Merge tag 'for-upstream' of https://gitlab.com/bonzini/qemu into staging

* target/i386/kvm: support for reading RAPL MSRs using a helper program
* hpet: emulation improvements

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# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>" [full]

* tag 'for-upstream' of https://gitlab.com/bonzini/qemu:
  hpet: avoid timer storms on periodic timers
  hpet: store full 64-bit target value of the counter
  hpet: accept 64-bit reads and writes
  hpet: place read-only bits directly in "new_val"
  hpet: remove unnecessary variable "index"
  hpet: ignore high bits of comparator in 32-bit mode
  hpet: fix and cleanup persistence of interrupt status
  Add support for RAPL MSRs in KVM/Qemu
  tools: build qemu-vmsr-helper
  qio: add support for SO_PEERCRED for socket channel
  target/i386: do not crash if microvm guest uses SGX CPUID leaves

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 90 insertions, 0 deletions

diff --git a/docs/tools/index.rst b/docs/tools/index.rst
index 8e65ce0dfc..33ad438e86 100644
--- a/docs/tools/index.rst
+++ b/docs/tools/index.rst
@@ -16,3 +16,4 @@ command line utilities and other standalone programs.
    qemu-pr-helper
    qemu-trace-stap
    virtfs-proxy-helper
+   qemu-vmsr-helper
diff --git a/docs/tools/qemu-vmsr-helper.rst b/docs/tools/qemu-vmsr-helper.rst
new file mode 100644
index 0000000000..6ec87b49d9
--- /dev/null
+++ b/docs/tools/qemu-vmsr-helper.rst
@@ -0,0 +1,89 @@
+==================================
+QEMU virtual RAPL MSR helper
+==================================
+
+Synopsis
+--------
+
+**qemu-vmsr-helper** [*OPTION*]
+
+Description
+-----------
+
+Implements the virtual RAPL MSR helper for QEMU.
+
+Accessing the RAPL (Running Average Power Limit) MSR enables the RAPL powercap
+driver to advertise and monitor the power consumption or accumulated energy
+consumption of different power domains, such as CPU packages, DRAM, and other
+components when available.
+
+However those register are accesible under priviliged access (CAP_SYS_RAWIO).
+QEMU can use an external helper to access those priviliged register.
+
+:program:`qemu-vmsr-helper` is that external helper; it creates a listener
+socket which will accept incoming connections for communication with QEMU.
+
+If you want to run VMs in a setup like this, this helper should be started as a
+system service, and you should read the QEMU manual section on "RAPL MSR
+support" to find out how to configure QEMU to connect to the socket created by
+:program:`qemu-vmsr-helper`.
+
+After connecting to the socket, :program:`qemu-vmsr-helper` can
+optionally drop root privileges, except for those capabilities that
+are needed for its operation.
+
+:program:`qemu-vmsr-helper` can also use the systemd socket activation
+protocol.  In this case, the systemd socket unit should specify a
+Unix stream socket, like this::
+
+    [Socket]
+    ListenStream=/var/run/qemu-vmsr-helper.sock
+
+Options
+-------
+
+.. program:: qemu-vmsr-helper
+
+.. option:: -d, --daemon
+
+  run in the background (and create a PID file)
+
+.. option:: -q, --quiet
+
+  decrease verbosity
+
+.. option:: -v, --verbose
+
+  increase verbosity
+
+.. option:: -f, --pidfile=PATH
+
+  PID file when running as a daemon. By default the PID file
+  is created in the system runtime state directory, for example
+  :file:`/var/run/qemu-vmsr-helper.pid`.
+
+.. option:: -k, --socket=PATH
+
+  path to the socket. By default the socket is created in
+  the system runtime state directory, for example
+  :file:`/var/run/qemu-vmsr-helper.sock`.
+
+.. option:: -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]
+
+  .. include:: ../qemu-option-trace.rst.inc
+
+.. option:: -u, --user=USER
+
+  user to drop privileges to
+
+.. option:: -g, --group=GROUP
+
+  group to drop privileges to
+
+.. option:: -h, --help
+
+  Display a help message and exit.
+
+.. option:: -V, --version
+
+  Display version information and exit.