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

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Date:   Thu, 13 Apr 2017 13:45:26 -0600
From:   "Baicar, Tyler" <tbaicar@...eaurora.org>
To:     Borislav Petkov <bp@...en8.de>
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 4/11/2017 11:15 AM, Borislav Petkov wrote:
> 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().
Hello Boris,

Thank you for the feedback. I will make this change in the next version.
>> @@ -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);
> }
I will make this change in the next version.

Thanks,
Tyler
>> +	rc = apei_write(val, &generic_v2->read_ack_register);
>> +
>> +	return rc;
>> +}
>> +
>>   static int ghes_proc(struct ghes *ghes)
>>   {
>>   	int rc;

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