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

Tao Xu <tao3.xu@xxxxxxxxx> · Tue, 10 Dec 2019 16:19:55 +0800

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