linux-kernel - [PATCH 11/13] x86_64: Remove pointless set

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Message-ID: <20221022114425.168036718@infradead.org>
Date:   Sat, 22 Oct 2022 13:14:14 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, willy@...radead.org, torvalds@...ux-foundation.org,
        akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        linux-mm@...ck.org, aarcange@...hat.com,
        kirill.shutemov@...ux.intel.com, jroedel@...e.de, ubizjak@...il.com
Subject: [PATCH 11/13] x86_64: Remove pointless set_64bit() usage

The use of set_64bit() in X86_64 only code is pretty pointless, seeing
how it's a direct assignment. Remove all this nonsense.

Additionally, since x86_64 unconditionally has HAVE_CMPXCHG_DOUBLE,
there is no point in even having that fallback.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/um/include/asm/pgtable-3level.h |    8 --------
 arch/x86/include/asm/cmpxchg_64.h    |    5 -----
 drivers/iommu/intel/irq_remapping.c  |   10 ++--------
 3 files changed, 2 insertions(+), 21 deletions(-)

--- a/arch/um/include/asm/pgtable-3level.h
+++ b/arch/um/include/asm/pgtable-3level.h
@@ -58,11 +58,7 @@
 #define pud_populate(mm, pud, pmd) \
 	set_pud(pud, __pud(_PAGE_TABLE + __pa(pmd)))
 
-#ifdef CONFIG_64BIT
-#define set_pud(pudptr, pudval) set_64bit((u64 *) (pudptr), pud_val(pudval))
-#else
 #define set_pud(pudptr, pudval) (*(pudptr) = (pudval))
-#endif
 
 static inline int pgd_newpage(pgd_t pgd)
 {
@@ -71,11 +67,7 @@ static inline int pgd_newpage(pgd_t pgd)
 
 static inline void pgd_mkuptodate(pgd_t pgd) { pgd_val(pgd) &= ~_PAGE_NEWPAGE; }
 
-#ifdef CONFIG_64BIT
-#define set_pmd(pmdptr, pmdval) set_64bit((u64 *) (pmdptr), pmd_val(pmdval))
-#else
 #define set_pmd(pmdptr, pmdval) (*(pmdptr) = (pmdval))
-#endif
 
 static inline void pud_clear (pud_t *pud)
 {
--- a/arch/x86/include/asm/cmpxchg_64.h
+++ b/arch/x86/include/asm/cmpxchg_64.h
@@ -2,11 +2,6 @@
 #ifndef _ASM_X86_CMPXCHG_64_H
 #define _ASM_X86_CMPXCHG_64_H
 
-static inline void set_64bit(volatile u64 *ptr, u64 val)
-{
-	*ptr = val;
-}
-
 #define arch_cmpxchg64(ptr, o, n)					\
 ({									\
 	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
--- a/drivers/iommu/intel/irq_remapping.c
+++ b/drivers/iommu/intel/irq_remapping.c
@@ -173,7 +173,6 @@ static int modify_irte(struct irq_2_iomm
 	index = irq_iommu->irte_index + irq_iommu->sub_handle;
 	irte = &iommu->ir_table->base[index];
 
-#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE)
 	if ((irte->pst == 1) || (irte_modified->pst == 1)) {
 		bool ret;
 
@@ -187,11 +186,6 @@ static int modify_irte(struct irq_2_iomm
 		 * same as the old value.
 		 */
 		WARN_ON(!ret);
-	} else
-#endif
-	{
-		set_64bit(&irte->low, irte_modified->low);
-		set_64bit(&irte->high, irte_modified->high);
 	}
 	__iommu_flush_cache(iommu, irte, sizeof(*irte));
 
@@ -249,8 +243,8 @@ static int clear_entries(struct irq_2_io
 	end = start + (1 << irq_iommu->irte_mask);
 
 	for (entry = start; entry < end; entry++) {
-		set_64bit(&entry->low, 0);
-		set_64bit(&entry->high, 0);
+		WRITE_ONCE(entry->low, 0);
+		WRITE_ONCE(entry->high, 0);
 	}
 	bitmap_release_region(iommu->ir_table->bitmap, index,
 			      irq_iommu->irte_mask);