Add a new type of VM object: OBJT_SG. An OBJT_SG object is very similar to

a device pager (OBJT_DEVICE) object in that it uses fictitious pages to
provide aliases to other memory addresses.  The primary difference is that
it uses an sglist(9) to determine the physical addresses for a given offset
into the object instead of invoking the d_mmap() method in a device driver.

Reviewed by:	alc
Approved by:	re (kensmith)
MFC after:	2 weeks

1 files changed, 263 insertions, 0 deletions

diff --git a/sys/vm/sg_pager.c b/sys/vm/sg_pager.c
new file mode 100644
index 0000000..bf3390f
--- /dev/null
+++ b/sys/vm/sg_pager.c
@@ -0,0 +1,263 @@
+/*-
+ * Copyright (c) 2009 Advanced Computing Technologies LLC
+ * Written by: John H. Baldwin <jhb@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+/*
+ * This pager manages OBJT_SG objects.  These objects are backed by
+ * a scatter/gather list of physical address ranges.
+ */
+
+#include <sys/param.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
+#include <sys/sglist.h>
+#include <vm/vm.h>
+#include <vm/vm_object.h>
+#include <vm/vm_page.h>
+#include <vm/vm_pager.h>
+#include <vm/uma.h>
+
+static void sg_pager_init(void);
+static vm_object_t sg_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
+    vm_ooffset_t, struct ucred *);
+static void sg_pager_dealloc(vm_object_t);
+static int sg_pager_getpages(vm_object_t, vm_page_t *, int, int);
+static void sg_pager_putpages(vm_object_t, vm_page_t *, int, 
+		boolean_t, int *);
+static boolean_t sg_pager_haspage(vm_object_t, vm_pindex_t, int *,
+		int *);
+
+static uma_zone_t fakepg_zone;
+
+static vm_page_t sg_pager_getfake(vm_paddr_t, vm_memattr_t);
+static void sg_pager_putfake(vm_page_t);
+
+struct pagerops sgpagerops = {
+	.pgo_init =	sg_pager_init,
+	.pgo_alloc =	sg_pager_alloc,
+	.pgo_dealloc =	sg_pager_dealloc,
+	.pgo_getpages =	sg_pager_getpages,
+	.pgo_putpages =	sg_pager_putpages,
+	.pgo_haspage =	sg_pager_haspage,
+};
+
+static void
+sg_pager_init(void)
+{
+
+	fakepg_zone = uma_zcreate("SG fakepg", sizeof(struct vm_page),
+	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR,
+	    UMA_ZONE_NOFREE|UMA_ZONE_VM); 
+}
+
+static vm_object_t
+sg_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
+    vm_ooffset_t foff, struct ucred *cred)
+{
+	struct sglist *sg;
+	vm_object_t object;
+	vm_pindex_t npages, pindex;
+	int i;
+
+	/*
+	 * Offset should be page aligned.
+	 */
+	if (foff & PAGE_MASK)
+		return (NULL);
+
+	/*
+	 * The scatter/gather list must only include page-aligned
+	 * ranges.
+	 */
+	npages = 0;
+	sg = handle;
+	for (i = 0; i < sg->sg_nseg; i++) {
+		if ((sg->sg_segs[i].ss_paddr % PAGE_SIZE) != 0 ||
+		    (sg->sg_segs[i].ss_len % PAGE_SIZE) != 0)
+			return (NULL);
+		npages += sg->sg_segs[i].ss_len / PAGE_SIZE;
+	}
+
+	/*
+	 * The scatter/gather list has a fixed size.  Refuse requests
+	 * to map beyond that.
+	 */
+	size = round_page(size);
+	pindex = OFF_TO_IDX(foff + size);
+	if (pindex > npages)
+		return (NULL);
+
+	/*
+	 * Allocate a new object and associate it with the
+	 * scatter/gather list.  It is ok for our purposes to have
+	 * multiple VM objects associated with the same scatter/gather
+	 * list because scatter/gather lists are static.  This is also
+	 * simpler than ensuring a unique object per scatter/gather
+	 * list.
+	 */
+	object = vm_object_allocate(OBJT_SG, npages);
+	object->handle = sglist_hold(sg);
+	TAILQ_INIT(&object->un_pager.sgp.sgp_pglist);
+	return (object);
+}
+
+static void
+sg_pager_dealloc(vm_object_t object)
+{
+	struct sglist *sg;
+	vm_page_t m;
+
+	/*
+	 * Free up our fake pages.
+	 */
+	while ((m = TAILQ_FIRST(&object->un_pager.sgp.sgp_pglist)) != 0) {
+		TAILQ_REMOVE(&object->un_pager.sgp.sgp_pglist, m, pageq);
+		sg_pager_putfake(m);
+	}
+	
+	sg = object->handle;
+	sglist_free(sg);
+}
+
+static int
+sg_pager_getpages(vm_object_t object, vm_page_t *m, int count, int reqpage)
+{
+	struct sglist *sg;
+	vm_page_t m_paddr, page;
+	vm_pindex_t offset;
+	vm_paddr_t paddr;
+	vm_memattr_t memattr;
+	size_t space;
+	int i;
+
+	VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
+	sg = object->handle;
+	memattr = object->memattr;
+	VM_OBJECT_UNLOCK(object);
+	offset = m[reqpage]->pindex;
+
+	/*
+	 * Lookup the physical address of the requested page.  An initial
+	 * value of '1' instead of '0' is used so we can assert that the
+	 * page is found since '0' can be a valid page-aligned physical
+	 * address.
+	 */
+	space = 0;
+	paddr = 1;
+	for (i = 0; i < sg->sg_nseg; i++) {
+		if (space + sg->sg_segs[i].ss_len <= (offset * PAGE_SIZE)) {
+			space += sg->sg_segs[i].ss_len;
+			continue;
+		}
+		paddr = sg->sg_segs[i].ss_paddr + offset * PAGE_SIZE - space;
+		break;
+	}
+	KASSERT(paddr != 1, ("invalid SG page index"));
+
+	/* If "paddr" is a real page, perform a sanity check on "memattr". */
+	if ((m_paddr = vm_phys_paddr_to_vm_page(paddr)) != NULL &&
+	    pmap_page_get_memattr(m_paddr) != memattr) {
+		memattr = pmap_page_get_memattr(m_paddr);
+		printf(
+	    "WARNING: A device driver has set \"memattr\" inconsistently.\n");
+	}
+
+	/* Return a fake page for the requested page. */
+	KASSERT(!(m[reqpage]->flags & PG_FICTITIOUS),
+	    ("backing page for SG is fake"));
+
+	/* Construct a new fake page. */
+	printf("SG: getting fake page for paddr %lx\n", paddr);
+	page = sg_pager_getfake(paddr, memattr);
+	VM_OBJECT_LOCK(object);
+	TAILQ_INSERT_TAIL(&object->un_pager.sgp.sgp_pglist, page, pageq);
+
+	/* Free the original pages and insert this fake page into the object. */
+	vm_page_lock_queues();
+	for (i = 0; i < count; i++) {
+		printf("SG: freeing VM page %p\n", m[i]);
+		vm_page_free(m[i]);
+	}
+	vm_page_unlock_queues();
+	printf("SG: Inserting new fake page\n");
+	vm_page_insert(page, object, offset);
+	m[reqpage] = page;
+
+	return (VM_PAGER_OK);
+}
+
+static void
+sg_pager_putpages(vm_object_t object, vm_page_t *m, int count,
+    boolean_t sync, int *rtvals)
+{
+
+	panic("sg_pager_putpage called");
+}
+
+static boolean_t
+sg_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
+    int *after)
+{
+
+	if (before != NULL)
+		*before = 0;
+	if (after != NULL)
+		*after = 0;
+	return (TRUE);
+}
+
+/*
+ * Create a fictitious page with the specified physical address and memory
+ * attribute.  The memory attribute is the only the machine-dependent aspect
+ * of a fictitious page that must be initialized.
+ */
+static vm_page_t
+sg_pager_getfake(vm_paddr_t paddr, vm_memattr_t memattr)
+{
+	vm_page_t m;
+
+	m = uma_zalloc(fakepg_zone, M_WAITOK | M_ZERO);
+	m->phys_addr = paddr;
+	/* Fictitious pages don't use "segind". */
+	m->flags = PG_FICTITIOUS;
+	/* Fictitious pages don't use "order" or "pool". */
+	m->oflags = VPO_BUSY;
+	m->wire_count = 1;
+	pmap_page_set_memattr(m, memattr);
+	return (m);
+}
+
+static void
+sg_pager_putfake(vm_page_t m)
+{
+
+	if (!(m->flags & PG_FICTITIOUS))
+		panic("sg_pager_putfake: bad page");
+	uma_zfree(fakepg_zone, m);
+}