On 7/11/19 11:33 PM, Thomas Gleixner wrote:
On Thu, 11 Jul 2019, Alexandre Chartre wrote:
+/*
+ * When isolation is active, the address space doesn't necessarily map
+ * the percpu offset value (this_cpu_off) which is used to get pointers
+ * to percpu variables. So functions which can be invoked while isolation
+ * is active shouldn't be getting pointers to percpu variables (i.e. with
+ * get_cpu_var() or this_cpu_ptr()). Instead percpu variable should be
+ * directly read or written to (i.e. with this_cpu_read() or
+ * this_cpu_write()).
+ */
+
+int asi_enter(struct asi *asi)
+{
+ enum asi_session_state state;
+ struct asi *current_asi;
+ struct asi_session *asi_session;
+
+ state = this_cpu_read(cpu_asi_session.state);
+ /*
+ * We can re-enter isolation, but only with the same ASI (we don't
+ * support nesting isolation). Also, if isolation is still active,
+ * then we should be re-entering with the same task.
+ */
+ if (state == ASI_SESSION_STATE_ACTIVE) {
+ current_asi = this_cpu_read(cpu_asi_session.asi);
+ if (current_asi != asi) {
+ WARN_ON(1);
+ return -EBUSY;
+ }
+ WARN_ON(this_cpu_read(cpu_asi_session.task) != current);
+ return 0;
+ }
+
+ /* isolation is not active so we can safely access the percpu pointer */
+ asi_session = &get_cpu_var(cpu_asi_session);
get_cpu_var()?? Where is the matching put_cpu_var() ? get_cpu_var()
contains a preempt_disable ...
What's wrong with a simple this_cpu_ptr() here?
Oups, my mistake, I should be using this_cpu_ptr(). I will replace all get_cpu_var()
with this_cpu_ptr().
+void asi_exit(struct asi *asi)
+{
+ struct asi_session *asi_session;
+ enum asi_session_state asi_state;
+ unsigned long original_cr3;
+
+ asi_state = this_cpu_read(cpu_asi_session.state);
+ if (asi_state == ASI_SESSION_STATE_INACTIVE)
+ return;
+
+ /* TODO: Kick sibling hyperthread before switching to kernel cr3 */
+ original_cr3 = this_cpu_read(cpu_asi_session.original_cr3);
+ if (original_cr3)
Why would this be 0 if the session is active?
Correct, original_cr3 won't be 0. I think this is a remain from a previous version
where original_cr3 was handled differently.
+ write_cr3(original_cr3);
+
+ /* page-table was switched, we can now access the percpu pointer */
+ asi_session = &get_cpu_var(cpu_asi_session);
See above.
Will fix that.
Thanks,
alex.
+ WARN_ON(asi_session->task != current);
+ asi_session->state = ASI_SESSION_STATE_INACTIVE;
+ asi_session->asi = NULL;
+ asi_session->task = NULL;
+ asi_session->original_cr3 = 0;
+}
Thanks,
tglx
