Re: [PATCH V4 01/10] acpi: apei: read ack upon ghes record consumption

[Baicar, Tyler]

On 10/24/2016 2:51 AM, Suzuki K Poulose wrote:
> On 21/10/16 18:30, Tyler Baicar wrote:
> > 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 | 42 
> > ++++++++++++++++++++++++++++++++++++++++++
> >  drivers/acpi/apei/hest.c |  7 +++++--
> >  include/acpi/ghes.h      |  5 ++++-
> >  3 files changed, 51 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> > index 60746ef..7d020b0 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>
> > @@ -79,6 +80,10 @@
> >      ((struct acpi_hest_generic_status *)                \
> >       ((struct ghes_estatus_node *)(estatus_node) + 1))
> >
> > +#define HEST_TYPE_GENERIC_V2(ghes)                \
> > +    ((struct acpi_hest_header *)ghes->generic)->type ==    \
> > +     ACPI_HEST_TYPE_GENERIC_ERROR_V2
> > +
> >  /*
> >   * This driver isn't really modular, however for the time being,
> >   * continuing to use module_param is the easiest way to remain
> > @@ -248,7 +253,15 @@ static struct ghes *ghes_new(struct 
> > acpi_hest_generic *generic)
> >      ghes = kzalloc(sizeof(*ghes), GFP_KERNEL);
> >      if (!ghes)
> >          return ERR_PTR(-ENOMEM);
> > +
> >      ghes->generic = generic;
> > +    if (HEST_TYPE_GENERIC_V2(ghes)) {
> > +        rc = apei_map_generic_address(
> > +            &ghes->generic_v2->read_ack_register);
> > +        if (rc)
> > +            goto err_unmap;
>
> I think should be goto err_free, see more below.
>
> > +    }
> > +
> >      rc = apei_map_generic_address(&generic->error_status_address);
> >      if (rc)
> >          goto err_free;
> > @@ -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 (HEST_TYPE_GENERIC_V2(ghes))
> > +        apei_unmap_generic_address(
> > +            &ghes->generic_v2->read_ack_register);
>
> We might end up trying to unmap (error_status_address) which is not 
> mapped
> if we hit the error in mapping read_ack_register. The 
> read_ack_register unmap
> hunk should be moved below to err_free.
This needs to be changed, I'll add a separate label for unmapping 
read_ack_register and error_status_address for the case that the 
read_ack_register map succeeds but the error_status_address map fails.

err_unmap_status_addr:
apei_unmap_generic_address(&generic->error_status_address);
err_unmap_read_ack_addr:
        if (HEST_TYPE_GENERIC_V2(ghes))
                apei_unmap_generic_address(
&ghes->generic_v2->read_ack_register);
err_free:
        kfree(ghes);
        return ERR_PTR(rc);

If mapping read_ack_register fails, goto err_free.
If mapping read_ack_register is successful but mapping 
error_status_address fails, goto err_unmap_read_ack_addr.
And if both mappings succeed but the kmalloc fails, then goto 
err_unmap_status_addr.

> >  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 (HEST_TYPE_GENERIC_V2(ghes))
> > +        apei_unmap_generic_address(
> > +            &ghes->generic_v2->read_ack_register);
> >  }
> >
> >  static inline int ghes_severity(int severity)
> > @@ -648,6 +667,23 @@ static void ghes_estatus_cache_add(
> >      rcu_read_unlock();
> >  }
>
> > +static int ghes_do_read_ack(struct acpi_hest_generic_v2 *generic_v2)
>
> nit: We are actually writing something to the read_ack_register. The 
> names
> read_ack_register (which may be as per standard) and more importantly the
> function name (ghes_do_read_ack) sounds a bit misleading.
It is called "Read Ack Register" in the spec (ACPI 6.1 table 18-344), 
but I agree the function name can be improved.
Maybe ghes_acknowledge_error or ghes_ack_error.

Thanks,
Tyler
> Rest looks fine to me.
>
> Suzuki

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