linux-kernel - Re: [PATCH v2] ACPI: sysfs: Enable ACPI sysfs support for CCEL records

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Message-ID: <CAJZ5v0i5n8T5QUFZKM8M0=rKOmKFa-5Zo2DsJ_Eo89apBBEsBA@mail.gmail.com>
Date:   Wed, 22 Mar 2023 20:06:03 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Rafael J Wysocki <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ACPI: sysfs: Enable ACPI sysfs support for CCEL records

On Wed, Mar 22, 2023 at 8:00 PM Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@...ux.intel.com> wrote:
>
> Hi Rafael,
>
> On 3/22/23 11:31 AM, Rafael J. Wysocki wrote:
> > On Mon, Mar 20, 2023 at 10:21 PM Kuppuswamy Sathyanarayanan
> > <sathyanarayanan.kuppuswamy@...ux.intel.com> wrote:
> >>
> >> The Confidential Computing Event Log (CCEL) table provides the address
> >> and length of the CCEL records area in UEFI reserved memory.
> >
> > The rest of this paragraph can be omitted.
> >
> >> To access
> >> these records, userspace can use /dev/mem to retrieve them. But
> >> '/dev/mem' is not enabled on many systems for security reasons.
> >>
> >> So to allow user space access these event log records without the
> >> /dev/mem interface, add support to access it via sysfs interface. The
> >> ACPI driver has provided read only access to BERT records area via
> >> '/sys/firmware/acpi/tables/data/BERT' in sysfs. So follow the same way,
> >> and add support for /sys/firmware/acpi/tables/data/CCEL to enable
> >> read-only access to the CCEL recorids area.
> >>
> >> More details about the CCEL table can be found in ACPI specification
> >> r6.5, sec titled "CC Event Log ACPI Table".
> >
> > Please provide a proper section number here and a Link: tag pointing
> > to the relevant section of the spec (which is
> > https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#cc-event-log-acpi-table
> > I think).
> >
> >> Original-patch-by: Haibo Xu <haibo1.xu@...el.com>
> >
> > If the original patch has been signed-off by that developer, you can
> > use a Co-developed-by: along with the original S-o-b tag here.
> >
> >> [Original patch is for TDEL table, modified it for CCEL support]
> >> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> >> ---
> >>
>
> How about the following version?

Looks good to me, thanks!

> ACPI: sysfs: Enable ACPI sysfs support for CCEL records
>
> The Confidential Computing Event Log (CCEL) table provides the address
> and length of the CCEL records area in UEFI reserved memory.
>
> To allow user space access to these records, expose a sysfs interface
> similar to the BERT table.
>
> More details about the CCEL table can be found in the ACPI specification
> r6.5 [1], sec 5.2.34.
>
> Link: https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#cc-event-log-acpi-table # [1]
> Co-developed-by: Haibo Xu <haibo1.xu@...el.com>
> Signed-off-by: Haibo Xu <haibo1.xu@...el.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>
>
>
> >> Changes since v1:
> >>  * Removed unnecessary parenthesis as per Rafael's suggestion..
> >>
> >>  drivers/acpi/sysfs.c | 17 +++++++++++++++++
> >>  1 file changed, 17 insertions(+)
> >>
> >> diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
> >> index 7f4ff56c9d42..687524b50085 100644
> >> --- a/drivers/acpi/sysfs.c
> >> +++ b/drivers/acpi/sysfs.c
> >> @@ -458,11 +458,28 @@ static int acpi_bert_data_init(void *th, struct acpi_data_attr *data_attr)
> >>         return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
> >>  }
> >>
> >> +static int acpi_ccel_data_init(void *th, struct acpi_data_attr *data_attr)
> >> +{
> >> +       struct acpi_table_ccel *ccel = th;
> >> +
> >> +       if (ccel->header.length < sizeof(struct acpi_table_ccel) ||
> >> +           !ccel->log_area_start_address || !ccel->log_area_minimum_length) {
> >> +               kfree(data_attr);
> >> +               return -EINVAL;
> >> +       }
> >> +       data_attr->addr = ccel->log_area_start_address;
> >> +       data_attr->attr.size = ccel->log_area_minimum_length;
> >> +       data_attr->attr.attr.name = "CCEL";
> >> +
> >> +       return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
> >> +}
> >> +
> >>  static struct acpi_data_obj {
> >>         char *name;
> >>         int (*fn)(void *, struct acpi_data_attr *);
> >>  } acpi_data_objs[] = {
> >>         { ACPI_SIG_BERT, acpi_bert_data_init },
> >> +       { ACPI_SIG_CCEL, acpi_ccel_data_init },
> >>  };
> >>
> >>  #define NUM_ACPI_DATA_OBJS ARRAY_SIZE(acpi_data_objs)
> >> --
> >> 2.34.1
> >>
>
> --
> Sathyanarayanan Kuppuswamy
> Linux Kernel Developer