_guest_state)();
+ if (!(guest & PERF_GUEST_ACTIVE))
+ return;
I think you've got the branches the wrong way around here; nobody runs a
VM so this branch will get you out without a load.
Only if you're one of those daft people running a VM, are you interested
in any of the other conditions that are required.
Also, I think both pebs_active and pebs_vmx can he a static_branch, but
that can be done later I suppose.
Hi Peter,
If I understand this correctly, are you suggesting we put "if (!(guest &
PERF_GUEST_ACTIVE))" first because this is a lower cost branch?
Thanks,
Zhu Lingshan
