Merge tag 'for-linus-5.15-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from Juergen Gross:

 - some small cleanups

 - a fix for a bug when running as Xen PV guest which could result in
   not all memory being transferred in case of a migration of the guest

 - a small series for getting rid of code for supporting very old Xen
   hypervisor versions nobody should be using since many years now

 - a series for hardening the Xen block frontend driver

 - a fix for Xen PV boot code issuing warning messages due to a stray
   preempt_disable() on the non-boot processors

* tag 'for-linus-5.15-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen: remove stray preempt_disable() from PV AP startup code
  xen/pcifront: Removed unnecessary __ref annotation
  x86: xen: platform-pci-unplug: use pr_err() and pr_warn() instead of raw printk()
  drivers/xen/xenbus/xenbus_client.c: fix bugon.cocci warnings
  xen/blkfront: don't trust the backend response data blindly
  xen/blkfront: don't take local copy of a request from the ring page
  xen/blkfront: read response from backend only once
  xen: assume XENFEAT_gnttab_map_avail_bits being set for pv guests
  xen: assume XENFEAT_mmu_pt_update_preserve_ad being set for pv guests
  xen: check required Xen features
  xen: fix setting of max_pfn in shared_info

arch/x86/xen/enlighten_pv.c

@@ -116,9 +116,8 @@ static void __init xen_banner(void)
 	HYPERVISOR_xen_version(XENVER_extraversion, &extra);
 
 	pr_info("Booting paravirtualized kernel on %s\n", pv_info.name);
-	printk(KERN_INFO "Xen version: %d.%d%s%s\n",
-	       version >> 16, version & 0xffff, extra.extraversion,
-	       xen_feature(XENFEAT_mmu_pt_update_preserve_ad) ? " (preserve-AD)" : "");
+	pr_info("Xen version: %d.%d%s (preserve-AD)\n",
+		version >> 16, version & 0xffff, extra.extraversion);
 }
 
 static void __init xen_pv_init_platform(void)
@@ -1302,13 +1301,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
 	xen_init_apic();
 #endif
 
-	if (xen_feature(XENFEAT_mmu_pt_update_preserve_ad)) {
-		pv_ops.mmu.ptep_modify_prot_start =
-			xen_ptep_modify_prot_start;
-		pv_ops.mmu.ptep_modify_prot_commit =
-			xen_ptep_modify_prot_commit;
-	}
-
 	machine_ops = xen_machine_ops;
 
 	/*

arch/x86/xen/mmu_pv.c

@@ -2099,8 +2099,8 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = {
 	.set_pte = xen_set_pte_init,
 	.set_pmd = xen_set_pmd_hyper,
 
-	.ptep_modify_prot_start = __ptep_modify_prot_start,
-	.ptep_modify_prot_commit = __ptep_modify_prot_commit,
+	.ptep_modify_prot_start = xen_ptep_modify_prot_start,
+	.ptep_modify_prot_commit = xen_ptep_modify_prot_commit,
 
 	.pte_val = PV_CALLEE_SAVE(xen_pte_val),
 	.pgd_val = PV_CALLEE_SAVE(xen_pgd_val),

arch/x86/xen/p2m.c

@@ -618,8 +618,8 @@ int xen_alloc_p2m_entry(unsigned long pfn)
 	}
 
 	/* Expanded the p2m? */
-	if (pfn > xen_p2m_last_pfn) {
-		xen_p2m_last_pfn = pfn;
+	if (pfn >= xen_p2m_last_pfn) {
+		xen_p2m_last_pfn = ALIGN(pfn + 1, P2M_PER_PAGE);
 		HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
 	}
 

arch/x86/xen/platform-pci-unplug.c

@@ -7,6 +7,8 @@
  * Copyright (c) 2010, Citrix
  */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/init.h>
 #include <linux/io.h>
 #include <linux/export.h>
@@ -30,13 +32,13 @@ static int check_platform_magic(void)
 
 	magic = inw(XEN_IOPORT_MAGIC);
 	if (magic != XEN_IOPORT_MAGIC_VAL) {
-		printk(KERN_ERR "Xen Platform PCI: unrecognised magic value\n");
+		pr_err("Xen Platform PCI: unrecognised magic value\n");
 		return XEN_PLATFORM_ERR_MAGIC;
 	}
 
 	protocol = inb(XEN_IOPORT_PROTOVER);
 
-	printk(KERN_DEBUG "Xen Platform PCI: I/O protocol version %d\n",
+	pr_debug("Xen Platform PCI: I/O protocol version %d\n",
 			protocol);
 
 	switch (protocol) {
@@ -44,12 +46,12 @@ static int check_platform_magic(void)
 		outw(XEN_IOPORT_LINUX_PRODNUM, XEN_IOPORT_PRODNUM);
 		outl(XEN_IOPORT_LINUX_DRVVER, XEN_IOPORT_DRVVER);
 		if (inw(XEN_IOPORT_MAGIC) != XEN_IOPORT_MAGIC_VAL) {
-			printk(KERN_ERR "Xen Platform: blacklisted by host\n");
+			pr_err("Xen Platform: blacklisted by host\n");
 			return XEN_PLATFORM_ERR_BLACKLIST;
 		}
 		break;
 	default:
-		printk(KERN_WARNING "Xen Platform PCI: unknown I/O protocol version\n");
+		pr_warn("Xen Platform PCI: unknown I/O protocol version\n");
 		return XEN_PLATFORM_ERR_PROTOCOL;
 	}
 
@@ -155,12 +157,12 @@ void xen_unplug_emulated_devices(void)
 	 * been compiled for this kernel (modules or built-in are both OK). */
 	if (!xen_emul_unplug) {
 		if (xen_must_unplug_nics()) {
-			printk(KERN_INFO "Netfront and the Xen platform PCI driver have "
+			pr_info("Netfront and the Xen platform PCI driver have "
 					"been compiled for this kernel: unplug emulated NICs.\n");
 			xen_emul_unplug |= XEN_UNPLUG_ALL_NICS;
 		}
 		if (xen_must_unplug_disks()) {
-			printk(KERN_INFO "Blkfront and the Xen platform PCI driver have "
+			pr_info("Blkfront and the Xen platform PCI driver have "
 					"been compiled for this kernel: unplug emulated disks.\n"
 					"You might have to change the root device\n"
 					"from /dev/hd[a-d] to /dev/xvd[a-d]\n"
@@ -200,7 +202,7 @@ static int __init parse_xen_emul_unplug(char *arg)
 		else if (!strncmp(p, "never", l))
 			xen_emul_unplug |= XEN_UNPLUG_NEVER;
 		else
-			printk(KERN_WARNING "unrecognised option '%s' "
+			pr_warn("unrecognised option '%s' "
 				 "in parameter 'xen_emul_unplug'\n", p);
 	}
 	return 0;

arch/x86/xen/smp_pv.c

@@ -64,7 +64,6 @@ static void cpu_bringup(void)
 	cr4_init();
 	cpu_init();
 	touch_softlockup_watchdog();
-	preempt_disable();
 
 	/* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
 	if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {

drivers/block/xen-blkfront.c

@@ -80,6 +80,7 @@ enum blkif_state {
 	BLKIF_STATE_DISCONNECTED,
 	BLKIF_STATE_CONNECTED,
 	BLKIF_STATE_SUSPENDED,
+	BLKIF_STATE_ERROR,
 };
 
 struct grant {
@@ -89,6 +90,7 @@ struct grant {
 };
 
 enum blk_req_status {
+	REQ_PROCESSING,
 	REQ_WAITING,
 	REQ_DONE,
 	REQ_ERROR,
@@ -530,10 +532,10 @@ static unsigned long blkif_ring_get_request(struct blkfront_ring_info *rinfo,
 
 	id = get_id_from_freelist(rinfo);
 	rinfo->shadow[id].request = req;
-	rinfo->shadow[id].status = REQ_WAITING;
+	rinfo->shadow[id].status = REQ_PROCESSING;
 	rinfo->shadow[id].associated_id = NO_ASSOCIATED_ID;
 
-	(*ring_req)->u.rw.id = id;
+	rinfo->shadow[id].req.u.rw.id = id;
 
 	return id;
 }
@@ -541,11 +543,12 @@ static unsigned long blkif_ring_get_request(struct blkfront_ring_info *rinfo,
 static int blkif_queue_discard_req(struct request *req, struct blkfront_ring_info *rinfo)
 {
 	struct blkfront_info *info = rinfo->dev_info;
-	struct blkif_request *ring_req;
+	struct blkif_request *ring_req, *final_ring_req;
 	unsigned long id;
 
 	/* Fill out a communications ring structure. */
-	id = blkif_ring_get_request(rinfo, req, &ring_req);
+	id = blkif_ring_get_request(rinfo, req, &final_ring_req);
+	ring_req = &rinfo->shadow[id].req;
 
 	ring_req->operation = BLKIF_OP_DISCARD;
 	ring_req->u.discard.nr_sectors = blk_rq_sectors(req);
@@ -556,8 +559,9 @@ static int blkif_queue_discard_req(struct request *req, struct blkfront_ring_inf
 	else
 		ring_req->u.discard.flag = 0;
 
-	/* Keep a private copy so we can reissue requests when recovering. */
-	rinfo->shadow[id].req = *ring_req;
+	/* Copy the request to the ring page. */
+	*final_ring_req = *ring_req;
+	rinfo->shadow[id].status = REQ_WAITING;
 
 	return 0;
 }
@@ -690,6 +694,7 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
 {
 	struct blkfront_info *info = rinfo->dev_info;
 	struct blkif_request *ring_req, *extra_ring_req = NULL;
+	struct blkif_request *final_ring_req, *final_extra_ring_req = NULL;
 	unsigned long id, extra_id = NO_ASSOCIATED_ID;
 	bool require_extra_req = false;
 	int i;
@@ -734,7 +739,8 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
 	}
 
 	/* Fill out a communications ring structure. */
-	id = blkif_ring_get_request(rinfo, req, &ring_req);
+	id = blkif_ring_get_request(rinfo, req, &final_ring_req);
+	ring_req = &rinfo->shadow[id].req;
 
 	num_sg = blk_rq_map_sg(req->q, req, rinfo->shadow[id].sg);
 	num_grant = 0;
@@ -785,7 +791,9 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
 		ring_req->u.rw.nr_segments = num_grant;
 		if (unlikely(require_extra_req)) {
 			extra_id = blkif_ring_get_request(rinfo, req,
-							  &extra_ring_req);
+							  &final_extra_ring_req);
+			extra_ring_req = &rinfo->shadow[extra_id].req;
+
 			/*
 			 * Only the first request contains the scatter-gather
 			 * list.
@@ -827,10 +835,13 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
 	if (setup.segments)
 		kunmap_atomic(setup.segments);
 
-	/* Keep a private copy so we can reissue requests when recovering. */
-	rinfo->shadow[id].req = *ring_req;
-	if (unlikely(require_extra_req))
-		rinfo->shadow[extra_id].req = *extra_ring_req;
+	/* Copy request(s) to the ring page. */
+	*final_ring_req = *ring_req;
+	rinfo->shadow[id].status = REQ_WAITING;
+	if (unlikely(require_extra_req)) {
+		*final_extra_ring_req = *extra_ring_req;
+		rinfo->shadow[extra_id].status = REQ_WAITING;
+	}
 
 	if (new_persistent_gnts)
 		gnttab_free_grant_references(setup.gref_head);
@@ -1353,8 +1364,8 @@ static enum blk_req_status blkif_rsp_to_req_status(int rsp)
 static int blkif_get_final_status(enum blk_req_status s1,
 				  enum blk_req_status s2)
 {
-	BUG_ON(s1 == REQ_WAITING);
-	BUG_ON(s2 == REQ_WAITING);
+	BUG_ON(s1 < REQ_DONE);
+	BUG_ON(s2 < REQ_DONE);
 
 	if (s1 == REQ_ERROR || s2 == REQ_ERROR)
 		return BLKIF_RSP_ERROR;
@@ -1387,7 +1398,7 @@ static bool blkif_completion(unsigned long *id,
 		s->status = blkif_rsp_to_req_status(bret->status);
 
 		/* Wait the second response if not yet here. */
-		if (s2->status == REQ_WAITING)
+		if (s2->status < REQ_DONE)
 			return false;
 
 		bret->status = blkif_get_final_status(s->status,
@@ -1495,7 +1506,7 @@ static bool blkif_completion(unsigned long *id,
 static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 {
 	struct request *req;
-	struct blkif_response *bret;
+	struct blkif_response bret;
 	RING_IDX i, rp;
 	unsigned long flags;
 	struct blkfront_ring_info *rinfo = (struct blkfront_ring_info *)dev_id;
@@ -1506,54 +1517,76 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 
 	spin_lock_irqsave(&rinfo->ring_lock, flags);
  again:
-	rp = rinfo->ring.sring->rsp_prod;
-	rmb(); /* Ensure we see queued responses up to 'rp'. */
+	rp = READ_ONCE(rinfo->ring.sring->rsp_prod);
+	virt_rmb(); /* Ensure we see queued responses up to 'rp'. */
+	if (RING_RESPONSE_PROD_OVERFLOW(&rinfo->ring, rp)) {
+		pr_alert("%s: illegal number of responses %u\n",
+			 info->gd->disk_name, rp - rinfo->ring.rsp_cons);
+		goto err;
+	}
 
 	for (i = rinfo->ring.rsp_cons; i != rp; i++) {
 		unsigned long id;
+		unsigned int op;
+
+		RING_COPY_RESPONSE(&rinfo->ring, i, &bret);
+		id = bret.id;
 
-		bret = RING_GET_RESPONSE(&rinfo->ring, i);
-		id   = bret->id;
 		/*
 		 * The backend has messed up and given us an id that we would
 		 * never have given to it (we stamp it up to BLK_RING_SIZE -
 		 * look in get_id_from_freelist.
 		 */
 		if (id >= BLK_RING_SIZE(info)) {
-			WARN(1, "%s: response to %s has incorrect id (%ld)\n",
-			     info->gd->disk_name, op_name(bret->operation), id);
-			/* We can't safely get the 'struct request' as
-			 * the id is busted. */
-			continue;
+			pr_alert("%s: response has incorrect id (%ld)\n",
+				 info->gd->disk_name, id);
+			goto err;
 		}
+		if (rinfo->shadow[id].status != REQ_WAITING) {
+			pr_alert("%s: response references no pending request\n",
+				 info->gd->disk_name);
+			goto err;
+		}
+
+		rinfo->shadow[id].status = REQ_PROCESSING;
 		req  = rinfo->shadow[id].request;
 
-		if (bret->operation != BLKIF_OP_DISCARD) {
+		op = rinfo->shadow[id].req.operation;
+		if (op == BLKIF_OP_INDIRECT)
+			op = rinfo->shadow[id].req.u.indirect.indirect_op;
+		if (bret.operation != op) {
+			pr_alert("%s: response has wrong operation (%u instead of %u)\n",
+				 info->gd->disk_name, bret.operation, op);
+			goto err;
+		}
+
+		if (bret.operation != BLKIF_OP_DISCARD) {
 			/*
 			 * We may need to wait for an extra response if the
 			 * I/O request is split in 2
 			 */
-			if (!blkif_completion(&id, rinfo, bret))
+			if (!blkif_completion(&id, rinfo, &bret))
 				continue;
 		}
 
 		if (add_id_to_freelist(rinfo, id)) {
 			WARN(1, "%s: response to %s (id %ld) couldn't be recycled!\n",
-			     info->gd->disk_name, op_name(bret->operation), id);
+			     info->gd->disk_name, op_name(bret.operation), id);
 			continue;
 		}
 
-		if (bret->status == BLKIF_RSP_OKAY)
+		if (bret.status == BLKIF_RSP_OKAY)
 			blkif_req(req)->error = BLK_STS_OK;
 		else
 			blkif_req(req)->error = BLK_STS_IOERR;
 
-		switch (bret->operation) {
+		switch (bret.operation) {
 		case BLKIF_OP_DISCARD:
-			if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
+			if (unlikely(bret.status == BLKIF_RSP_EOPNOTSUPP)) {
 				struct request_queue *rq = info->rq;
-				printk(KERN_WARNING "blkfront: %s: %s op failed\n",
-					   info->gd->disk_name, op_name(bret->operation));
+
+				pr_warn_ratelimited("blkfront: %s: %s op failed\n",
+					   info->gd->disk_name, op_name(bret.operation));
 				blkif_req(req)->error = BLK_STS_NOTSUPP;
 				info->feature_discard = 0;
 				info->feature_secdiscard = 0;
@@ -1563,15 +1596,15 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 			break;
 		case BLKIF_OP_FLUSH_DISKCACHE:
 		case BLKIF_OP_WRITE_BARRIER:
-			if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
-				printk(KERN_WARNING "blkfront: %s: %s op failed\n",
-				       info->gd->disk_name, op_name(bret->operation));
+			if (unlikely(bret.status == BLKIF_RSP_EOPNOTSUPP)) {
+				pr_warn_ratelimited("blkfront: %s: %s op failed\n",
+				       info->gd->disk_name, op_name(bret.operation));
 				blkif_req(req)->error = BLK_STS_NOTSUPP;
 			}
-			if (unlikely(bret->status == BLKIF_RSP_ERROR &&
+			if (unlikely(bret.status == BLKIF_RSP_ERROR &&
 				     rinfo->shadow[id].req.u.rw.nr_segments == 0)) {
-				printk(KERN_WARNING "blkfront: %s: empty %s op failed\n",
-				       info->gd->disk_name, op_name(bret->operation));
+				pr_warn_ratelimited("blkfront: %s: empty %s op failed\n",
+				       info->gd->disk_name, op_name(bret.operation));
 				blkif_req(req)->error = BLK_STS_NOTSUPP;
 			}
 			if (unlikely(blkif_req(req)->error)) {
@@ -1584,9 +1617,10 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 			fallthrough;
 		case BLKIF_OP_READ:
 		case BLKIF_OP_WRITE:
-			if (unlikely(bret->status != BLKIF_RSP_OKAY))
-				dev_dbg(&info->xbdev->dev, "Bad return from blkdev data "
-					"request: %x\n", bret->status);
+			if (unlikely(bret.status != BLKIF_RSP_OKAY))
+				dev_dbg_ratelimited(&info->xbdev->dev,
+					"Bad return from blkdev data request: %#x\n",
+					bret.status);
 
 			break;
 		default:
@@ -1612,6 +1646,14 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 	spin_unlock_irqrestore(&rinfo->ring_lock, flags);
 
 	return IRQ_HANDLED;
+
+ err:
+	info->connected = BLKIF_STATE_ERROR;
+
+	spin_unlock_irqrestore(&rinfo->ring_lock, flags);
+
+	pr_alert("%s disabled for further use\n", info->gd->disk_name);
+	return IRQ_HANDLED;
 }
 
 

drivers/pci/xen-pcifront.c

@@ -115,7 +115,7 @@ static int do_pci_op(struct pcifront_device *pdev, struct xen_pci_op *op)
 	struct xen_pci_op *active_op = &pdev->sh_info->op;
 	unsigned long irq_flags;
 	evtchn_port_t port = pdev->evtchn;
-	unsigned irq = pdev->irq;
+	unsigned int irq = pdev->irq;
 	s64 ns, ns_timeout;
 
 	spin_lock_irqsave(&pdev->sh_info_lock, irq_flags);
@@ -153,10 +153,10 @@ static int do_pci_op(struct pcifront_device *pdev, struct xen_pci_op *op)
 	}
 
 	/*
-	* We might lose backend service request since we
-	* reuse same evtchn with pci_conf backend response. So re-schedule
-	* aer pcifront service.
-	*/
+	 * We might lose backend service request since we
+	 * reuse same evtchn with pci_conf backend response. So re-schedule
+	 * aer pcifront service.
+	 */
 	if (test_bit(_XEN_PCIB_active,
 			(unsigned long *)&pdev->sh_info->flags)) {
 		dev_err(&pdev->xdev->dev,
@@ -414,7 +414,8 @@ static int pcifront_scan_bus(struct pcifront_device *pdev,
 	struct pci_dev *d;
 	unsigned int devfn;
 
-	/* Scan the bus for functions and add.
+	/*
+	 * Scan the bus for functions and add.
 	 * We omit handling of PCI bridge attachment because pciback prevents
 	 * bridges from being exported.
 	 */
@@ -492,8 +493,10 @@ static int pcifront_scan_root(struct pcifront_device *pdev,
 
 	list_add(&bus_entry->list, &pdev->root_buses);
 
-	/* pci_scan_root_bus skips devices which do not have a
-	* devfn==0. The pcifront_scan_bus enumerates all devfn. */
+	/*
+	 * pci_scan_root_bus skips devices which do not have a
+	 * devfn==0. The pcifront_scan_bus enumerates all devfn.
+	 */
 	err = pcifront_scan_bus(pdev, domain, bus, b);
 
 	/* Claim resources before going "live" with our devices */
@@ -651,8 +654,10 @@ static void pcifront_do_aer(struct work_struct *data)
 	pci_channel_state_t state =
 		(pci_channel_state_t)pdev->sh_info->aer_op.err;
 
-	/*If a pci_conf op is in progress,
-		we have to wait until it is done before service aer op*/
+	/*
+	 * If a pci_conf op is in progress, we have to wait until it is done
+	 * before service aer op
+	 */
 	dev_dbg(&pdev->xdev->dev,
 		"pcifront service aer bus %x devfn %x\n",
 		pdev->sh_info->aer_op.bus, pdev->sh_info->aer_op.devfn);
@@ -676,6 +681,7 @@ static void pcifront_do_aer(struct work_struct *data)
 static irqreturn_t pcifront_handler_aer(int irq, void *dev)
 {
 	struct pcifront_device *pdev = dev;
+
 	schedule_pcifront_aer_op(pdev);
 	return IRQ_HANDLED;
 }
@@ -1027,6 +1033,7 @@ static int pcifront_detach_devices(struct pcifront_device *pdev)
 	/* Find devices being detached and remove them. */
 	for (i = 0; i < num_devs; i++) {
 		int l, state;
+
 		l = snprintf(str, sizeof(str), "state-%d", i);
 		if (unlikely(l >= (sizeof(str) - 1))) {
 			err = -ENOMEM;
@@ -1078,7 +1085,7 @@ static int pcifront_detach_devices(struct pcifront_device *pdev)
 	return err;
 }
 
-static void __ref pcifront_backend_changed(struct xenbus_device *xdev,
+static void pcifront_backend_changed(struct xenbus_device *xdev,
 						  enum xenbus_state be_state)
 {
 	struct pcifront_device *pdev = dev_get_drvdata(&xdev->dev);
@@ -1137,6 +1144,7 @@ static int pcifront_xenbus_probe(struct xenbus_device *xdev,
 static int pcifront_xenbus_remove(struct xenbus_device *xdev)
 {
 	struct pcifront_device *pdev = dev_get_drvdata(&xdev->dev);
+
 	if (pdev)
 		free_pdev(pdev);
 

drivers/xen/features.c

@@ -9,13 +9,26 @@
 #include <linux/types.h>
 #include <linux/cache.h>
 #include <linux/export.h>
+#include <linux/printk.h>
 
 #include <asm/xen/hypercall.h>
 
+#include <xen/xen.h>
 #include <xen/interface/xen.h>
 #include <xen/interface/version.h>
 #include <xen/features.h>
 
+/*
+ * Linux kernel expects at least Xen 4.0.
+ *
+ * Assume some features to be available for that reason (depending on guest
+ * mode, of course).
+ */
+#define chk_required_feature(f) {					\
+		if (!xen_feature(f))					\
+			panic("Xen: feature %s not available!\n", #f);	\
+	}
+
 u8 xen_features[XENFEAT_NR_SUBMAPS * 32] __read_mostly;
 EXPORT_SYMBOL_GPL(xen_features);
 
@@ -31,4 +44,9 @@ void xen_setup_features(void)
 		for (j = 0; j < 32; j++)
 			xen_features[i * 32 + j] = !!(fi.submap & 1<<j);
 	}
+
+	if (xen_pv_domain()) {
+		chk_required_feature(XENFEAT_mmu_pt_update_preserve_ad);
+		chk_required_feature(XENFEAT_gnttab_map_avail_bits);
+	}
 }

drivers/xen/gntdev.c

@@ -266,20 +266,13 @@ static int find_grant_ptes(pte_t *pte, unsigned long addr, void *data)
 {
 	struct gntdev_grant_map *map = data;
 	unsigned int pgnr = (addr - map->vma->vm_start) >> PAGE_SHIFT;
-	int flags = map->flags | GNTMAP_application_map | GNTMAP_contains_pte;
+	int flags = map->flags | GNTMAP_application_map | GNTMAP_contains_pte |
+		    (1 << _GNTMAP_guest_avail0);
 	u64 pte_maddr;
 
 	BUG_ON(pgnr >= map->count);
 	pte_maddr = arbitrary_virt_to_machine(pte).maddr;
 
-	/*
-	 * Set the PTE as special to force get_user_pages_fast() fall
-	 * back to the slow path.  If this is not supported as part of
-	 * the grant map, it will be done afterwards.
-	 */
-	if (xen_feature(XENFEAT_gnttab_map_avail_bits))
-		flags |= (1 << _GNTMAP_guest_avail0);
-
 	gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, flags,
 			  map->grants[pgnr].ref,
 			  map->grants[pgnr].domid);
@@ -288,14 +281,6 @@ static int find_grant_ptes(pte_t *pte, unsigned long addr, void *data)
 	return 0;
 }
 
-#ifdef CONFIG_X86
-static int set_grant_ptes_as_special(pte_t *pte, unsigned long addr, void *data)
-{
-	set_pte_at(current->mm, addr, pte, pte_mkspecial(*pte));
-	return 0;
-}
-#endif
-
 int gntdev_map_grant_pages(struct gntdev_grant_map *map)
 {
 	int i, err = 0;
@@ -1055,23 +1040,6 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
 		err = vm_map_pages_zero(vma, map->pages, map->count);
 		if (err)
 			goto out_put_map;
-	} else {
-#ifdef CONFIG_X86
-		/*
-		 * If the PTEs were not made special by the grant map
-		 * hypercall, do so here.
-		 *
-		 * This is racy since the mapping is already visible
-		 * to userspace but userspace should be well-behaved
-		 * enough to not touch it until the mmap() call
-		 * returns.
-		 */
-		if (!xen_feature(XENFEAT_gnttab_map_avail_bits)) {
-			apply_to_page_range(vma->vm_mm, vma->vm_start,
-					    vma->vm_end - vma->vm_start,
-					    set_grant_ptes_as_special, NULL);
-		}
-#endif
 	}
 
 	return 0;

drivers/xen/xenbus/xenbus_client.c

@@ -542,8 +542,7 @@ static int __xenbus_map_ring(struct xenbus_device *dev,
 		}
 	}
 
-	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, info->unmap, j))
-		BUG();
+	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, info->unmap, j));
 
 	*leaked = false;
 	for (i = 0; i < j; i++) {
@@ -581,8 +580,7 @@ static int xenbus_unmap_ring(struct xenbus_device *dev, grant_handle_t *handles,
 		gnttab_set_unmap_op(&unmap[i], vaddrs[i],
 				    GNTMAP_host_map, handles[i]);
 
-	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i))
-		BUG();
+	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i));
 
 	err = GNTST_okay;
 	for (i = 0; i < nr_handles; i++) {
@@ -778,8 +776,7 @@ static int xenbus_unmap_ring_pv(struct xenbus_device *dev, void *vaddr)
 		unmap[i].handle = node->handles[i];
 	}
 
-	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i))
-		BUG();
+	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i));
 
 	err = GNTST_okay;
 	leaked = false;