Re: [PATCH V3 01/10] acpi: apei: read ack upon ghes record consumption

[Baicar, Tyler]

Hello Punit,

Thank you for the feedback! Responses below

On 10/12/2016 9:39 AM, Punit Agrawal wrote:
> Hi Tyler,
>
> A few comments below.
>
> Tyler Baicar <tbaicar@xxxxxxxxxxxxxx> writes:
>
> > A RAS (Reliability, Availability, Serviceability) controller
> > may be a separate processor running in parallel with OS
> > execution, and may generate error records for consumption by
> > the OS. If the RAS controller produces multiple error records,
> > then they may be overwritten before the OS has consumed them.
> >
> > The Generic Hardware Error Source (GHES) v2 structure
> > introduces the capability for the OS to acknowledge the
> > consumption of the error record generated by the RAS
> > controller. A RAS controller supporting GHESv2 shall wait for
> > the acknowledgment before writing a new error record, thus
> > eliminating the race condition.
> >
> > Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@xxxxxxxxxxxxxx>
> > Signed-off-by: Richard Ruigrok <rruigrok@xxxxxxxxxxxxxx>
> > Signed-off-by: Tyler Baicar <tbaicar@xxxxxxxxxxxxxx>
> > Signed-off-by: Naveen Kaje <nkaje@xxxxxxxxxxxxxx>
> > ---
> >   drivers/acpi/apei/ghes.c | 41 +++++++++++++++++++++++++++++++++++++++++
> >   drivers/acpi/apei/hest.c |  7 +++++--
> >   include/acpi/ghes.h      |  1 +
> >   3 files changed, 47 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> > index 60746ef..3021f0e 100644
> > --- a/drivers/acpi/apei/ghes.c
> > +++ b/drivers/acpi/apei/ghes.c
> > @@ -45,6 +45,7 @@
> >   #include <linux/aer.h>
> >   #include <linux/nmi.h>
> >   
> > +#include <acpi/actbl1.h>
> >   #include <acpi/ghes.h>
> >   #include <acpi/apei.h>
> >   #include <asm/tlbflush.h>
> > @@ -244,10 +245,22 @@ static struct ghes *ghes_new(struct acpi_hest_generic *generic)
> >   	struct ghes *ghes;
> >   	unsigned int error_block_length;
> >   	int rc;
> > +	struct acpi_hest_header *hest_hdr;
> >   
> >   	ghes = kzalloc(sizeof(*ghes), GFP_KERNEL);
> >   	if (!ghes)
> >   		return ERR_PTR(-ENOMEM);
> > +
> > +	hest_hdr = (struct acpi_hest_header *)generic;
> > +	if (hest_hdr->type == ACPI_HEST_TYPE_GENERIC_ERROR_V2) {
> > +		ghes->generic_v2 = (struct acpi_hest_generic_v2 *)generic;
> > +		rc = apei_map_generic_address(
> > +			&ghes->generic_v2->read_ack_register);
> > +		if (rc)
> > +			goto err_unmap;
> > +	} else
> > +		ghes->generic_v2 = NULL;
> Since you kzalloc ghes, shouldn't ghes->generic_v2 be NULL already?
Yes, the documentation says kzalloc returns memory set to zero, so I 
will remove this else statement.
> > +
> >   	ghes->generic = generic;
> >   	rc = apei_map_generic_address(&generic->error_status_address);
> >   	if (rc)
> > @@ -270,6 +283,9 @@ static struct ghes *ghes_new(struct acpi_hest_generic *generic)
> >   
> >   err_unmap:
> >   	apei_unmap_generic_address(&generic->error_status_address);
> > +	if (ghes->generic_v2)
> > +		apei_unmap_generic_address(
> > +			&ghes->generic_v2->read_ack_register);
> >   err_free:
> >   	kfree(ghes);
> >   	return ERR_PTR(rc);
> > @@ -279,6 +295,9 @@ static void ghes_fini(struct ghes *ghes)
> >   {
> >   	kfree(ghes->estatus);
> >   	apei_unmap_generic_address(&ghes->generic->error_status_address);
> > +	if (ghes->generic_v2)
> > +		apei_unmap_generic_address(
> > +			&ghes->generic_v2->read_ack_register);
> >   }
> >   
> >   static inline int ghes_severity(int severity)
> > @@ -648,6 +667,22 @@ static void ghes_estatus_cache_add(
> >   	rcu_read_unlock();
> >   }
> >   
> > +static int ghes_do_read_ack(struct acpi_hest_generic_v2 *generic_v2)
> > +{
> > +	int rc;
> > +	u64 val = 0;
> > +
> > +	rc = apei_read(&val, &generic_v2->read_ack_register);
> > +	if (rc)
> > +		return rc;
> > +	val &= generic_v2->read_ack_preserve <<
> > +		generic_v2->read_ack_register.bit_offset;
> > +	val |= generic_v2->read_ack_write;
> Reading the spec, it is not clear whether you need the left shift
> above.
>
> Having said that, if you do it for read_ack_preserve, do you also need
> to left shift read_ack_write by read_ack_register.bit_offset?
Good catch, it looks like the read_ack_write should also get this shift. 
I'm using a shift of 0 so I didn't catch this in testing :)
> > +	rc = apei_write(val, &generic_v2->read_ack_register);
> > +
> > +	return rc;
> > +}
> > +
> >   static int ghes_proc(struct ghes *ghes)
> >   {
> >   	int rc;
> > @@ -660,6 +695,12 @@ static int ghes_proc(struct ghes *ghes)
> >   			ghes_estatus_cache_add(ghes->generic, ghes->estatus);
> >   	}
> >   	ghes_do_proc(ghes, ghes->estatus);
> > +
> > +	if (ghes->generic_v2) {
> > +		rc = ghes_do_read_ack(ghes->generic_v2);
> > +		if (rc)
> > +			return rc;
> > +	}
> >   out:
> >   	ghes_clear_estatus(ghes);
> >   	return 0;
> > diff --git a/drivers/acpi/apei/hest.c b/drivers/acpi/apei/hest.c
> > index 792a0d9..ef725a9 100644
> > --- a/drivers/acpi/apei/hest.c
> > +++ b/drivers/acpi/apei/hest.c
> > @@ -52,6 +52,7 @@ static const int hest_esrc_len_tab[ACPI_HEST_TYPE_RESERVED] = {
> >   	[ACPI_HEST_TYPE_AER_ENDPOINT] = sizeof(struct acpi_hest_aer),
> >   	[ACPI_HEST_TYPE_AER_BRIDGE] = sizeof(struct acpi_hest_aer_bridge),
> >   	[ACPI_HEST_TYPE_GENERIC_ERROR] = sizeof(struct acpi_hest_generic),
> > +	[ACPI_HEST_TYPE_GENERIC_ERROR_V2] = sizeof(struct acpi_hest_generic_v2),
> >   };
> >   
> >   static int hest_esrc_len(struct acpi_hest_header *hest_hdr)
> > @@ -146,7 +147,8 @@ static int __init hest_parse_ghes_count(struct acpi_hest_header *hest_hdr, void
> >   {
> >   	int *count = data;
> >   
> > -	if (hest_hdr->type == ACPI_HEST_TYPE_GENERIC_ERROR)
> > +	if (hest_hdr->type == ACPI_HEST_TYPE_GENERIC_ERROR ||
> > +	    hest_hdr->type == ACPI_HEST_TYPE_GENERIC_ERROR_V2)
> >   		(*count)++;
> >   	return 0;
> >   }
> > @@ -157,7 +159,8 @@ static int __init hest_parse_ghes(struct acpi_hest_header *hest_hdr, void *data)
> >   	struct ghes_arr *ghes_arr = data;
> >   	int rc, i;
> >   
> > -	if (hest_hdr->type != ACPI_HEST_TYPE_GENERIC_ERROR)
> > +	if (hest_hdr->type != ACPI_HEST_TYPE_GENERIC_ERROR &&
> > +	    hest_hdr->type != ACPI_HEST_TYPE_GENERIC_ERROR_V2)
> >   		return 0;
> >   
> >   	if (!((struct acpi_hest_generic *)hest_hdr)->enabled)
> > diff --git a/include/acpi/ghes.h b/include/acpi/ghes.h
> > index 720446c..d0108b6 100644
> > --- a/include/acpi/ghes.h
> > +++ b/include/acpi/ghes.h
> > @@ -14,6 +14,7 @@
> >   
> >   struct ghes {
> >   	struct acpi_hest_generic *generic;
> > +	struct acpi_hest_generic_v2 *generic_v2;
> You either have a GHES or a GHESv2 structure. Instead of duplication,
> could this be represented as a union?
>
> Thanks,
> Punit
I think that should be doable. I'll make these changes in the next version.

Thanks,
Tyler
> >   	struct acpi_hest_generic_status *estatus;
> >   	u64 buffer_paddr;
> >   	unsigned long flags;

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