Re: [Xen-devel] [PATCH 1/2] Xen acpi pad implement

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.10.12 at 14:19, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
> --- /dev/null
> +++ b/drivers/xen/xen_acpi_pad.c
> @@ -0,0 +1,173 @@
> +/*
> + * xen_acpi_pad.c - Xen pad interface
> + *
> + * Copyright (c) 2012, Intel Corporation.
> + *    Author: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/types.h>
> +#include <acpi/acpi_bus.h>
> +#include <acpi/acpi_drivers.h>
> +#include <asm/xen/hypercall.h>
> +
> +#if defined(CONFIG_ACPI_PROCESSOR_AGGREGATOR) || \
> +             defined(CONFIG_ACPI_PROCESSOR_AGGREGATOR_MODULE)
> +
> +#define ACPI_PROCESSOR_AGGREGATOR_CLASS      "acpi_pad"
> +#define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator"
> +#define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80
> +
> +static int xen_acpi_pad_idle_cpus(int *num_cpus)
> +{
> +     int ret;
> +

Stray blank line.

> +     struct xen_platform_op op = {
> +             .cmd = XENPF_core_parking,
> +             .interface_version = XENPF_INTERFACE_VERSION,

This is redundant with HYPERVISOR_dom0_op().

> +     };
> +
> +     /* set cpu nums expected to be idled */
> +     op.u.core_parking.type = XEN_CORE_PARKING_SET;
> +     op.u.core_parking.idle_nums = (uint32_t)*num_cpus;

It is quite a bit more efficient in terms of generated code to
initialize all fields using assignments (the use of an initializer
setting only a subset of fields will cause all other fields to get
zero initialized). In any case I think it is bad style to mix both
approaches.

> +     ret = HYPERVISOR_dom0_op(&op);
> +     if (ret)
> +             return ret;
> +
> +     /*
> +      * get cpu nums actually be idled
> +      * cannot get it by using hypercall once (shared with _SET)
> +      * because of the characteristic of Xen continue_hypercall_on_cpu
> +      */
> +     op.u.core_parking.type = XEN_CORE_PARKING_GET;
> +     ret = HYPERVISOR_dom0_op(&op);
> +     if (ret)
> +             return ret;
> +
> +     *num_cpus = op.u.core_parking.idle_nums;

"num_cpus" doesn't need to be a pointer, and you don't need to
call _GET here either - callers that care for the count in effect
after the call can invoke the corresponding _GET on their own.

> +     return 0;
> +}
> +
> +/*
> + * Query firmware how many CPUs should be idle
> + * return -1 on failure
> + */
> +static int xen_acpi_pad_pur(acpi_handle handle)
> +{
> +     struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
> +     union acpi_object *package;
> +     int num = -1;
> +
> +     if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
> +             return num;
> +
> +     if (!buffer.length || !buffer.pointer)
> +             return num;
> +
> +     package = buffer.pointer;
> +
> +     if (package->type == ACPI_TYPE_PACKAGE &&
> +             package->package.count == 2 &&
> +             package->package.elements[0].integer.value == 1) /* rev 1 */
> +
> +             num = package->package.elements[1].integer.value;
> +
> +     kfree(buffer.pointer);
> +     return num;
> +}
> +
> +/* Notify firmware how many CPUs are idle */
> +static void xen_acpi_pad_ost(acpi_handle handle, int stat,
> +     uint32_t idle_cpus)
> +{
> +     union acpi_object params[3] = {
> +             {.type = ACPI_TYPE_INTEGER,},
> +             {.type = ACPI_TYPE_INTEGER,},
> +             {.type = ACPI_TYPE_BUFFER,},
> +     };
> +     struct acpi_object_list arg_list = {3, params};
> +
> +     params[0].integer.value = ACPI_PROCESSOR_AGGREGATOR_NOTIFY;
> +     params[1].integer.value =  stat;
> +     params[2].buffer.length = 4;
> +     params[2].buffer.pointer = (void *)&idle_cpus;
> +     acpi_evaluate_object(handle, "_OST", &arg_list, NULL);
> +}
> +
> +static void xen_acpi_pad_handle_notify(acpi_handle handle)
> +{
> +     int ret, num_cpus;
> +
> +     num_cpus = xen_acpi_pad_pur(handle);
> +     if (num_cpus < 0)
> +             return;
> +
> +     ret = xen_acpi_pad_idle_cpus(&num_cpus);
> +     if (ret)
> +             return;
> +
> +     xen_acpi_pad_ost(handle, 0, num_cpus);
> +}
> +
> +static void xen_acpi_pad_notify(acpi_handle handle, u32 event,
> +     void *data)
> +{
> +     switch (event) {
> +     case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
> +             xen_acpi_pad_handle_notify(handle);
> +             break;
> +     default:
> +             pr_warn("Unsupported event [0x%x]\n", event);
> +             break;
> +     }
> +}
> +
> +static int xen_acpi_pad_add(struct acpi_device *device)
> +{
> +     acpi_status status;
> +
> +     strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
> +     strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
> +
> +     status = acpi_install_notify_handler(device->handle,
> +              ACPI_DEVICE_NOTIFY, xen_acpi_pad_notify, device);
> +     if (ACPI_FAILURE(status))
> +             return -ENODEV;
> +
> +     return 0;
> +}
> +
> +static const struct acpi_device_id pad_device_ids[] = {
> +     {"ACPI000C", 0},
> +     {"", 0},
> +};
> +
> +static struct acpi_driver xen_acpi_pad_driver = {
> +     .name = "processor_aggregator",
> +     .class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
> +     .ids = pad_device_ids,
> +     .ops = {
> +             .add = xen_acpi_pad_add,

.remove?

> +     },
> +};
> +
> +static int __init xen_acpi_pad_init(void)
> +{
> +     /* Only DOM0 is responsible for Xen acpi pad */
> +     if (xen_initial_domain())
> +             return acpi_bus_register_driver(&xen_acpi_pad_driver);
> +
> +     return -ENODEV;
> +}
> +subsys_initcall(xen_acpi_pad_init);
> +
> +#endif

Overall I'd recommend taking a look at the cleaned up driver in
our kernels.

Jan

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