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From: Christoph Hellwig <hch@lst.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Juergen Gross <jgross@suse.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
	Chris Wilson <chris@chris-wilson.co.uk>,
	Matthew Auld <matthew.auld@intel.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Minchan Kim <minchan@kernel.org>,
	Matthew Wilcox <willy@infradead.org>,
	Nitin Gupta <ngupta@vflare.org>,
	x86@kernel.org, xen-devel@lists.xenproject.org,
	linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org,
	dri-devel@lists.freedesktop.org, linux-mm@kvack.org
Subject: [PATCH 03/10] mm: add a vmap_pfn function
Date: Wed, 30 Sep 2020 19:51:26 +0200
Message-ID: <20200930175133.1252382-4-hch@lst.de> (raw)
In-Reply-To: <20200930175133.1252382-1-hch@lst.de>

Add a proper helper to remap PFNs into kernel virtual space so that
drivers don't have to abuse alloc_vm_area and open coded PTE
manipulation for it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/vmalloc.h |  1 +
 mm/Kconfig              |  3 +++
 mm/vmalloc.c            | 45 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index b899681e3ff9f0..c77efeac242514 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -122,6 +122,7 @@ extern void vfree_atomic(const void *addr);
 
 extern void *vmap(struct page **pages, unsigned int count,
 			unsigned long flags, pgprot_t prot);
+void *vmap_pfn(unsigned long *pfns, unsigned int count, pgprot_t prot);
 extern void vunmap(const void *addr);
 
 extern int remap_vmalloc_range_partial(struct vm_area_struct *vma,
diff --git a/mm/Kconfig b/mm/Kconfig
index 6c974888f86f97..6fa7ba1199eb1e 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -815,6 +815,9 @@ config DEVICE_PRIVATE
 	  memory; i.e., memory that is only accessible from the device (or
 	  group of devices). You likely also want to select HMM_MIRROR.
 
+config VMAP_PFN
+	bool
+
 config FRAME_VECTOR
 	bool
 
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index ffad65f052c3f9..e2a2ded8d93478 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2413,6 +2413,51 @@ void *vmap(struct page **pages, unsigned int count,
 }
 EXPORT_SYMBOL(vmap);
 
+#ifdef CONFIG_VMAP_PFN
+struct vmap_pfn_data {
+	unsigned long	*pfns;
+	pgprot_t	prot;
+	unsigned int	idx;
+};
+
+static int vmap_pfn_apply(pte_t *pte, unsigned long addr, void *private)
+{
+	struct vmap_pfn_data *data = private;
+
+	if (WARN_ON_ONCE(pfn_valid(data->pfns[data->idx])))
+		return -EINVAL;
+	*pte = pte_mkspecial(pfn_pte(data->pfns[data->idx++], data->prot));
+	return 0;
+}
+
+/**
+ * vmap_pfn - map an array of PFNs into virtually contiguous space
+ * @pfns: array of PFNs
+ * @count: number of pages to map
+ * @prot: page protection for the mapping
+ *
+ * Maps @count PFNs from @pfns into contiguous kernel virtual space and returns
+ * the start address of the mapping.
+ */
+void *vmap_pfn(unsigned long *pfns, unsigned int count, pgprot_t prot)
+{
+	struct vmap_pfn_data data = { .pfns = pfns, .prot = pgprot_nx(prot) };
+	struct vm_struct *area;
+
+	area = get_vm_area_caller(count * PAGE_SIZE, VM_IOREMAP,
+			__builtin_return_address(0));
+	if (!area)
+		return NULL;
+	if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
+			count * PAGE_SIZE, vmap_pfn_apply, &data)) {
+		free_vm_area(area);
+		return NULL;
+	}
+	return area->addr;
+}
+EXPORT_SYMBOL_GPL(vmap_pfn);
+#endif /* CONFIG_VMAP_PFN */
+
 static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 				 pgprot_t prot, int node)
 {
-- 
2.28.0


  parent reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-30 17:51 remove alloc_vm_area v3 Christoph Hellwig
2020-09-30 17:51 ` [PATCH 01/10] mm: update the documentation for vfree Christoph Hellwig
2020-09-30 17:51 ` [PATCH 02/10] mm: add a VM_MAP_PUT_PAGES flag for vmap Christoph Hellwig
2020-09-30 17:51 ` Christoph Hellwig [this message]
2020-09-30 17:51 ` [PATCH 04/10] mm: allow a NULL fn callback in apply_to_page_range Christoph Hellwig
2020-09-30 17:51 ` [PATCH 05/10] zsmalloc: switch from alloc_vm_area to get_vm_area Christoph Hellwig
2020-09-30 17:51 ` [PATCH 06/10] drm/i915: use vmap in shmem_pin_map Christoph Hellwig
2020-09-30 17:51 ` [PATCH 07/10] drm/i915: use vmap in i915_gem_object_map Christoph Hellwig
2020-09-30 17:51 ` [PATCH 08/10] xen/xenbus: use apply_to_page_range directly in xenbus_map_ring_pv Christoph Hellwig
2020-09-30 17:51 ` [PATCH 09/10] x86/xen: open code alloc_vm_area in arch_gnttab_valloc Christoph Hellwig
2020-09-30 17:51 ` [PATCH 10/10] mm: remove alloc_vm_area Christoph Hellwig

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