Re: [Xen-devel] [PATCH v7 01/17] Xen: ACPI: Hide UART used by Xen

["Rafael J. Wysocki" <rafael@xxxxxxxxxx>]

On Thu, Mar 24, 2016 at 3:44 PM, Shannon Zhao <shannon.zhao@xxxxxxxxxx> wrote:
> ACPI 6.0 introduces a new table STAO to list the devices which are used
> by Xen and can't be used by Dom0. On Xen virtual platforms, the physical
> UART is used by Xen. So here it hides UART from Dom0.
>
> CC: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx> (supporter:ACPI)
> CC: Len Brown <lenb@xxxxxxxxxx> (supporter:ACPI)
> CC: linux-acpi@xxxxxxxxxxxxxxx (open list:ACPI)
> Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> ---
>  drivers/acpi/scan.c | 68 
> +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 68 insertions(+)
>
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 5f28cf7..e96a058 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -45,6 +45,7 @@ static LIST_HEAD(acpi_scan_handlers_list);
>  DEFINE_MUTEX(acpi_device_lock);
>  LIST_HEAD(acpi_wakeup_device_list);
>  static DEFINE_MUTEX(acpi_hp_context_lock);
> +static u64 spcr_uart_addr;
>
>  struct acpi_dep_data {
>         struct list_head node;
> @@ -1453,6 +1454,41 @@ static int acpi_add_single_object(struct acpi_device 
> **child,
>         return 0;
>  }
>
> +static acpi_status acpi_get_resource_memory(struct acpi_resource *ares,
> +                                           void *context)
> +{
> +       struct resource *res = context;
> +
> +       if (acpi_dev_resource_memory(ares, res))
> +               return AE_CTRL_TERMINATE;
> +
> +       return AE_OK;
> +}
> +
> +static bool acpi_device_should_be_hidden(acpi_handle handle)
> +{
> +       acpi_status status;
> +       struct resource res;
> +
> +       /* Check if it should ignore the UART device */
> +       if (spcr_uart_addr != 0) {
> +               if (!acpi_has_method(handle, METHOD_NAME__CRS))
> +                       return false;
> +
> +               status = acpi_walk_resources(handle, METHOD_NAME__CRS,
> +                                            acpi_get_resource_memory, &res);
> +               if (ACPI_FAILURE(status))
> +                       return false;
> +
> +               if (res.start == spcr_uart_addr) {
> +                       printk(KERN_INFO PREFIX "The UART device in SPCR 
> table will be hidden\n");
> +                       return true;
> +               }
> +       }
> +
> +       return false;
> +}
> +
>  static int acpi_bus_type_and_status(acpi_handle handle, int *type,
>                                     unsigned long long *sta)
>  {
> @@ -1466,6 +1502,9 @@ static int acpi_bus_type_and_status(acpi_handle handle, 
> int *type,
>         switch (acpi_type) {
>         case ACPI_TYPE_ANY:             /* for ACPI_ROOT_OBJECT */
>         case ACPI_TYPE_DEVICE:
> +               if (acpi_device_should_be_hidden(handle))
> +                       return -ENODEV;
> +
>                 *type = ACPI_BUS_TYPE_DEVICE;
>                 status = acpi_bus_get_status_handle(handle, sta);
>                 if (ACPI_FAILURE(status))
> @@ -1916,9 +1955,24 @@ static int acpi_bus_scan_fixed(void)
>         return result < 0 ? result : 0;
>  }
>
> +static void acpi_get_spcr_uart_addr(void)

static void __init acpi_get_spcr_uart_addr(void)

I suppose?

Apart from this it looks fine.

> +{
> +       acpi_status status;
> +       struct acpi_table_spcr *spcr_ptr;
> +
> +       status = acpi_get_table(ACPI_SIG_SPCR, 0,
> +                               (struct acpi_table_header **)&spcr_ptr);
> +       if (ACPI_SUCCESS(status))
> +               spcr_uart_addr = spcr_ptr->serial_port.address;
> +       else
> +               printk(KERN_WARNING PREFIX "STAO table present, but SPCR is 
> missing\n");
> +}
> +
>  int __init acpi_scan_init(void)
>  {
>         int result;
> +       acpi_status status;
> +       struct acpi_table_stao *stao_ptr;
>
>         acpi_pci_root_init();
>         acpi_pci_link_init();
> @@ -1934,6 +1988,20 @@ int __init acpi_scan_init(void)
>
>         acpi_scan_add_handler(&generic_device_handler);
>
> +       /*
> +        * If there is STAO table, check whether it needs to ignore the UART
> +        * device in SPCR table.
> +        */
> +       status = acpi_get_table(ACPI_SIG_STAO, 0,
> +                               (struct acpi_table_header **)&stao_ptr);
> +       if (ACPI_SUCCESS(status)) {
> +               if (stao_ptr->header.length > sizeof(struct acpi_table_stao))
> +                       printk(KERN_INFO PREFIX "STAO Name List not yet 
> supported.");
> +
> +               if (stao_ptr->ignore_uart)
> +                       acpi_get_spcr_uart_addr();
> +       }
> +
>         mutex_lock(&acpi_scan_lock);
>         /*
>          * Enumerate devices in the ACPI namespace.
> --

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