[PATCH v2 01/16] Xen: ACPI: Hide UART used by Xen

[PATCH v2 01/16] Xen: ACPI: Hide UART used by Xen

[Shannon Zhao]

From: Shannon Zhao <shannon.zhao@linaro.org>

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@linaro.org>
---
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)
---
 drivers/acpi/bus.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index a212cef..d7a559f 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -46,6 +46,7 @@ ACPI_MODULE_NAME("bus");
 struct acpi_device *acpi_root;
 struct proc_dir_entry *acpi_root_dir;
 EXPORT_SYMBOL(acpi_root_dir);
+static u64 spcr_uart_addr;
 
 #ifdef CONFIG_X86
 #ifdef CONFIG_ACPI_CUSTOM_DSDT
@@ -93,6 +94,17 @@ acpi_status acpi_bus_get_status_handle(acpi_handle handle,
 {
 	acpi_status status;
 
+	if (spcr_uart_addr != 0xffffffffffffffff) {
+		u64 addr;
+
+		status = acpi_evaluate_integer(handle, METHOD_NAME__ADR, NULL,
+					       &addr);
+		if (ACPI_SUCCESS(status) && (addr == spcr_uart_addr)) {
+			*sta = 0;
+			return AE_OK;
+		}
+	}
+
 	status = acpi_evaluate_integer(handle, "_STA", NULL, sta);
 	if (ACPI_SUCCESS(status))
 		return AE_OK;
@@ -1069,6 +1081,8 @@ EXPORT_SYMBOL_GPL(acpi_kobj);
 static int __init acpi_init(void)
 {
 	int result;
+	acpi_status status;
+	struct acpi_table_stao *stao_ptr;
 
 	if (acpi_disabled) {
 		printk(KERN_INFO PREFIX "Interpreter disabled.\n");
@@ -1081,6 +1095,22 @@ static int __init acpi_init(void)
 		acpi_kobj = NULL;
 	}
 
+	/* If there is STAO table, check whether it needs to ignore the UART
+	 * device in SPCR table.
+	 */
+	spcr_uart_addr = 0xffffffffffffffff;
+	status = acpi_get_table(ACPI_SIG_STAO, 0,
+				(struct acpi_table_header **)&stao_ptr);
+	if (ACPI_SUCCESS(status)) {
+		if (stao_ptr->ignore_uart) {
+			struct acpi_table_spcr *spcr_ptr;
+
+			acpi_get_table(ACPI_SIG_SPCR, 0,
+				       (struct acpi_table_header **)&spcr_ptr);
+			spcr_uart_addr = spcr_ptr->serial_port.address;
+		}
+	}
+
 	init_acpi_device_notify();
 	result = acpi_bus_init();
 	if (result) {
-- 
2.0.4

Re: [PATCH v2 01/16] Xen: ACPI: Hide UART used by Xen

[Stefano Stabellini]

On Fri, 15 Jan 2016, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> 
> 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-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> ---
> CC: "Rafael J. Wysocki" <rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org> (supporter:ACPI)
> CC: Len Brown <lenb-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> (supporter:ACPI)
> CC: linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org (open list:ACPI)
> ---
>  drivers/acpi/bus.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
> index a212cef..d7a559f 100644
> --- a/drivers/acpi/bus.c
> +++ b/drivers/acpi/bus.c
> @@ -46,6 +46,7 @@ ACPI_MODULE_NAME("bus");
>  struct acpi_device *acpi_root;
>  struct proc_dir_entry *acpi_root_dir;
>  EXPORT_SYMBOL(acpi_root_dir);
> +static u64 spcr_uart_addr;
>  
>  #ifdef CONFIG_X86
>  #ifdef CONFIG_ACPI_CUSTOM_DSDT
> @@ -93,6 +94,17 @@ acpi_status acpi_bus_get_status_handle(acpi_handle handle,
>  {
>  	acpi_status status;
>  
> +	if (spcr_uart_addr != 0xffffffffffffffff) {

Please #define something like EFI_INVALID_TABLE_ADDR and use it here
instead of 0xffffffffffffffff for readability. Also spcr_uart_addr could
be initialized where it is defined.

Maybe it could be better to move this check into a separate function and
only call acpi_set_device_status if spcr_uart_addr != addr?


> +		u64 addr;
> +
> +		status = acpi_evaluate_integer(handle, METHOD_NAME__ADR, NULL,
> +					       &addr);
> +		if (ACPI_SUCCESS(status) && (addr == spcr_uart_addr)) {
> +			*sta = 0;
> +			return AE_OK;
> +		}
> +	}
> +
>  	status = acpi_evaluate_integer(handle, "_STA", NULL, sta);
>  	if (ACPI_SUCCESS(status))
>  		return AE_OK;
> @@ -1069,6 +1081,8 @@ EXPORT_SYMBOL_GPL(acpi_kobj);
>  static int __init acpi_init(void)
>  {
>  	int result;
> +	acpi_status status;
> +	struct acpi_table_stao *stao_ptr;
>  
>  	if (acpi_disabled) {
>  		printk(KERN_INFO PREFIX "Interpreter disabled.\n");
> @@ -1081,6 +1095,22 @@ static int __init acpi_init(void)
>  		acpi_kobj = NULL;
>  	}
>  
> +	/* If there is STAO table, check whether it needs to ignore the UART
> +	 * device in SPCR table.
> +	 */
> +	spcr_uart_addr = 0xffffffffffffffff;
> +	status = acpi_get_table(ACPI_SIG_STAO, 0,
> +				(struct acpi_table_header **)&stao_ptr);
> +	if (ACPI_SUCCESS(status)) {
> +		if (stao_ptr->ignore_uart) {

if (ACPI_SUCCESS(status) && stao_ptr->ignore_uart) {


> +			struct acpi_table_spcr *spcr_ptr;
> +
> +			acpi_get_table(ACPI_SIG_SPCR, 0,
> +				       (struct acpi_table_header **)&spcr_ptr);

Maybe we should check that acpi_get_table succeeded, even though it
should at this point.


> +			spcr_uart_addr = spcr_ptr->serial_port.address;
> +		}
> +	}
> +
>  	init_acpi_device_notify();
>  	result = acpi_bus_init();
>  	if (result) {

Re: [PATCH v2 01/16] Xen: ACPI: Hide UART used by Xen

[Mark Rutland]

On Fri, Jan 15, 2016 at 02:55:14PM +0800, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> 
> 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-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> ---
> CC: "Rafael J. Wysocki" <rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org> (supporter:ACPI)
> CC: Len Brown <lenb-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> (supporter:ACPI)
> CC: linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org (open list:ACPI)
> ---
>  drivers/acpi/bus.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
> index a212cef..d7a559f 100644
> --- a/drivers/acpi/bus.c
> +++ b/drivers/acpi/bus.c
> @@ -46,6 +46,7 @@ ACPI_MODULE_NAME("bus");
>  struct acpi_device *acpi_root;
>  struct proc_dir_entry *acpi_root_dir;
>  EXPORT_SYMBOL(acpi_root_dir);
> +static u64 spcr_uart_addr;
>  
>  #ifdef CONFIG_X86
>  #ifdef CONFIG_ACPI_CUSTOM_DSDT
> @@ -93,6 +94,17 @@ acpi_status acpi_bus_get_status_handle(acpi_handle handle,
>  {
>  	acpi_status status;
>  
> +	if (spcr_uart_addr != 0xffffffffffffffff) {

The SPCR spec says that the Base Address fields being zero means that
console redirection is disabled (though I'm not clear on whether or not
that requires the whole acpi_generic_address to be zero).

Can we not use that here?

Mark.

> +		u64 addr;
> +
> +		status = acpi_evaluate_integer(handle, METHOD_NAME__ADR, NULL,
> +					       &addr);
> +		if (ACPI_SUCCESS(status) && (addr == spcr_uart_addr)) {
> +			*sta = 0;
> +			return AE_OK;
> +		}
> +	}
> +
>  	status = acpi_evaluate_integer(handle, "_STA", NULL, sta);
>  	if (ACPI_SUCCESS(status))
>  		return AE_OK;
> @@ -1069,6 +1081,8 @@ EXPORT_SYMBOL_GPL(acpi_kobj);
>  static int __init acpi_init(void)
>  {
>  	int result;
> +	acpi_status status;
> +	struct acpi_table_stao *stao_ptr;
>  
>  	if (acpi_disabled) {
>  		printk(KERN_INFO PREFIX "Interpreter disabled.\n");
> @@ -1081,6 +1095,22 @@ static int __init acpi_init(void)
>  		acpi_kobj = NULL;
>  	}
>  
> +	/* If there is STAO table, check whether it needs to ignore the UART
> +	 * device in SPCR table.
> +	 */
> +	spcr_uart_addr = 0xffffffffffffffff;
> +	status = acpi_get_table(ACPI_SIG_STAO, 0,
> +				(struct acpi_table_header **)&stao_ptr);
> +	if (ACPI_SUCCESS(status)) {
> +		if (stao_ptr->ignore_uart) {
> +			struct acpi_table_spcr *spcr_ptr;
> +
> +			acpi_get_table(ACPI_SIG_SPCR, 0,
> +				       (struct acpi_table_header **)&spcr_ptr);
> +			spcr_uart_addr = spcr_ptr->serial_port.address;
> +		}
> +	}
> +
>  	init_acpi_device_notify();
>  	result = acpi_bus_init();
>  	if (result) {
> -- 
> 2.0.4
> 
> 
> --
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Re: [PATCH v2 01/16] Xen: ACPI: Hide UART used by Xen

[Stefano Stabellini]

On Mon, 18 Jan 2016, Mark Rutland wrote:
> On Fri, Jan 15, 2016 at 02:55:14PM +0800, Shannon Zhao wrote:
> > From: Shannon Zhao <shannon.zhao-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> > 
> > 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-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> > ---
> > CC: "Rafael J. Wysocki" <rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org> (supporter:ACPI)
> > CC: Len Brown <lenb-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> (supporter:ACPI)
> > CC: linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org (open list:ACPI)
> > ---
> >  drivers/acpi/bus.c | 30 ++++++++++++++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> > 
> > diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
> > index a212cef..d7a559f 100644
> > --- a/drivers/acpi/bus.c
> > +++ b/drivers/acpi/bus.c
> > @@ -46,6 +46,7 @@ ACPI_MODULE_NAME("bus");
> >  struct acpi_device *acpi_root;
> >  struct proc_dir_entry *acpi_root_dir;
> >  EXPORT_SYMBOL(acpi_root_dir);
> > +static u64 spcr_uart_addr;
> >  
> >  #ifdef CONFIG_X86
> >  #ifdef CONFIG_ACPI_CUSTOM_DSDT
> > @@ -93,6 +94,17 @@ acpi_status acpi_bus_get_status_handle(acpi_handle handle,
> >  {
> >  	acpi_status status;
> >  
> > +	if (spcr_uart_addr != 0xffffffffffffffff) {
> 
> The SPCR spec says that the Base Address fields being zero means that
> console redirection is disabled (though I'm not clear on whether or not
> that requires the whole acpi_generic_address to be zero).
> 
> Can we not use that here?

Shannon changed the code from 0 to 0xffffffffffffffff following my
suggestion to his previous series, but I didn't realize that the SPCR
spec says 0 means no console redirection. In that case using 0 is
better.