linux-kernel - Re: [PATCH] ACPI/HMAT: Fix the parsing of Cache Associativity and Write Policy

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Date:   Tue, 10 Dec 2019 16:19:55 +0800
From:   Tao Xu <tao3.xu@...el.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI/HMAT: Fix the parsing of Cache Associativity and
 Write Policy

On 12/10/2019 4:06 PM, Rafael J. Wysocki wrote:
> On Tue, Dec 10, 2019 at 2:04 AM Tao Xu <tao3.xu@...el.com> wrote:
>>
>> On 12/9/2019 6:01 PM, Rafael J. Wysocki wrote:
>>> On Mon, Dec 2, 2019 at 8:03 AM Tao Xu <tao3.xu@...el.com> wrote:
>>>>
>>>> In chapter 5.2.27.5, Table 5-147: Field "Cache Attributes" of
>>>> ACPI 6.3 spec: 0 is "None", 1 is "Direct Mapped", 2 is "Complex Cache
>>>> Indexing" for Cache Associativity; 0 is "None", 1 is "Write Back",
>>>> 2 is "Write Through" for Write Policy.
>>>
>>> Well, I'm not sure what the connection between the above statement,
>>> which is correct AFAICS, and the changes made by the patch is.
>>>
>>> Is that the *_OTHER symbol names are confusing or something deeper?
>>>
>>
>> Because in include/acpi/actbl1.h:
>>
>> #define ACPI_HMAT_CA_NONE                     (0)
>>
>> ACPI_HMAT_CA_NONE is 0, but in include/linux/node.h:
>>
>>      enum cache_indexing {
>>             NODE_CACHE_DIRECT_MAP,
>>             NODE_CACHE_INDEXED,
>>             NODE_CACHE_OTHER,
>>      };
>> NODE_CACHE_OTHER is 2, and for otner enum:
>>
>>            case ACPI_HMAT_CA_DIRECT_MAPPED:
>>                    tcache->cache_attrs.indexing = NODE_CACHE_DIRECT_MAP;
>>                    break;
>>            case ACPI_HMAT_CA_COMPLEX_CACHE_INDEXING:
>>                    tcache->cache_attrs.indexing = NODE_CACHE_INDEXED;
>>                    break;
>> in include/acpi/actbl1.h:
>>
>>    #define ACPI_HMAT_CA_DIRECT_MAPPED            (1)
>>    #define ACPI_HMAT_CA_COMPLEX_CACHE_INDEXING   (2)
>>
>> but in include/linux/node.h:
>>
>> NODE_CACHE_DIRECT_MAP is 0, NODE_CACHE_INDEXED is 1. This is incorrect.
> 
> Why is it incorrect?

Sorry I paste the wrong pre-define.

This is the incorrect line:

case ACPI_HMAT_CA_DIRECT_MAPPED:
tcache->cache_attrs.indexing = NODE_CACHE_DIRECT_MAP;

ACPI_HMAT_CA_DIRECT_MAPPED is 1, NODE_CACHE_DIRECT_MAP is 0. That means 
if HMAT table input 1 for cache_attrs.indexing, kernel store 0 in 
cache_attrs.indexing. But in ACPI 6.3, 0 means "None". So for the whole 
switch codes:

         switch ((attrs & ACPI_HMAT_CACHE_ASSOCIATIVITY) >> 8) {
         case ACPI_HMAT_CA_DIRECT_MAPPED(1):
                 tcache->cache_attrs.indexing = NODE_CACHE_DIRECT_MAP(0);
                 break;
         case ACPI_HMAT_CA_COMPLEX_CACHE_INDEXING(2):
                 tcache->cache_attrs.indexing = NODE_CACHE_INDEXED(1);
                 break;
         case ACPI_HMAT_CA_NONE(0):
         default:
                 tcache->cache_attrs.indexing = NODE_CACHE_OTHER(2);
                 break;
         }