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

[Tao Xu]

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;
        }