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x86: PAT: make pat_x_mtrr_type() more readable 

Clean up over-complications in pat_x_mtrr_type().
And if reserve_memtype() ignores stray req_type bits when
pat_enabled, it's better to mask them off when not also.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Hugh Dickins 2008-06-16 18:42:43 +01:00 committed by Ingo Molnar
parent faeca31d06
commit 6cf514fce1
1 changed files with 12 additions and 35 deletions
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47
arch/x86/mm/pat.c
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@ -159,47 +159,31 @@ static DEFINE_SPINLOCK(memtype_lock); /* protects memtype list */
* The intersection is based on "Effective Memory Type" tables in IA-32
* SDM vol 3a
*/
static int pat_x_mtrr_type(u64 start, u64 end, unsigned long prot,
unsigned long *ret_prot)
static unsigned long pat_x_mtrr_type(u64 start, u64 end, unsigned long req_type)
{
unsigned long pat_type;
u8 mtrr_type;
pat_type = prot & _PAGE_CACHE_MASK;
prot &= (~_PAGE_CACHE_MASK);
/*
* We return the PAT request directly for types where PAT takes
* precedence with respect to MTRR and for UC_MINUS.
* Consistency checks with other PAT requests is done later
* while going through memtype list.
*/
if (pat_type == _PAGE_CACHE_WC) {
*ret_prot = prot | _PAGE_CACHE_WC;
return 0;
} else if (pat_type == _PAGE_CACHE_UC_MINUS) {
*ret_prot = prot | _PAGE_CACHE_UC_MINUS;
return 0;
} else if (pat_type == _PAGE_CACHE_UC) {
*ret_prot = prot | _PAGE_CACHE_UC;
return 0;
}
if (req_type == _PAGE_CACHE_WC ||
req_type == _PAGE_CACHE_UC_MINUS ||
req_type == _PAGE_CACHE_UC)
return req_type;
/*
* Look for MTRR hint to get the effective type in case where PAT
* request is for WB.
*/
mtrr_type = mtrr_type_lookup(start, end);
if (mtrr_type == MTRR_TYPE_UNCACHABLE) {
*ret_prot = prot | _PAGE_CACHE_UC;
} else if (mtrr_type == MTRR_TYPE_WRCOMB) {
*ret_prot = prot | _PAGE_CACHE_WC;
} else {
*ret_prot = prot | _PAGE_CACHE_WB;
}
return 0;
if (mtrr_type == MTRR_TYPE_UNCACHABLE)
return _PAGE_CACHE_UC;
if (mtrr_type == MTRR_TYPE_WRCOMB)
return _PAGE_CACHE_WC;
return _PAGE_CACHE_WB;
}
/*
@ -232,7 +216,7 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
if (req_type == -1) {
*ret_type = _PAGE_CACHE_WB;
} else {
*ret_type = req_type;
*ret_type = req_type & _PAGE_CACHE_MASK;
}
}
return 0;
@ -264,14 +248,7 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
}
} else {
req_type &= _PAGE_CACHE_MASK;
err = pat_x_mtrr_type(start, end, req_type, &actual_type);
}
if (err) {
if (ret_type)
*ret_type = actual_type;
return -EINVAL;
actual_type = pat_x_mtrr_type(start, end, req_type);
}
new_entry = kmalloc(sizeof(struct memtype), GFP_KERNEL);