diff options
| author | Igor Mammedov <imammedo@redhat.com> | 2019-12-09 14:08:57 +0100 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2020-01-22 00:23:07 -0500 |
| commit | 1d7a52835dc6bf5d641a0d29ad35c881b8d0ba5a (patch) | |
| tree | 1a086130153a15eb753106a198c35b132a5fab13 /docs/specs | |
| parent | 0cdd3eae15964ab589977a09a9765d5a5ca5b9cd (diff) | |
acpi: cpuhp: spec: clarify 'CPU selector' register usage and endianness
* Move reserved registers to the top of the section, so reader would be
aware of effects when reading registers description.
* State registers endianness explicitly at the beginning of the section
* Describe registers behavior in case of 'CPU selector' register contains
value that doesn't point to a possible CPU.
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <1575896942-331151-5-git-send-email-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'docs/specs')
| -rw-r--r-- | docs/specs/acpi_cpu_hotplug.txt | 18 |
1 files changed, 12 insertions, 6 deletions
diff --git a/docs/specs/acpi_cpu_hotplug.txt b/docs/specs/acpi_cpu_hotplug.txt index ee219c8358..4e65286ff5 100644 --- a/docs/specs/acpi_cpu_hotplug.txt +++ b/docs/specs/acpi_cpu_hotplug.txt @@ -30,6 +30,18 @@ Register block base address: Register block size: ACPI_CPU_HOTPLUG_REG_LEN = 12 +All accesses to registers described below, imply little-endian byte order. + +Reserved resisters behavior: + - write accesses are ignored + - read accesses return all bits set to 0. + +The last stored value in 'CPU selector' must refer to a possible CPU, otherwise + - reads from any register return 0 + - writes to any other register are ignored until valid value is stored into it +On QEMU start, 'CPU selector' is initialized to a valid value, on reset it +keeps the current value. + read access: offset: [0x0-0x3] reserved @@ -86,9 +98,3 @@ write access: ACPI_DEVICE_OST QMP event from QEMU to external applications with current values of OST event and status registers. other values: reserved - -Selecting CPU device beyond possible range has no effect on platform: - - write accesses to CPU hot-plug registers not documented above are - ignored - - read accesses to CPU hot-plug registers not documented above return - all bits set to 0. |