[PATCH 02/13] x86/mm/pae: Make pmd_t similar to pte_t

Peter Zijlstra
2022-10-22T11:49:51Z

Instead of mucking about with at least 2 different ways of fudging
it, do the same thing we do for pte_t.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/pgtable-3level.h | 42 +++++++++-------------------
arch/x86/include/asm/pgtable-3level_types.h | 7 ++++
arch/x86/include/asm/pgtable_64_types.h | 1
arch/x86/include/asm/pgtable_types.h | 4 --
4 files changed, 23 insertions(+), 31 deletions(-)

--- a/arch/x86/include/asm/pgtable-3level.h
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -87,7 +87,7 @@ static inline pmd_t pmd_read_atomic(pmd_
ret |= ((pmdval_t)*(tmp + 1)) << 32;
}

- return (pmd_t) { ret };
+ return (pmd_t) { .pmd = ret };
}

static inline void native_set_pte_atomic(pte_t *ptep, pte_t pte)
@@ -121,12 +121,11 @@ static inline void native_pte_clear(stru
ptep->pte_high = 0;
}

-static inline void native_pmd_clear(pmd_t *pmd)
+static inline void native_pmd_clear(pmd_t *pmdp)
{
- u32 *tmp = (u32 *)pmd;
- *tmp = 0;
+ pmdp->pmd_low = 0;
smp_wmb();
- *(tmp + 1) = 0;
+ pmdp->pmd_high = 0;
}

static inline void native_pud_clear(pud_t *pudp)
@@ -162,25 +161,17 @@ static inline pte_t native_ptep_get_and_
#define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
#endif

-union split_pmd {
- struct {
- u32 pmd_low;
- u32 pmd_high;
- };
- pmd_t pmd;
-};
-
#ifdef CONFIG_SMP
static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
{
- union split_pmd res, *orig = (union split_pmd *)pmdp;
+ pmd_t res;

/* xchg acts as a barrier before setting of the high bits */
- res.pmd_low = xchg(&orig->pmd_low, 0);
- res.pmd_high = orig->pmd_high;
- orig->pmd_high = 0;
+ res.pmd_low = xchg(&pmdp->pmd_low, 0);
+ res.pmd_high = READ_ONCE(pmdp->pmd_high);
+ WRITE_ONCE(pmdp->pmd_high, 0);

- return res.pmd;
+ return res;
}
#else
#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
@@ -199,17 +190,12 @@ static inline pmd_t pmdp_establish(struc
* anybody.
*/
if (!(pmd_val(pmd) & _PAGE_PRESENT)) {
- union split_pmd old, new, *ptr;
-
- ptr = (union split_pmd *)pmdp;
-
- new.pmd = pmd;
-
/* xchg acts as a barrier before setting of the high bits */
- old.pmd_low = xchg(&ptr->pmd_low, new.pmd_low);
- old.pmd_high = ptr->pmd_high;
- ptr->pmd_high = new.pmd_high;
- return old.pmd;
+ old.pmd_low = xchg(&pmdp->pmd_low, pmd.pmd_low);
+ old.pmd_high = READ_ONCE(pmdp->pmd_high);
+ WRITE_ONCE(pmdp->pmd_high, pmd.pmd_high);
+
+ return old;
}

do {
--- a/arch/x86/include/asm/pgtable-3level_types.h
+++ b/arch/x86/include/asm/pgtable-3level_types.h
@@ -18,6 +18,13 @@ typedef union {
};
pteval_t pte;
} pte_t;
+
+typedef union {
+ struct {
+ unsigned long pmd_low, pmd_high;
+ };
+ pmdval_t pmd;
+} pmd_t;
#endif /* !__ASSEMBLY__ */

#define SHARED_KERNEL_PMD (!static_cpu_has(X86_FEATURE_PTI))
--- a/arch/x86/include/asm/pgtable_64_types.h
+++ b/arch/x86/include/asm/pgtable_64_types.h
@@ -19,6 +19,7 @@ typedef unsigned long pgdval_t;
typedef unsigned long pgprotval_t;

typedef struct { pteval_t pte; } pte_t;
+typedef struct { pmdval_t pmd; } pmd_t;

#ifdef CONFIG_X86_5LEVEL
extern unsigned int __pgtable_l5_enabled;
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -381,11 +381,9 @@ static inline pudval_t native_pud_val(pu
#endif

#if CONFIG_PGTABLE_LEVELS > 2
-typedef struct { pmdval_t pmd; } pmd_t;
-
static inline pmd_t native_make_pmd(pmdval_t val)
{
- return (pmd_t) { val };
+ return (pmd_t) { .pmd = val };
}

static inline pmdval_t native_pmd_val(pmd_t pmd)