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<section id="acrn-cpuid-bits">
<h1>ACRN CPUID bits<a class="headerlink" href="#acrn-cpuid-bits" title="Link to this heading">¶</a></h1>
<p>A guest VM running on an ACRN hypervisor can check some of its features using
CPUID.</p>
<p>ACRN cpuid functions are:</p>
<p>function: 0x40000000</p>
<p>returns:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>eax = 0x40000010
ebx = 0x4e524341
ecx = 0x4e524341
edx = 0x4e524341
</pre></div>
</div>
<p>Note that this value in ebx, ecx and edx corresponds to the string
“ACRNACRNACRN”. The value in eax corresponds to the maximum cpuid function
present in this leaf, and will be updated if more functions are added in the
future.</p>
<p>function: define ACRN_CPUID_FEATURES (0x40000001)</p>
<p>returns:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>ebx, ecx, edx
eax = an OR'ed group of (1 << flag)
</pre></div>
</div>
<p>where <code class="docutils literal notranslate"><span class="pre">flag</span></code> is defined as below:</p>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>flag</p></th>
<th class="head"><p>value</p></th>
<th class="head"><p>meaning</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>ACRN_FEATURE_PRIVILEGED_VM</p></td>
<td><p>0</p></td>
<td><p>guest VM is a privileged VM</p></td>
</tr>
</tbody>
</table>
<p>function: 0x40000010</p>
<p>returns:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>ebx, ecx, edx
eax = (Virtual) TSC frequency in kHz.
</pre></div>
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