On 12/09/19 14:09, Igor Mammedov wrote:
> No functional change in practice, patch only aims to properly
> document (in spec and code) intended usage of the reserved space.
>
> The new field is to be used for 2 purposes:
> - detection of modern CPU hotplug interface using
> CPHP_GET_NEXT_CPU_WITH_EVENT_CMD command.
> procedure will be described in follow up patch:
> "acpi: cpuhp: spec: add typical usecases"
> - for returning upper 32 bits of architecture specific CPU ID,
> for new CPHP_GET_CPU_ID_CMD command added by follow up patch:
> "acpi: cpuhp: add CPHP_GET_CPU_ID_CMD command"
>
> Change is backward compatible with 4.2 and older machines, as field was
> unconditionally reserved and always returned 0x0 if modern CPU hotplug
> interface was enabled.
>
> Signed-off-by: Igor Mammedov <imamm...@redhat.com>
> ---
> docs/specs/acpi_cpu_hotplug.txt | 5 ++++-
> hw/acpi/cpu.c | 11 +++++++++++
> hw/acpi/trace-events | 1 +
> 3 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/docs/specs/acpi_cpu_hotplug.txt b/docs/specs/acpi_cpu_hotplug.txt
> index 8fb9ad2..9879f9e 100644
> --- a/docs/specs/acpi_cpu_hotplug.txt
> +++ b/docs/specs/acpi_cpu_hotplug.txt
> @@ -44,7 +44,10 @@ keeps the current value.
>
> read access:
> offset:
> - [0x0-0x3] reserved
> + [0x0-0x3] Command data 2: (DWORD access)
> + if value last stored in 'Command field':
> + 0: reads as 0x0
> + other values: reserved
> [0x4] CPU device status fields: (1 byte access)
> bits:
> 0: Device is enabled and may be used by guest
> diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
> index 87f30a3..d475c06 100644
> --- a/hw/acpi/cpu.c
> +++ b/hw/acpi/cpu.c
> @@ -12,6 +12,7 @@
> #define ACPI_CPU_FLAGS_OFFSET_RW 4
> #define ACPI_CPU_CMD_OFFSET_WR 5
> #define ACPI_CPU_CMD_DATA_OFFSET_RW 8
> +#define ACPI_CPU_CMD_DATA2_OFFSET_R 0
>
> enum {
> CPHP_GET_NEXT_CPU_WITH_EVENT_CMD = 0,
> @@ -79,6 +80,16 @@ static uint64_t cpu_hotplug_rd(void *opaque, hwaddr addr,
> unsigned size)
> }
> trace_cpuhp_acpi_read_cmd_data(cpu_st->selector, val);
> break;
> + case ACPI_CPU_CMD_DATA2_OFFSET_R:
> + switch (cpu_st->command) {
> + case CPHP_GET_NEXT_CPU_WITH_EVENT_CMD:
> + val = 0;
> + break;
> + default:
> + break;
> + }
> + trace_cpuhp_acpi_read_cmd_data2(cpu_st->selector, val);
> + break;
> default:
> break;
> }
> diff --git a/hw/acpi/trace-events b/hw/acpi/trace-events
> index 96b8273..afbc77d 100644
> --- a/hw/acpi/trace-events
> +++ b/hw/acpi/trace-events
> @@ -23,6 +23,7 @@ cpuhp_acpi_read_flags(uint32_t idx, uint8_t flags)
> "idx[0x%"PRIx32"] flags: 0x%"
> cpuhp_acpi_write_idx(uint32_t idx) "set active cpu idx: 0x%"PRIx32
> cpuhp_acpi_write_cmd(uint32_t idx, uint8_t cmd) "idx[0x%"PRIx32"] cmd:
> 0x%"PRIx8
> cpuhp_acpi_read_cmd_data(uint32_t idx, uint32_t data) "idx[0x%"PRIx32"]
> data: 0x%"PRIx32
> +cpuhp_acpi_read_cmd_data2(uint32_t idx, uint32_t data) "idx[0x%"PRIx32"]
> data: 0x%"PRIx32
> cpuhp_acpi_cpu_has_events(uint32_t idx, bool ins, bool rm) "idx[0x%"PRIx32"]
> inserting: %d, removing: %d"
> cpuhp_acpi_clear_inserting_evt(uint32_t idx) "idx[0x%"PRIx32"]"
> cpuhp_acpi_clear_remove_evt(uint32_t idx) "idx[0x%"PRIx32"]"
>
Neat. :)
Reviewed-by: Laszlo Ersek <ler...@redhat.com>
