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man: document arm64 CPUFeatures

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Signed-off-by: Emanuele Rocca <emanuele.rocca@arm.com>
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Emanuele Rocca
2026-07-10 12:02:54 +02:00
parent d518675741
commit 6f9bfb0e06
1 changed files with 25 additions and 5 deletions
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man/systemd.unit.xml
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@@ -1988,11 +1988,10 @@
<varlistentry>
<term><varname>ConditionCPUFeature=</varname></term>
<listitem><para>Verify that a given CPU feature is available via the <literal>CPUID</literal>
instruction. This condition only does something on i386 and x86-64 processors. On other
processors it is assumed that the CPU does not support the given feature. It checks the leaves
<literal>1</literal>, <literal>7</literal>, <literal>0x80000001</literal>, and
<literal>0x80000007</literal>. Valid values are:
<listitem><para>On i386 and x86-64, verify that a given CPU feature is available via the
<literal>CPUID</literal> instruction. It checks the leaves <literal>1</literal>,
<literal>7</literal>, <literal>0x80000001</literal>, and <literal>0x80000007</literal>. Valid
values are:
<literal>fpu</literal>,
<literal>vme</literal>,
<literal>de</literal>,
@@ -2045,6 +2044,27 @@
<literal>abm</literal>,
<literal>constant_tsc</literal>.</para>
<para>On arm64, valid values are the corresponding arm64 feature names,
such as
<literal>asimd</literal>,
<literal>paca</literal>,
<literal>pacg</literal>,
<literal>bti</literal>,
<literal>mte</literal>,
among others. For the full list, see the documentation on
<ulink url="https://docs.kernel.org/arch/arm64/elf_hwcaps.html">ARM64 ELF hwcaps</ulink>.</para>
<para>To avoid ambiguities in mixed-architecture fleets, the value can be prefixed
with the architecture name using the form <literal>ARCH.FEATURE</literal>. If the
architecture prefix does not match the running system, the condition evaluates
to false. For example, one can specify <literal>arm64.bti</literal> on arm64
systems to check if <literal>bti</literal> is supported. In this example,
<literal>ConditionCPUFeature=arm64.bti</literal> and
<literal>ConditionCPUFeature=bti</literal> are functionally equivalent.
See <varname>ConditionArchitecture=</varname> for valid architecture names.</para>
<para>On architectures other than x86 and arm64, it is assumed that the CPU does not support the given feature.</para>
<xi:include href="version-info.xml" xpointer="v248"/>
</listitem>
</varlistentry>