Re: [PATCH V1 6/6] acpi: apei: handle SEA notification type for ARMv8

[Baicar, Tyler]

Hello Will,

On 2/10/2016 11:03 AM, Will Deacon wrote:
> On Fri, Feb 05, 2016 at 12:13:28PM -0700, Tyler Baicar wrote:
> > ARM APEI extension proposal added SEA (Synchrounous External
> > Abort) notification type for ARMv8.
> >
> > Add a new GHES error source handling function for SEA. If an error
> > source's notification type is SEA, then this function can be registered
> > into the SEA exception handler. That way GHES will parse and report
> > SEA exceptions when they occur.
> >
> > Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@xxxxxxxxxxxxxx>
> > Signed-off-by: Tyler Baicar <tbaicar@xxxxxxxxxxxxxx>
> > Signed-off-by: Naveen Kaje <nkaje@xxxxxxxxxxxxxx>
> > ---
> >   arch/arm64/Kconfig        |  1 +
> >   drivers/acpi/apei/Kconfig | 13 ++++++++
> >   drivers/acpi/apei/ghes.c  | 83 +++++++++++++++++++++++++++++++++++++++++++++++
> >   include/acpi/actbl1.h     |  6 +++-
> >   4 files changed, 102 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index 6e4a4f4..236f398 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -6,6 +6,7 @@ config ARM64
> >   	select ACPI_REDUCED_HARDWARE_ONLY if ACPI
> >   	select ARCH_HAS_DEVMEM_IS_ALLOWED
> >   	select HAVE_ACPI_APEI if ACPI
> > +	select HAVE_ACPI_APEI_SEA if ACPI
> >   	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
> >   	select ARCH_HAS_ELF_RANDOMIZE
> >   	select ARCH_HAS_GCOV_PROFILE_ALL
> > diff --git a/drivers/acpi/apei/Kconfig b/drivers/acpi/apei/Kconfig
> > index a60bb00..bfcbb9e 100644
> > --- a/drivers/acpi/apei/Kconfig
> > +++ b/drivers/acpi/apei/Kconfig
> > @@ -7,6 +7,19 @@ config HAVE_ACPI_APEI_NMI
> >   config HAVE_ACPI_APEI_HEST_IA32
> >   	bool
> >   
> > +config HAVE_ACPI_APEI_SEA
> > +	bool "APEI Synchronous External Abort logging/recovering support"
> > +	help
> > +	  This option should be enabled if the system supports
> > +	  firmware first handling of SEA (Synchronous External Abort).
> > +	  SEA happens with certain faults of data abort or instruction
> > +	  abort synchronous exceptions on ARMv8 systems. If a system
> > +	  supports firmware first handling of SEA, the platform analyzes
> > +	  and handles hardware error notifications with SEA, and it may then
> > +	  form a HW error record for the OS to parse and handle. This
> > +	  option allows the OS to look for such HW error record, and
> > +	  take appropriate action.
> > +
> >   config ACPI_APEI
> >   	bool "ACPI Platform Error Interface (APEI)"
> >   	select MISC_FILESYSTEMS
> > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> > index 6c68100..ed64b97 100644
> > --- a/drivers/acpi/apei/ghes.c
> > +++ b/drivers/acpi/apei/ghes.c
> > @@ -50,6 +50,10 @@
> >   #include <acpi/apei.h>
> >   #include <asm/tlbflush.h>
> >   
> > +#ifdef CONFIG_HAVE_ACPI_APEI_SEA
> > +#include <asm/system_misc.h>
> > +#endif
> > +
> >   #include "apei-internal.h"
> >   
> >   #define GHES_PFX	"GHES: "
> > @@ -784,6 +788,62 @@ static struct notifier_block ghes_notifier_sci = {
> >   	.notifier_call = ghes_notify_sci,
> >   };
> >   
> > +#ifdef CONFIG_HAVE_ACPI_APEI_SEA
> > +static LIST_HEAD(ghes_sea);
> > +
> > +static int ghes_notify_sea(struct notifier_block *this,
> > +				  unsigned long event, void *data)
> > +{
> > +	struct ghes *ghes;
> > +	int ret = NOTIFY_DONE;
> > +
> > +	rcu_read_lock();
> > +	list_for_each_entry_rcu(ghes, &ghes_sea, list) {
> > +		if (!ghes_proc(ghes))
> > +			ret = NOTIFY_OK;
> > +	}
> > +	rcu_read_unlock();
> > +
> > +	return ret;
> > +}
> > +
> > +static struct notifier_block ghes_notifier_sea = {
> > +	.notifier_call = ghes_notify_sea,
> > +};
> > +
> > +static int ghes_sea_add(struct ghes *ghes)
> > +{
> > +	mutex_lock(&ghes_list_mutex);
> Can you just use spin_lock, to be consistent with our other excception
> hooks?
This mutex is being used throughout ghes.c for editing the lists, so I 
think this is the proper (or at least consistent) implementation. This 
mutex was defined specifically for editing the lists according to the 
comment above the mutex definition:

"All error sources notified with SCI shares one notifier function, so 
they need to be linked and checked one by one. This is applied to NMI 
too. RCU is used for these lists, so ghes_list_mutex is only used for 
list changing, not for traversing."

The use of this mutex is identical to the way that SCI and NMI use it 
when adding or deleting from the lists. Should I add to this comment 
that this applies to SEA as well?
> > +	if (list_empty(&ghes_sea))
> > +		sea_register_handler_chain(&ghes_notifier_sea);
> > +	list_add_rcu(&ghes->list, &ghes_sea);
> > +	mutex_unlock(&ghes_list_mutex);
> > +	return 0;
> > +}
> > +
> > +static void ghes_sea_remove(struct ghes *ghes)
> > +{
> > +	mutex_lock(&ghes_list_mutex);
> > +	list_del_rcu(&ghes->list);
> > +	if (list_empty(&ghes_sea))
> > +		sea_unregister_handler_chain(&ghes_notifier_sea);
> > +	mutex_unlock(&ghes_list_mutex);
> > +}
> > +#else /* CONFIG_HAVE_ACPI_APEI_SEA */
> > +static inline int ghes_sea_add(struct ghes *ghes)
> > +{
> > +	pr_err(GHES_PFX "ID: %d, trying to add SEA notification which is not supported\n",
> > +	       ghes->generic->header.source_id);
> > +	return -ENOTSUPP;
> > +}
> > +
> > +static inline void ghes_sea_remove(struct ghes *ghes)
> > +{
> > +	pr_err(GHES_PFX "ID: %d, trying to remove SEA notification which is not supported\n",
> > +	       ghes->generic->header.source_id);
> > +}
> Why are these getting called if !CONFIG_HAVE_ACPI_APEI_SEA?
>
> Will
Thanks,
Tyler

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