1 files changed, 346 insertions, 0 deletions
diff --git a/arch/sparc/mm/gup.c b/arch/sparc/mm/gup.c
new file mode 100644
index 000000000..f291d34a1
--- /dev/null
+++ b/arch/sparc/mm/gup.c
@@ -0,0 +1,346 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Lockless get_user_pages_fast for sparc, cribbed from powerpc
+ *
+ * Copyright (C) 2008 Nick Piggin
+ * Copyright (C) 2008 Novell Inc.
+ */
+
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/vmstat.h>
+#include <linux/pagemap.h>
+#include <linux/rwsem.h>
+#include <asm/pgtable.h>
+#include <asm/adi.h>
+
+/*
+ * The performance critical leaf functions are made noinline otherwise gcc
+ * inlines everything into a single function which results in too much
+ * register pressure.
+ */
+static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
+		unsigned long end, int write, struct page **pages, int *nr)
+{
+	unsigned long mask, result;
+	pte_t *ptep;
+
+	if (tlb_type == hypervisor) {
+		result = _PAGE_PRESENT_4V|_PAGE_P_4V;
+		if (write)
+			result |= _PAGE_WRITE_4V;
+	} else {
+		result = _PAGE_PRESENT_4U|_PAGE_P_4U;
+		if (write)
+			result |= _PAGE_WRITE_4U;
+	}
+	mask = result | _PAGE_SPECIAL;
+
+	ptep = pte_offset_kernel(&pmd, addr);
+	do {
+		struct page *page, *head;
+		pte_t pte = *ptep;
+
+		if ((pte_val(pte) & mask) != result)
+			return 0;
+		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
+
+		/* The hugepage case is simplified on sparc64 because
+		 * we encode the sub-page pfn offsets into the
+		 * hugepage PTEs.  We could optimize this in the future
+		 * use page_cache_add_speculative() for the hugepage case.
+		 */
+		page = pte_page(pte);
+		head = compound_head(page);
+		if (!page_cache_get_speculative(head))
+			return 0;
+		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
+			put_page(head);
+			return 0;
+		}
+
+		pages[*nr] = page;
+		(*nr)++;
+	} while (ptep++, addr += PAGE_SIZE, addr != end);
+
+	return 1;
+}
+
+static int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
+			unsigned long end, int write, struct page **pages,
+			int *nr)
+{
+	struct page *head, *page;
+	int refs;
+
+	if (!(pmd_val(pmd) & _PAGE_VALID))
+		return 0;
+
+	if (write && !pmd_write(pmd))
+		return 0;
+
+	refs = 0;
+	page = pmd_page(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+	head = compound_head(page);
+	do {
+		VM_BUG_ON(compound_head(page) != head);
+		pages[*nr] = page;
+		(*nr)++;
+		page++;
+		refs++;
+	} while (addr += PAGE_SIZE, addr != end);
+
+	if (!page_cache_add_speculative(head, refs)) {
+		*nr -= refs;
+		return 0;
+	}
+
+	if (unlikely(pmd_val(pmd) != pmd_val(*pmdp))) {
+		*nr -= refs;
+		while (refs--)
+			put_page(head);
+		return 0;
+	}
+
+	return 1;
+}
+
+static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr,
+			unsigned long end, int write, struct page **pages,
+			int *nr)
+{
+	struct page *head, *page;
+	int refs;
+
+	if (!(pud_val(pud) & _PAGE_VALID))
+		return 0;
+
+	if (write && !pud_write(pud))
+		return 0;
+
+	refs = 0;
+	page = pud_page(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
+	head = compound_head(page);
+	do {
+		VM_BUG_ON(compound_head(page) != head);
+		pages[*nr] = page;
+		(*nr)++;
+		page++;
+		refs++;
+	} while (addr += PAGE_SIZE, addr != end);
+
+	if (!page_cache_add_speculative(head, refs)) {
+		*nr -= refs;
+		return 0;
+	}
+
+	if (unlikely(pud_val(pud) != pud_val(*pudp))) {
+		*nr -= refs;
+		while (refs--)
+			put_page(head);
+		return 0;
+	}
+
+	return 1;
+}
+
+static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
+		int write, struct page **pages, int *nr)
+{
+	unsigned long next;
+	pmd_t *pmdp;
+
+	pmdp = pmd_offset(&pud, addr);
+	do {
+		pmd_t pmd = *pmdp;
+
+		next = pmd_addr_end(addr, end);
+		if (pmd_none(pmd))
+			return 0;
+		if (unlikely(pmd_large(pmd))) {
+			if (!gup_huge_pmd(pmdp, pmd, addr, next,
+					  write, pages, nr))
+				return 0;
+		} else if (!gup_pte_range(pmd, addr, next, write,
+					  pages, nr))
+			return 0;
+	} while (pmdp++, addr = next, addr != end);
+
+	return 1;
+}
+
+static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
+		int write, struct page **pages, int *nr)
+{
+	unsigned long next;
+	pud_t *pudp;
+
+	pudp = pud_offset(&pgd, addr);
+	do {
+		pud_t pud = *pudp;
+
+		next = pud_addr_end(addr, end);
+		if (pud_none(pud))
+			return 0;
+		if (unlikely(pud_large(pud))) {
+			if (!gup_huge_pud(pudp, pud, addr, next,
+					  write, pages, nr))
+				return 0;
+		} else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
+			return 0;
+	} while (pudp++, addr = next, addr != end);
+
+	return 1;
+}
+
+/*
+ * Note a difference with get_user_pages_fast: this always returns the
+ * number of pages pinned, 0 if no pages were pinned.
+ */
+int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
+			  struct page **pages)
+{
+	struct mm_struct *mm = current->mm;
+	unsigned long addr, len, end;
+	unsigned long next, flags;
+	pgd_t *pgdp;
+	int nr = 0;
+
+#ifdef CONFIG_SPARC64
+	if (adi_capable()) {
+		long addr = start;
+
+		/* If userspace has passed a versioned address, kernel
+		 * will not find it in the VMAs since it does not store
+		 * the version tags in the list of VMAs. Storing version
+		 * tags in list of VMAs is impractical since they can be
+		 * changed any time from userspace without dropping into
+		 * kernel. Any address search in VMAs will be done with
+		 * non-versioned addresses. Ensure the ADI version bits
+		 * are dropped here by sign extending the last bit before
+		 * ADI bits. IOMMU does not implement version tags.
+		 */
+		addr = (addr << (long)adi_nbits()) >> (long)adi_nbits();
+		start = addr;
+	}
+#endif
+	start &= PAGE_MASK;
+	addr = start;
+	len = (unsigned long) nr_pages << PAGE_SHIFT;
+	end = start + len;
+
+	local_irq_save(flags);
+	pgdp = pgd_offset(mm, addr);
+	do {
+		pgd_t pgd = *pgdp;
+
+		next = pgd_addr_end(addr, end);
+		if (pgd_none(pgd))
+			break;
+		if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
+			break;
+	} while (pgdp++, addr = next, addr != end);
+	local_irq_restore(flags);
+
+	return nr;
+}
+
+int get_user_pages_fast(unsigned long start, int nr_pages, int write,
+			struct page **pages)
+{
+	struct mm_struct *mm = current->mm;
+	unsigned long addr, len, end;
+	unsigned long next;
+	pgd_t *pgdp;
+	int nr = 0;
+
+#ifdef CONFIG_SPARC64
+	if (adi_capable()) {
+		long addr = start;
+
+		/* If userspace has passed a versioned address, kernel
+		 * will not find it in the VMAs since it does not store
+		 * the version tags in the list of VMAs. Storing version
+		 * tags in list of VMAs is impractical since they can be
+		 * changed any time from userspace without dropping into
+		 * kernel. Any address search in VMAs will be done with
+		 * non-versioned addresses. Ensure the ADI version bits
+		 * are dropped here by sign extending the last bit before
+		 * ADI bits. IOMMU does not implements version tags,
+		 */
+		addr = (addr << (long)adi_nbits()) >> (long)adi_nbits();
+		start = addr;
+	}
+#endif
+	start &= PAGE_MASK;
+	addr = start;
+	len = (unsigned long) nr_pages << PAGE_SHIFT;
+	end = start + len;
+
+	/*
+	 * XXX: batch / limit 'nr', to avoid large irq off latency
+	 * needs some instrumenting to determine the common sizes used by
+	 * important workloads (eg. DB2), and whether limiting the batch size
+	 * will decrease performance.
+	 *
+	 * It seems like we're in the clear for the moment. Direct-IO is
+	 * the main guy that batches up lots of get_user_pages, and even
+	 * they are limited to 64-at-a-time which is not so many.
+	 */
+	/*
+	 * This doesn't prevent pagetable teardown, but does prevent
+	 * the pagetables from being freed on sparc.
+	 *
+	 * So long as we atomically load page table pointers versus teardown,
+	 * we can follow the address down to the the page and take a ref on it.
+	 */
+	local_irq_disable();
+
+	pgdp = pgd_offset(mm, addr);
+	do {
+		pgd_t pgd = *pgdp;
+
+		next = pgd_addr_end(addr, end);
+		if (pgd_none(pgd))
+			goto slow;
+		/*
+		 * The FAST_GUP case requires FOLL_WRITE even for pure reads,
+		 * because get_user_pages() may need to cause an early COW in
+		 * order to avoid confusing the normal COW routines. So only
+		 * targets that are already writable are safe to do by just
+		 * looking at the page tables.
+		 */
+		if (!gup_pud_range(pgd, addr, next, 1, pages, &nr))
+			goto slow;
+	} while (pgdp++, addr = next, addr != end);
+
+	local_irq_enable();
+
+	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
+	return nr;
+
+	{
+		int ret;
+
+slow:
+		local_irq_enable();
+
+		/* Try to get the remaining pages with get_user_pages */
+		start += nr << PAGE_SHIFT;
+		pages += nr;
+
+		ret = get_user_pages_unlocked(start,
+			(end - start) >> PAGE_SHIFT, pages,
+			write ? FOLL_WRITE : 0);
+
+		/* Have to be a bit careful with return values */
+		if (nr > 0) {
+			if (ret < 0)
+				ret = nr;
+			else
+				ret += nr;
+		}
+
+		return ret;
+	}
+}