On 22/03/2024 3:17 am, Yamahata, Isaku wrote:
+
+ for_each_online_cpu(i) {
+ int pkg = topology_physical_package_id(i);
+
+ if (cpumask_test_and_set_cpu(pkg, packages))
+ continue;
+
+ /*
+ * Program the memory controller in the package with an
+ * encryption key associated to a TDX private host key id
+ * assigned to this TDR. Concurrent operations on same memory
+ * controller results in TDX_OPERAND_BUSY. Avoid this race by
+ * mutex.
+ */
+ mutex_lock(&tdx_mng_key_config_lock[pkg]);
the lock is superfluous to me. with cpu lock held, even if multiple CPUs try to
create TDs, the same set of CPUs (the first online CPU of each package) will be
selected to configure the key because of the cpumask_test_and_set_cpu() above.
it means, we never have two CPUs in the same socket trying to program the key,
i.e., no concurrent calls.
Makes sense. Will drop the lock.
Hmm.. Skipping in cpumask_test_and_set_cpu() would result in the second
TDH.MNG.KEY.CONFIG not being done for the second VM. No?
