Document work-flows for * finding a CPU with pending 'insert/remove' event * enumerating present and possible CPUs
Signed-off-by: Igor Mammedov <imamm...@redhat.com> --- docs/specs/acpi_cpu_hotplug.txt | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/docs/specs/acpi_cpu_hotplug.txt b/docs/specs/acpi_cpu_hotplug.txt index f3c552d..58c16c6 100644 --- a/docs/specs/acpi_cpu_hotplug.txt +++ b/docs/specs/acpi_cpu_hotplug.txt @@ -64,6 +64,7 @@ write access: [0x0-0x3] CPU selector: (DWORD access) selects active CPU device. All following accesses to other registers will read/store data from/to selected CPU. + Valid values: [0 .. max_cpus) [0x4] CPU device control fields: (1 byte access) bits: 0: reserved, OSPM must clear it before writing to register. @@ -96,3 +97,31 @@ write access: ACPI_DEVICE_OST QMP event from QEMU to external applications with current values of OST event and status registers. other values: reserved + + Typical usecases: + - Get a cpu with pending event + 1. Store 0x0 to the 'CPU selector' register. + 2. Store 0x0 to the 'Command field' register. + 3. Read the 'CPU device status fields' register. + 4. If both bit#1 and bit#2 are clear in the value read, there is no CPU + with a pending event and selected CPU remains unchanged. + 5. Otherwise, read the 'Command data' register. The value read is the + selector of the CPU with the pending event (which is already + selected). + + - Enumerate CPUs present/non present CPUs + 01. Set the present CPU count to 0. + 02. Set the iterator to 0. + 03. Store 0x0 to the 'CPU selector' register, to ensure that it's in + a valid state and that access to other registers won't be ignored. + 04. Store 0x0 to the 'Command field' register to make 'Command data' + register return 'CPU selector' value of selected CPU + 05. Read the 'CPU device status fields' register. + 06. If bit#0 is set, increment the present CPU count. + 07. Increment the iterator. + 08. Store the iterator to the 'CPU selector' register. + 09. Read the 'Command data' register. + 10. If the value read is not zero, goto 05. + 11. Otherwise store 0x0 to the 'CPU selector' register, to put it + into a valid state and exit. + The iterator at this point equals "max_cpus". -- 2.7.4