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

Tao Xu
2019-12-10T08:19:59Z

On 12/10/2019 4:06 PM, Rafael J. Wysocki wrote:
> On Tue, Dec 10, 2019 at 2:04 AM Tao Xu <tao3.xu@intel.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@intel.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;
}