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

Rafael J. Wysocki
2016-03-24T15:08:34Z

On Thu, Mar 24, 2016 at 3:44 PM, Shannon Zhao <shannon.zhao@linaro.org> 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@rjwysocki.net> (supporter:ACPI)
> CC: Len Brown <lenb@kernel.org> (supporter:ACPI)
> CC: linux-acpi@vger.kernel.org (open list:ACPI)
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> ---
> 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.
> --