Changeset 64880 in vbox

Timestamp:

Dec 15, 2016 2:53:09 PM (8 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

112287

Message:

VMM/HMVMXR0: "& 0xf" is redundant while right-shifting a uint8_t by 4 bits. Also comment clarification.

File:

• trunk/src/VBox/VMM/VMMR0/HMVMXR0.cpp (modified) (3 diffs)

trunk/src/VBox/VMM/VMMR0/HMVMXR0.cpp

@@ -3414 +3414 @@
             && APICIsEnabled(pVCpu))
         {
-            /* Setup TPR shadowing. Also setup TPR patching for 32-bit guests. */
             if (pVCpu->hm.s.vmx.u32ProcCtls & VMX_VMCS_CTRL_PROC_EXEC_USE_TPR_SHADOW)
             {
@@ -3426 +3425 @@
 
                 /*
-                 * If there are external interrupts pending but masked by the TPR value, instruct VT-x to cause a VM-exit when
-                 * the guest lowers its TPR below the highest-priority pending interrupt and we can deliver the interrupt.
-                 * If there are no external interrupts pending, set threshold to 0 to not cause a VM-exit. We will eventually deliver
-                 * the interrupt when we VM-exit for other reasons.
+                 * If there are interrupts pending but masked by the TPR, instruct VT-x to cause a TPR-below-threshold VM-exit
+                 * when the guest lowers its TPR below the priority of the pending interrupt so we can deliver the interrupt.
+                 * If there are no interrupts pending, set threshold to 0 to not cause any TPR-below-threshold VM-exits.
                  */
                 pVCpu->hm.s.vmx.pbVirtApic[XAPIC_OFF_TPR] = u8Tpr;
@@ -3436 +3434 @@
                 {
                     /* Bits 3:0 of the TPR threshold field correspond to bits 7:4 of the TPR (which is the Task-Priority Class). */
-                    const uint8_t u8PendingPriority = (u8PendingIntr >> 4) & 0xf;
-                    const uint8_t u8TprPriority     = (u8Tpr >> 4) & 0xf;
+                    const uint8_t u8PendingPriority = u8PendingIntr >> 4;
+                    const uint8_t u8TprPriority     = u8Tpr >> 4;
                     if (u8PendingPriority <= u8TprPriority)
                         u32TprThreshold = u8PendingPriority;