write in 30M

hc

2024-02-20 ea08eeccae9297f7aabd2ef7f0c2517ac4549acc

 kernel/arch/arc/mm/highmem.c
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@@ -36,8 +36,9 @@
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  *   This means each only has 1 PGDIR_SIZE worth of kvaddr mappings, which means
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  *   2M of kvaddr space for typical config (8K page and 11:8:13 traversal split)
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  *
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- * - The fixed KMAP slots for kmap_local/atomic() require KM_MAX_IDX slots per
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- *   CPU. So the number of CPUs sharing a single PTE page is limited.
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+ * - fixmap anyhow needs a limited number of mappings. So 2M kvaddr == 256 PTE
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+ *   slots across NR_CPUS would be more than sufficient (generic code defines
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+ *   KM_TYPE_NR as 20).
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  *
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  * - pkmap being preemptible, in theory could do with more than 256 concurrent
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  *   mappings. However, generic pkmap code: map_new_virtual(), doesn't traverse
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@@ -46,6 +47,48 @@
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  */
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 extern pte_t * pkmap_page_table;
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+static pte_t * fixmap_page_table;
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+
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+void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
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+{
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+	int idx, cpu_idx;
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+	unsigned long vaddr;
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+
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+	cpu_idx = kmap_atomic_idx_push();
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+	idx = cpu_idx + KM_TYPE_NR * smp_processor_id();
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+	vaddr = FIXMAP_ADDR(idx);
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+
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+	set_pte_at(&init_mm, vaddr, fixmap_page_table + idx,
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+		   mk_pte(page, prot));
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+
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+	return (void *)vaddr;
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+}
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+EXPORT_SYMBOL(kmap_atomic_high_prot);
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+
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+void kunmap_atomic_high(void *kv)
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+{
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+	unsigned long kvaddr = (unsigned long)kv;
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+
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+	if (kvaddr >= FIXMAP_BASE && kvaddr < (FIXMAP_BASE + FIXMAP_SIZE)) {
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+
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+		/*
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+		 * Because preemption is disabled, this vaddr can be associated
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+		 * with the current allocated index.
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+		 * But in case of multiple live kmap_atomic(), it still relies on
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+		 * callers to unmap in right order.
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+		 */
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+		int cpu_idx = kmap_atomic_idx();
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+		int idx = cpu_idx + KM_TYPE_NR * smp_processor_id();
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+
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+		WARN_ON(kvaddr != FIXMAP_ADDR(idx));
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+
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+		pte_clear(&init_mm, kvaddr, fixmap_page_table + idx);
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+		local_flush_tlb_kernel_range(kvaddr, kvaddr + PAGE_SIZE);
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+
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+		kmap_atomic_idx_pop();
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+	}
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+}
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+EXPORT_SYMBOL(kunmap_atomic_high);
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 static noinline pte_t * __init alloc_kmap_pgtable(unsigned long kvaddr)
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 {
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@@ -65,9 +108,10 @@
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 {
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 	/* Due to recursive include hell, we can't do this in processor.h */
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 	BUILD_BUG_ON(PAGE_OFFSET < (VMALLOC_END + FIXMAP_SIZE + PKMAP_SIZE));
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-	BUILD_BUG_ON(LAST_PKMAP > PTRS_PER_PTE);
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-	BUILD_BUG_ON(FIX_KMAP_SLOTS > PTRS_PER_PTE);
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111
 
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+	BUILD_BUG_ON(KM_TYPE_NR > PTRS_PER_PTE);
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 	pkmap_page_table = alloc_kmap_pgtable(PKMAP_BASE);
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-	alloc_kmap_pgtable(FIXMAP_BASE);
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+
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+	BUILD_BUG_ON(LAST_PKMAP > PTRS_PER_PTE);
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+	fixmap_page_table = alloc_kmap_pgtable(FIXMAP_BASE);
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 }