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tools: build qemu-vmsr-helper

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Introduce a privileged helper to access RAPL MSR.

The privileged helper tool, qemu-vmsr-helper, is designed to provide
virtual machines with the ability to read specific RAPL (Running Average
Power Limit) MSRs without requiring CAP_SYS_RAWIO privileges or relying
on external, out-of-tree patches.

The helper tool leverages Unix permissions and SO_PEERCRED socket
options to enforce access control, ensuring that only processes
explicitly requesting read access via readmsr() from a valid Thread ID
can access these MSRs.

The list of RAPL MSRs that are allowed to be read by the helper tool is
defined in rapl-msr-index.h. This list corresponds to the RAPL MSRs that
will be supported in the next commit titled "Add support for RAPL MSRs
in KVM/QEMU."

The tool is intentionally designed to run on the Linux x86 platform.
This initial implementation is tailored for Intel CPUs but can be
extended to support AMD CPUs in the future.

Signed-off-by: Anthony Harivel <aharivel@redhat.com>
Link: https://lore.kernel.org/r/20240522153453.1230389-3-aharivel@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Anthony Harivel 2024-05-22 17:34:51 +02:00 • committed by Paolo Bonzini
parent 95fa0c79a0
commit 84369d7621
8 changed files with 680 additions and 0 deletions
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15
contrib/systemd/qemu-vmsr-helper.service Normal file
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[Unit]
Description=Virtual RAPL MSR Daemon for QEMU
[Service]
WorkingDirectory=/tmp
Type=simple
ExecStart=/usr/bin/qemu-vmsr-helper
PrivateTmp=yes
ProtectSystem=strict
ReadWritePaths=/var/run
RestrictAddressFamilies=AF_UNIX
Restart=always
RestartSec=0
[Install]