linux-kernel - Re: [PATCH V14 01/10] acpi: apei: read ack upon ghes record consumption

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Date:   Tue, 11 Apr 2017 19:15:47 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tyler Baicar <tbaicar@...eaurora.org>
Cc:     christoffer.dall@...aro.org, marc.zyngier@....com,
        pbonzini@...hat.com, rkrcmar@...hat.com, linux@...linux.org.uk,
        catalin.marinas@....com, will.deacon@....com, rjw@...ysocki.net,
        lenb@...nel.org, matt@...eblueprint.co.uk, robert.moore@...el.com,
        lv.zheng@...el.com, nkaje@...eaurora.org, zjzhang@...eaurora.org,
        mark.rutland@....com, james.morse@....com,
        akpm@...ux-foundation.org, eun.taik.lee@...sung.com,
        sandeepa.s.prabhu@...il.com, labbott@...hat.com,
        shijie.huang@....com, rruigrok@...eaurora.org,
        paul.gortmaker@...driver.com, tn@...ihalf.com, fu.wei@...aro.org,
        rostedt@...dmis.org, bristot@...hat.com,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-efi@...r.kernel.org,
        devel@...ica.org, Suzuki.Poulose@....com, punit.agrawal@....com,
        astone@...hat.com, harba@...eaurora.org, hanjun.guo@...aro.org,
        john.garry@...wei.com, shiju.jose@...wei.com, joe@...ches.com,
        gengdongjiu@...wei.com, xiexiuqi@...wei.com
Subject: Re: [PATCH V14 01/10] acpi: apei: read ack upon ghes record
 consumption

On Tue, Mar 28, 2017 at 01:30:31PM -0600, 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.
> 
> Add support for parsing of GHESv2 sub-tables as well.
> 
> Signed-off-by: Tyler Baicar <tbaicar@...eaurora.org>
> CC: Jonathan (Zhixiong) Zhang <zjzhang@...eaurora.org>
> Reviewed-by: James Morse <james.morse@....com>
> ---
>  drivers/acpi/apei/ghes.c | 49 +++++++++++++++++++++++++++++++++++++++++++++---
>  drivers/acpi/apei/hest.c |  7 +++++--
>  include/acpi/ghes.h      |  5 ++++-
>  3 files changed, 55 insertions(+), 6 deletions(-)

...

> @@ -249,10 +254,18 @@ 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 (IS_HEST_TYPE_GENERIC_V2(ghes)) {
> +		rc = apei_map_generic_address(
> +			&ghes->generic_v2->read_ack_register);

Yeah, that linebreak just to keep the 80-cols rule makes the code ugly
and hard to read.

Please put that mapping and unmapping in wrappers called
map_gen_v2(ghes) and unmap_gen_v2(ghes) or so, so that you can call them
wherever needed. Thus should make the flow a bit more understandable
what's going on and you won't have to repeat the unmapping lines in
ghes_fini().

> @@ -649,6 +669,23 @@ static void ghes_estatus_cache_add(
>  	rcu_read_unlock();
>  }
>  
> +static int ghes_ack_error(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 <<
> +		generic_v2->read_ack_register.bit_offset;

Yeah, let them stick out, it more readable this way. Line spacing is
helpful too:

...
        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    << generic_v2->read_ack_register.bit_offset;

        return apei_write(val, &generic_v2->read_ack_register);
}

> +	rc = apei_write(val, &generic_v2->read_ack_register);
> +
> +	return rc;
> +}
> +
>  static int ghes_proc(struct ghes *ghes)
>  {
>  	int rc;
-- 
Regards/Gruss,
    Boris.

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