Re: [PATCH v3 03/27] KVM: VMX: Add support for the secondary VM exit controls

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On 10/21/2024 1:28 AM, Chao Gao wrote:
+	for (i = 0; i < ARRAY_SIZE(vmcs_entry_exit_triplets); i++) {
+		u32 n_ctrl = vmcs_entry_exit_triplets[i].entry_control;
+		u32 x_ctrl = vmcs_entry_exit_triplets[i].exit_control;
+		u64 x_ctrl_2 = vmcs_entry_exit_triplets[i].exit_2nd_control;
+		bool has_n = n_ctrl && ((_vmentry_control & n_ctrl) == n_ctrl);
+		bool has_x = x_ctrl && ((_vmexit_control & x_ctrl) == x_ctrl);
+		bool has_x_2 = x_ctrl_2 && ((_secondary_vmexit_control & x_ctrl_2) == x_ctrl_2);
+
+		if (x_ctrl_2) {
+			/* Only activate secondary VM exit control bit should be set */
+			if ((_vmexit_control & x_ctrl) == VM_EXIT_ACTIVATE_SECONDARY_CONTROLS) {
+				if (has_n == has_x_2)
+					continue;
+			} else {
+				/* The feature should not be supported in any control */
+				if (!has_n && !has_x && !has_x_2)
+					continue;
+			}
+		} else if (has_n == has_x) {
			continue;
+		}

-		pr_warn_once("Inconsistent VM-Entry/VM-Exit pair, entry = %x, exit = %x\n",
-			     _vmentry_control & n_ctrl, _vmexit_control & x_ctrl);
+		pr_warn_once("Inconsistent VM-Entry/VM-Exit triplet, entry = %x, exit = %x, secondary_exit = %llx\n",
+			     _vmentry_control & n_ctrl, _vmexit_control & x_ctrl,
+			     _secondary_vmexit_control & x_ctrl_2);

		if (error_on_inconsistent_vmcs_config)
			return -EIO;

		_vmentry_control &= ~n_ctrl;
		_vmexit_control &= ~x_ctrl;

w/ patch 4, VM_EXIT_ACTIVATE_SECONDARY_CONTROLS is cleared if FRED fails in the
consistent check. this means, all features in the secondary vm-exit controls
are removed. it is overkill.

Good catch!


I prefer to maintain a separate table for the secondary VM-exit controls:

  	struct {
  		u32 entry_control;
  		u64 exit2_control;
	} const vmcs_entry_exit2_pairs[] = {
		{ VM_ENTRY_LOAD_IA32_FRED, SECONDARY_VM_EXIT_SAVE_IA32_FRED |
					   SECONDARY_VM_EXIT_LOAD_IA32_FRED},
	};

	for (i = 0; i < ARRAY_SIZE(vmcs_entry_exit2_pairs); i++) {
	...
	}

Hmm, I prefer one table, as it's more straight forward.


+		_secondary_vmexit_control &= ~x_ctrl_2;
	}

	rdmsrl(MSR_IA32_VMX_BASIC, basic_msr);





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