On 12/04/19 18:05, Igor Mammedov wrote:
> Document work-flows for
> * finding a CPU with pending 'insert/remove' event
> * enumerating present and possible CPUs
>
> Signed-off-by: Igor Mammedov <imammedo@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".
>
Nice!
I suggest unindenting the entire new text, to the leftmost column
(column#0) in the text file. Otherwise "Typical usecases" falls under
the scope of "write access".
With that:
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Thanks!
Laszlo