ia32-64/x86/vmcall.html
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<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:svg="http://www.w3.org/2000/svg" xmlns:x86="http://www.felixcloutier.com/x86"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><link rel="stylesheet" type="text/css" href="style.css"></link><title>VMCALL
— Call to VM Monitor</title></head><body><header><nav><ul><li><a href='index.html'>Index</a></li><li>December 2023</li></ul></nav></header><h1>VMCALL
— Call to VM Monitor</h1>
<table>
<tr>
<th>Opcode/Instruction</th>
<th>Op/En</th>
<th>Description</th></tr>
<tr>
<td>0F 01 C1 VMCALL</td>
<td>ZO</td>
<td>Call to VM monitor by causing VM exit.</td></tr></table>
<h2 id="instruction-operand-encoding">Instruction Operand Encoding<a class="anchor" href="#instruction-operand-encoding">
</a></h2>
<table>
<tr>
<td>Op/En</td>
<td>Operand 1</td>
<td>Operand 2</td>
<td>Operand 3</td>
<td>Operand 4</td></tr>
<tr>
<td>ZO</td>
<td>NA</td>
<td>NA</td>
<td>NA</td>
<td>NA</td></tr></table>
<h2 id="description">Description<a class="anchor" href="#description">
</a></h2>
<p>This instruction allows guest software can make a call for service into an underlying VM monitor. The details of the programming interface for such calls are VMM-specific; this instruction does nothing more than cause a VM exit, registering the appropriate exit reason.</p>
<p>Use of this instruction in VMX root operation invokes an SMM monitor (see Section 32.15.2). This invocation will activate the dual-monitor treatment of system-management interrupts (SMIs) and system-management mode (SMM) if it is not already active (see Section 32.15.6).</p>
<h2 id="operation">Operation<a class="anchor" href="#operation">
</a></h2>
<pre>IF not in VMX operation
THEN #UD;
ELSIF in VMX non-root operation
THEN VM exit;
ELSIF (RFLAGS.VM = 1) or (IA32_EFER.LMA = 1 and CS.L = 0)
THEN #UD;
ELSIF CPL &gt; 0
THEN #GP(0);
ELSIF in SMM or the logical processor does not support the dual-monitor treatment of SMIs and SMM or the valid bit in the
IA32_SMM_MONITOR_CTL MSR is clear
THEN VMfail (VMCALL executed in VMX root operation);
ELSIF dual-monitor treatment of SMIs and SMM is active
THEN perform an SMM VM exit (see Section 32.15.2);
ELSIF current-VMCS pointer is not valid
THEN VMfailInvalid;
ELSIF launch state of current VMCS is not clear
THEN VMfailValid(VMCALL with non-clear VMCS);
ELSIF VM-exit control fields are not valid (see Section 32.15.6.1)
THEN VMfailValid (VMCALL with invalid VM-exit control fields);
ELSE
enter SMM;
read revision identifier in MSEG;
IF revision identifier does not match that supported by processor
THEN
leave SMM;
VMfailValid(VMCALL with incorrect MSEG revision identifier);
ELSE
read SMM-monitor features field in MSEG (see Section 32.15.6.1);
IF features field is invalid
THEN
leave SMM;
VMfailValid(VMCALL with invalid SMM-monitor features);
ELSE activate dual-monitor treatment of SMIs and SMM (see Section 32.15.6);
FI;
FI;
FI;
</pre>
<h2 id="flags-affected">Flags Affected<a class="anchor" href="#flags-affected">
</a></h2>
<p>See the operation section and Section 31.2.</p>
<h2 class="exceptions" id="protected-mode-exceptions">Protected Mode Exceptions<a class="anchor" href="#protected-mode-exceptions">
</a></h2>
<table>
<tr>
<td>#GP(0)</td>
<td>If the current privilege level is not 0 and the logical processor is in VMX root operation.</td></tr>
<tr>
<td>#UD</td>
<td>If executed outside VMX operation.</td></tr></table>
<h2 class="exceptions" id="real-address-mode-exceptions">Real-Address Mode Exceptions<a class="anchor" href="#real-address-mode-exceptions">
</a></h2>
<table>
<tr>
<td>#UD</td>
<td>If executed outside VMX operation.</td></tr></table>
<h2 class="exceptions" id="virtual-8086-mode-exceptions">Virtual-8086 Mode Exceptions<a class="anchor" href="#virtual-8086-mode-exceptions">
</a></h2>
<table>
<tr>
<td>#UD</td>
<td>If executed outside VMX non-root operation.</td></tr></table>
<h2 class="exceptions" id="compatibility-mode-exceptions">Compatibility Mode Exceptions<a class="anchor" href="#compatibility-mode-exceptions">
</a></h2>
<table>
<tr>
<td>#UD</td>
<td>If executed outside VMX non-root operation.</td></tr></table>
<h2 class="exceptions" id="64-bit-mode-exceptions">64-Bit Mode Exceptions<a class="anchor" href="#64-bit-mode-exceptions">
</a></h2>
<table>
<tr>
<td>#UD</td>
<td>If executed outside VMX operation.</td></tr></table><footer><p>
This UNOFFICIAL, mechanically-separated, non-verified reference is provided for convenience, but it may be
inc<span style="opacity: 0.2">omp</span>lete or b<sub>r</sub>oke<sub>n</sub> in various obvious or non-obvious
ways. Refer to <a href="https://software.intel.com/en-us/download/intel-64-and-ia-32-architectures-sdm-combined-volumes-1-2a-2b-2c-2d-3a-3b-3c-3d-and-4">Intel® 64 and IA-32 Architectures Software Developers Manual</a> for anything serious.
</p></footer></body></html>