hv: allow guest with the highest severity to read RESET_CNT

Guest VM, such as Linux, may read platform RESET_CNT(0xCF9) register before writing to, in this case, ACRN should not always return dummy value. Tracked-On: projectacrn#8688 Signed-off-by: Yonghua Huang <[email protected]> Reviewed-by: Junjie Mao <[email protected]>
yonghuah · Aug 9, 2024 · 2ade211 · 2ade211
1 parent 5c351be
commit 2ade211
Showing 1 changed file with 6 additions and 2 deletions.
diff --git a/hypervisor/arch/x86/guest/vm_reset.c b/hypervisor/arch/x86/guest/vm_reset.c
@@ -74,12 +74,16 @@ static bool handle_reset_reg_read(struct acrn_vcpu *vcpu, __unused uint16_t addr
 {
 	bool ret = true;
 
-	if (is_postlaunched_vm(vcpu->vm)) {
+	if (get_highest_severity_vm(true) == vcpu->vm) {
+		/* Guest may read RESET_CONTROL register before cold reset or warm reset */
+		vcpu->req.reqs.pio_request.value = pio_read8(0xcf9U);
+
+	} else if (is_postlaunched_vm(vcpu->vm)) {
 		/* re-inject to DM */
 		ret = false;
 	} else {
 		/*
-		 * - reset control register 0xcf9: hide this from guests for now.
+		 * - reset control register 0xcf9: hide this from guests whose severity is not the highest.
 		 * - FADT reset register: the read behavior is not defined in spec, keep it simple to return all '1'.
 		 */
 		vcpu->req.reqs.pio_request.value = ~0U;