Re: [Xen-devel] [PATCH v5 01/17] Xen: ACPI: Hide UART used by Xen

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 4 Mar 2016, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> 
> 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.
> 
> Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> ---
> CC: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx> (supporter:ACPI)
> CC: Len Brown <lenb@xxxxxxxxxx> (supporter:ACPI)
> CC: linux-acpi@xxxxxxxxxxxxxxx (open list:ACPI)
> ---
>  drivers/acpi/scan.c | 68 
> +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 68 insertions(+)
> 
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 407a376..31d794c 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 +1454,47 @@ static int acpi_add_single_object(struct acpi_device 
> **child,
>       return 0;
>  }
>  
> +static acpi_status acpi_get_resource_fixed_memory32(struct acpi_resource 
> *res,
> +                                                 void *context)
> +{
> +     struct acpi_resource_fixed_memory32 *fixed_memory32;
> +
> +     if (res->type != ACPI_RESOURCE_TYPE_FIXED_MEMORY32)
> +             return AE_OK;
> +
> +     fixed_memory32 = &res->data.fixed_memory32;

Should we call acpi_resource_to_address64 instead?
Aside from this the rest looks good.


> +     if (!fixed_memory32)
> +             return AE_OK;
> +
> +     *((u32 *)context) = fixed_memory32->address;
> +     return AE_CTRL_TERMINATE;
> +}
> +
> +static bool acpi_device_should_be_hidden(acpi_handle handle)
> +{
> +     acpi_status status;
> +     u32 addr = 0;
> +
> +     /* 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_fixed_memory32,
> +                                          &addr);
> +             if (ACPI_FAILURE(status))
> +                     return false;
> +
> +             if (addr == 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 +1508,9 @@ 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))
> @@ -1919,6 +1964,8 @@ static int acpi_bus_scan_fixed(void)
>  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();
> @@ -1933,6 +1980,27 @@ 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) {
> +                     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");
> +             }
> +     }
> +
>       mutex_lock(&acpi_scan_lock);
>       /*
>        * Enumerate devices in the ACPI namespace.
> -- 
> 2.0.4
> 
> 

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