[PATCH v2 0/5] xen: grant table interface v2 support

[PATCH v2 0/5] xen: grant table interface v2 support

[Juergen Gross]

In order to support Linux to run as a pv guest on machines with huge
memory (>16TB) or as a hvm guest with more than 16TB of memory the
kernel has to support grant table interface v2, as v1 is limited to
32 bit frame numbers.

This series re-adds that support (it has been removed in 2015) and
restricts usage of v2 to the features of v1 in order to support
migration to hosts which only support v1.

V2 is selected only in the following cases:
- the user has specified v2 via module parameter
- in a pv guest if the maximum possible memory address of the host is
  above 16TB (memory hotplug taken into account)
- in a hvm guest if the maximum guest memory address is above 16TB
  (again with memory hotplug taken into account)

Changes in V2:
- patch 2: remove update_trans_entry() from gnttab_ops (Boris Ostrovsky)
- added new patch 4
- patch 5: use cpuid on pv and max_possible_pfn on hvm for version select

Juergen Gross (5):
  xen: re-introduce support for grant v2 interface
  xen: limit grant v2 interface to the v1 functionality
  xen: add grant interface version dependent constants to gnttab_ops
  xen: update arch/x86/include/asm/xen/cpuid.h
  xen: select grant interface version

 arch/arm/xen/grant-table.c       |   9 +-
 arch/x86/include/asm/xen/cpuid.h |  42 +++++--
 arch/x86/xen/grant-table.c       |  60 +++++++++-
 drivers/xen/grant-table.c        | 244 +++++++++++++++++++++++++++++++++++----
 include/xen/grant_table.h        |   5 +-
 5 files changed, 318 insertions(+), 42 deletions(-)

-- 
2.12.3

[PATCH v2 1/5] xen: re-introduce support for grant v2 interface

[Juergen Gross]

The grant v2 support was removed from the kernel with
commit 438b33c7145ca8a5131a30c36d8f59bce119a19a ("xen/grant-table:
remove support for V2 tables") as the higher memory footprint of v2
grants resulted in less grants being possible for a kernel compared
to the v1 grant interface.

As machines with more than 16TB of memory are expected to be more
common in the near future support of grant v2 is mandatory in order
to be able to run a Xen pv domain at any memory location.

So re-add grant v2 support basically by reverting above commit.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/arm/xen/grant-table.c |   9 +-
 arch/x86/xen/grant-table.c |  60 ++++++++-
 drivers/xen/grant-table.c  | 312 ++++++++++++++++++++++++++++++++++++++++++++-
 include/xen/grant_table.h  |  30 ++++-
 4 files changed, 398 insertions(+), 13 deletions(-)

diff --git a/arch/arm/xen/grant-table.c b/arch/arm/xen/grant-table.c
index e43791829ace..91cf08ba1e95 100644
--- a/arch/arm/xen/grant-table.c
+++ b/arch/arm/xen/grant-table.c
@@ -45,7 +45,14 @@ void arch_gnttab_unmap(void *shared, unsigned long nr_gframes)
 	return;
 }
 
-int arch_gnttab_init(unsigned long nr_shared)
+int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
+			   unsigned long max_nr_gframes,
+			   grant_status_t **__shared)
+{
+	return -ENOSYS;
+}
+
+int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status)
 {
 	return 0;
 }
diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
index 809b6c812654..92ccc718152d 100644
--- a/arch/x86/xen/grant-table.c
+++ b/arch/x86/xen/grant-table.c
@@ -49,7 +49,7 @@
 static struct gnttab_vm_area {
 	struct vm_struct *area;
 	pte_t **ptes;
-} gnttab_shared_vm_area;
+} gnttab_shared_vm_area, gnttab_status_vm_area;
 
 int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes,
 			   unsigned long max_nr_gframes,
@@ -73,16 +73,43 @@ int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes,
 	return 0;
 }
 
+int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
+			   unsigned long max_nr_gframes,
+			   grant_status_t **__shared)
+{
+	grant_status_t *shared = *__shared;
+	unsigned long addr;
+	unsigned long i;
+
+	if (shared == NULL)
+		*__shared = shared = gnttab_status_vm_area.area->addr;
+
+	addr = (unsigned long)shared;
+
+	for (i = 0; i < nr_gframes; i++) {
+		set_pte_at(&init_mm, addr, gnttab_status_vm_area.ptes[i],
+			   mfn_pte(frames[i], PAGE_KERNEL));
+		addr += PAGE_SIZE;
+	}
+
+	return 0;
+}
+
 void arch_gnttab_unmap(void *shared, unsigned long nr_gframes)
 {
+	pte_t **ptes;
 	unsigned long addr;
 	unsigned long i;
 
+	if (shared == gnttab_status_vm_area.area->addr)
+		ptes = gnttab_status_vm_area.ptes;
+	else
+		ptes = gnttab_shared_vm_area.ptes;
+
 	addr = (unsigned long)shared;
 
 	for (i = 0; i < nr_gframes; i++) {
-		set_pte_at(&init_mm, addr, gnttab_shared_vm_area.ptes[i],
-			   __pte(0));
+		set_pte_at(&init_mm, addr, ptes[i], __pte(0));
 		addr += PAGE_SIZE;
 	}
 }
@@ -102,12 +129,35 @@ static int arch_gnttab_valloc(struct gnttab_vm_area *area, unsigned nr_frames)
 	return 0;
 }
 
-int arch_gnttab_init(unsigned long nr_shared)
+static void arch_gnttab_vfree(struct gnttab_vm_area *area)
 {
+	free_vm_area(area->area);
+	kfree(area->ptes);
+}
+
+int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status)
+{
+	int ret;
+
 	if (!xen_pv_domain())
 		return 0;
 
-	return arch_gnttab_valloc(&gnttab_shared_vm_area, nr_shared);
+	ret = arch_gnttab_valloc(&gnttab_shared_vm_area, nr_shared);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Always allocate the space for the status frames in case
+	 * we're migrated to a host with V2 support.
+	 */
+	ret = arch_gnttab_valloc(&gnttab_status_vm_area, nr_status);
+	if (ret < 0)
+		goto err;
+
+	return 0;
+err:
+	arch_gnttab_vfree(&gnttab_shared_vm_area);
+	return -ENOMEM;
 }
 
 #ifdef CONFIG_XEN_PVH
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 2c6a9114d332..65c4bdb0b463 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -71,6 +71,7 @@ struct grant_frames xen_auto_xlat_grant_frames;
 
 static union {
 	struct grant_entry_v1 *v1;
+	union grant_entry_v2 *v2;
 	void *addr;
 } gnttab_shared;
 
@@ -121,6 +122,29 @@ struct gnttab_ops {
 	 * by bit operations.
 	 */
 	int (*query_foreign_access)(grant_ref_t ref);
+	/*
+	 * Grant a domain to access a range of bytes within the page referred by
+	 * an available grant entry. Ref parameter is reference of a grant entry
+	 * which will be sub-page accessed, domid is id of grantee domain, frame
+	 * is frame address of subpage grant, flags is grant type and flag
+	 * information, page_off is offset of the range of bytes, and length is
+	 * length of bytes to be accessed.
+	 */
+	void (*update_subpage_entry)(grant_ref_t ref, domid_t domid,
+				     unsigned long frame, int flags,
+				     unsigned page_off, unsigned length);
+	/*
+	 * Redirect an available grant entry on domain A to another grant
+	 * reference of domain B, then allow domain C to use grant reference
+	 * of domain B transitively. Ref parameter is an available grant entry
+	 * reference on domain A, domid is id of domain C which accesses grant
+	 * entry transitively, flags is grant type and flag information,
+	 * trans_domid is id of domain B whose grant entry is finally accessed
+	 * transitively, trans_gref is grant entry transitive reference of
+	 * domain B.
+	 */
+	void (*update_trans_entry)(grant_ref_t ref, domid_t domid, int flags,
+				   domid_t trans_domid, grant_ref_t trans_gref);
 };
 
 struct unmap_refs_callback_data {
@@ -130,6 +154,9 @@ struct unmap_refs_callback_data {
 
 static const struct gnttab_ops *gnttab_interface;
 
+/* This reflects status of grant entries, so act as a global value. */
+static grant_status_t *grstatus;
+
 static int grant_table_version;
 static int grefs_per_grant_frame;
 
@@ -138,6 +165,7 @@ static struct gnttab_free_callback *gnttab_free_callback_list;
 static int gnttab_expand(unsigned int req_entries);
 
 #define RPP (PAGE_SIZE / sizeof(grant_ref_t))
+#define SPP (PAGE_SIZE / sizeof(grant_status_t))
 
 static inline grant_ref_t *__gnttab_entry(grant_ref_t entry)
 {
@@ -210,7 +238,7 @@ static void put_free_entry(grant_ref_t ref)
 }
 
 /*
- * Following applies to gnttab_update_entry_v1.
+ * Following applies to gnttab_update_entry_v1 and gnttab_update_entry_v2.
  * Introducing a valid entry into the grant table:
  *  1. Write ent->domid.
  *  2. Write ent->frame:
@@ -229,6 +257,15 @@ static void gnttab_update_entry_v1(grant_ref_t ref, domid_t domid,
 	gnttab_shared.v1[ref].flags = flags;
 }
 
+static void gnttab_update_entry_v2(grant_ref_t ref, domid_t domid,
+				   unsigned long frame, unsigned int flags)
+{
+	gnttab_shared.v2[ref].hdr.domid = domid;
+	gnttab_shared.v2[ref].full_page.frame = frame;
+	wmb();	/* Hypervisor concurrent accesses. */
+	gnttab_shared.v2[ref].hdr.flags = GTF_permit_access | flags;
+}
+
 /*
  * Public grant-issuing interface functions
  */
@@ -255,11 +292,132 @@ int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
 }
 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
 
+static void gnttab_update_subpage_entry_v2(grant_ref_t ref, domid_t domid,
+					   unsigned long frame, int flags,
+					   unsigned page_off, unsigned length)
+{
+	gnttab_shared.v2[ref].sub_page.frame = frame;
+	gnttab_shared.v2[ref].sub_page.page_off = page_off;
+	gnttab_shared.v2[ref].sub_page.length = length;
+	gnttab_shared.v2[ref].hdr.domid = domid;
+	wmb();
+	gnttab_shared.v2[ref].hdr.flags =
+				GTF_permit_access | GTF_sub_page | flags;
+}
+
+int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref, domid_t domid,
+					    unsigned long frame, int flags,
+					    unsigned page_off,
+					    unsigned length)
+{
+	if (flags & (GTF_accept_transfer | GTF_reading |
+		     GTF_writing | GTF_transitive))
+		return -EPERM;
+
+	if (gnttab_interface->update_subpage_entry == NULL)
+		return -ENOSYS;
+
+	gnttab_interface->update_subpage_entry(ref, domid, frame, flags,
+					       page_off, length);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage_ref);
+
+int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,
+					int flags, unsigned page_off,
+					unsigned length)
+{
+	int ref, rc;
+
+	ref = get_free_entries(1);
+	if (unlikely(ref < 0))
+		return -ENOSPC;
+
+	rc = gnttab_grant_foreign_access_subpage_ref(ref, domid, frame, flags,
+						     page_off, length);
+	if (rc < 0) {
+		put_free_entry(ref);
+		return rc;
+	}
+
+	return ref;
+}
+EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage);
+
+bool gnttab_subpage_grants_available(void)
+{
+	return gnttab_interface->update_subpage_entry != NULL;
+}
+EXPORT_SYMBOL_GPL(gnttab_subpage_grants_available);
+
+static void gnttab_update_trans_entry_v2(grant_ref_t ref, domid_t domid,
+					 int flags, domid_t trans_domid,
+					 grant_ref_t trans_gref)
+{
+	gnttab_shared.v2[ref].transitive.trans_domid = trans_domid;
+	gnttab_shared.v2[ref].transitive.gref = trans_gref;
+	gnttab_shared.v2[ref].hdr.domid = domid;
+	wmb();
+	gnttab_shared.v2[ref].hdr.flags =
+				GTF_permit_access | GTF_transitive | flags;
+}
+
+int gnttab_grant_foreign_access_trans_ref(grant_ref_t ref, domid_t domid,
+					  int flags, domid_t trans_domid,
+					  grant_ref_t trans_gref)
+{
+	if (flags & (GTF_accept_transfer | GTF_reading |
+		     GTF_writing | GTF_sub_page))
+		return -EPERM;
+
+	if (gnttab_interface->update_trans_entry == NULL)
+		return -ENOSYS;
+
+	gnttab_interface->update_trans_entry(ref, domid, flags, trans_domid,
+					     trans_gref);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans_ref);
+
+int gnttab_grant_foreign_access_trans(domid_t domid, int flags,
+				      domid_t trans_domid,
+				      grant_ref_t trans_gref)
+{
+	int ref, rc;
+
+	ref = get_free_entries(1);
+	if (unlikely(ref < 0))
+		return -ENOSPC;
+
+	rc = gnttab_grant_foreign_access_trans_ref(ref, domid, flags,
+						   trans_domid, trans_gref);
+	if (rc < 0) {
+		put_free_entry(ref);
+		return rc;
+	}
+
+	return ref;
+}
+EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans);
+
+bool gnttab_trans_grants_available(void)
+{
+	return gnttab_interface->update_trans_entry != NULL;
+}
+EXPORT_SYMBOL_GPL(gnttab_trans_grants_available);
+
 static int gnttab_query_foreign_access_v1(grant_ref_t ref)
 {
 	return gnttab_shared.v1[ref].flags & (GTF_reading|GTF_writing);
 }
 
+static int gnttab_query_foreign_access_v2(grant_ref_t ref)
+{
+	return grstatus[ref] & (GTF_reading|GTF_writing);
+}
+
 int gnttab_query_foreign_access(grant_ref_t ref)
 {
 	return gnttab_interface->query_foreign_access(ref);
@@ -282,6 +440,29 @@ static int gnttab_end_foreign_access_ref_v1(grant_ref_t ref, int readonly)
 	return 1;
 }
 
+static int gnttab_end_foreign_access_ref_v2(grant_ref_t ref, int readonly)
+{
+	gnttab_shared.v2[ref].hdr.flags = 0;
+	mb();	/* Concurrent access by hypervisor. */
+	if (grstatus[ref] & (GTF_reading|GTF_writing)) {
+		return 0;
+	} else {
+		/*
+		 * The read of grstatus needs to have acquire semantics.
+		 *  On x86, reads already have that, and we just need to
+		 * protect against compiler reorderings.
+		 * On other architectures we may need a full barrier.
+		 */
+#ifdef CONFIG_X86
+		barrier();
+#else
+		mb();
+#endif
+	}
+
+	return 1;
+}
+
 static inline int _gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
 {
 	return gnttab_interface->end_foreign_access_ref(ref, readonly);
@@ -442,6 +623,37 @@ static unsigned long gnttab_end_foreign_transfer_ref_v1(grant_ref_t ref)
 	return frame;
 }
 
+static unsigned long gnttab_end_foreign_transfer_ref_v2(grant_ref_t ref)
+{
+	unsigned long frame;
+	u16           flags;
+	u16          *pflags;
+
+	pflags = &gnttab_shared.v2[ref].hdr.flags;
+
+	/*
+	 * If a transfer is not even yet started, try to reclaim the grant
+	 * reference and return failure (== 0).
+	 */
+	while (!((flags = *pflags) & GTF_transfer_committed)) {
+		if (sync_cmpxchg(pflags, flags, 0) == flags)
+			return 0;
+		cpu_relax();
+	}
+
+	/* If a transfer is in progress then wait until it is completed. */
+	while (!(flags & GTF_transfer_completed)) {
+		flags = *pflags;
+		cpu_relax();
+	}
+
+	rmb();  /* Read the frame number /after/ reading completion status. */
+	frame = gnttab_shared.v2[ref].full_page.frame;
+	BUG_ON(frame == 0);
+
+	return frame;
+}
+
 unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref)
 {
 	return gnttab_interface->end_foreign_transfer_ref(ref);
@@ -938,6 +1150,12 @@ int gnttab_unmap_refs_sync(struct gntab_unmap_queue_data *item)
 }
 EXPORT_SYMBOL_GPL(gnttab_unmap_refs_sync);
 
+static unsigned int nr_status_frames(unsigned int nr_grant_frames)
+{
+	BUG_ON(grefs_per_grant_frame == 0);
+	return (nr_grant_frames * grefs_per_grant_frame + SPP - 1) / SPP;
+}
+
 static int gnttab_map_frames_v1(xen_pfn_t *frames, unsigned int nr_gframes)
 {
 	int rc;
@@ -955,6 +1173,55 @@ static void gnttab_unmap_frames_v1(void)
 	arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
 }
 
+static int gnttab_map_frames_v2(xen_pfn_t *frames, unsigned int nr_gframes)
+{
+	uint64_t *sframes;
+	unsigned int nr_sframes;
+	struct gnttab_get_status_frames getframes;
+	int rc;
+
+	nr_sframes = nr_status_frames(nr_gframes);
+
+	/* No need for kzalloc as it is initialized in following hypercall
+	 * GNTTABOP_get_status_frames.
+	 */
+	sframes = kmalloc_array(nr_sframes, sizeof(uint64_t), GFP_ATOMIC);
+	if (!sframes)
+		return -ENOMEM;
+
+	getframes.dom        = DOMID_SELF;
+	getframes.nr_frames  = nr_sframes;
+	set_xen_guest_handle(getframes.frame_list, sframes);
+
+	rc = HYPERVISOR_grant_table_op(GNTTABOP_get_status_frames,
+				       &getframes, 1);
+	if (rc == -ENOSYS) {
+		kfree(sframes);
+		return -ENOSYS;
+	}
+
+	BUG_ON(rc || getframes.status);
+
+	rc = arch_gnttab_map_status(sframes, nr_sframes,
+				    nr_status_frames(gnttab_max_grant_frames()),
+				    &grstatus);
+	BUG_ON(rc);
+	kfree(sframes);
+
+	rc = arch_gnttab_map_shared(frames, nr_gframes,
+				    gnttab_max_grant_frames(),
+				    &gnttab_shared.addr);
+	BUG_ON(rc);
+
+	return 0;
+}
+
+static void gnttab_unmap_frames_v2(void)
+{
+	arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
+	arch_gnttab_unmap(grstatus, nr_status_frames(nr_grant_frames));
+}
+
 static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
 {
 	struct gnttab_setup_table setup;
@@ -1022,13 +1289,45 @@ static const struct gnttab_ops gnttab_v1_ops = {
 	.query_foreign_access		= gnttab_query_foreign_access_v1,
 };
 
+static const struct gnttab_ops gnttab_v2_ops = {
+	.map_frames			= gnttab_map_frames_v2,
+	.unmap_frames			= gnttab_unmap_frames_v2,
+	.update_entry			= gnttab_update_entry_v2,
+	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v2,
+	.end_foreign_transfer_ref	= gnttab_end_foreign_transfer_ref_v2,
+	.query_foreign_access		= gnttab_query_foreign_access_v2,
+	.update_subpage_entry		= gnttab_update_subpage_entry_v2,
+	.update_trans_entry		= gnttab_update_trans_entry_v2,
+};
+
 static void gnttab_request_version(void)
 {
-	/* Only version 1 is used, which will always be available. */
-	grant_table_version = 1;
-	grefs_per_grant_frame = XEN_PAGE_SIZE / sizeof(struct grant_entry_v1);
-	gnttab_interface = &gnttab_v1_ops;
+	int rc;
+	struct gnttab_set_version gsv;
 
+	gsv.version = 1;
+
+	rc = HYPERVISOR_grant_table_op(GNTTABOP_set_version, &gsv, 1);
+	if (rc == 0 && gsv.version == 2) {
+		grant_table_version = 2;
+		grefs_per_grant_frame = XEN_PAGE_SIZE /
+					sizeof(union grant_entry_v2);
+		gnttab_interface = &gnttab_v2_ops;
+	} else if (grant_table_version == 2) {
+		/*
+		 * If we've already used version 2 features,
+		 * but then suddenly discover that they're not
+		 * available (e.g. migrating to an older
+		 * version of Xen), almost unbounded badness
+		 * can happen.
+		 */
+		panic("we need grant tables version 2, but only version 1 is available");
+	} else {
+		grant_table_version = 1;
+		grefs_per_grant_frame = XEN_PAGE_SIZE /
+					sizeof(struct grant_entry_v1);
+		gnttab_interface = &gnttab_v1_ops;
+	}
 	pr_info("Grant tables using version %d layout\n", grant_table_version);
 }
 
@@ -1122,7 +1421,8 @@ int gnttab_init(void)
 		}
 	}
 
-	ret = arch_gnttab_init(max_nr_grant_frames);
+	ret = arch_gnttab_init(max_nr_grant_frames,
+			       nr_status_frames(max_nr_grant_frames));
 	if (ret < 0)
 		goto ini_nomem;
 
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index 34b1379f9777..dd6c7a32ee32 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -84,6 +84,24 @@ int gnttab_resume(void);
 
 int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
 				int readonly);
+int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,
+					int flags, unsigned page_off,
+					unsigned length);
+int gnttab_grant_foreign_access_trans(domid_t domid, int flags,
+				      domid_t trans_domid,
+				      grant_ref_t trans_gref);
+
+/*
+ * Are sub-page grants available on this version of Xen?  Returns true if they
+ * are, and false if they're not.
+ */
+bool gnttab_subpage_grants_available(void);
+
+/*
+ * Are transitive grants available on this version of Xen?  Returns true if they
+ * are, and false if they're not.
+ */
+bool gnttab_trans_grants_available(void);
 
 /*
  * End access through the given grant reference, iff the grant entry is no
@@ -130,6 +148,13 @@ void gnttab_cancel_free_callback(struct gnttab_free_callback *callback);
 
 void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
 				     unsigned long frame, int readonly);
+int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref, domid_t domid,
+					    unsigned long frame, int flags,
+					    unsigned page_off,
+					    unsigned length);
+int gnttab_grant_foreign_access_trans_ref(grant_ref_t ref, domid_t domid,
+					  int flags, domid_t trans_domid,
+					  grant_ref_t trans_gref);
 
 /* Give access to the first 4K of the page */
 static inline void gnttab_page_grant_foreign_access_ref_one(
@@ -174,10 +199,13 @@ gnttab_set_unmap_op(struct gnttab_unmap_grant_ref *unmap, phys_addr_t addr,
 	unmap->dev_bus_addr = 0;
 }
 
-int arch_gnttab_init(unsigned long nr_shared);
+int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status);
 int arch_gnttab_map_shared(xen_pfn_t *frames, unsigned long nr_gframes,
 			   unsigned long max_nr_gframes,
 			   void **__shared);
+int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
+			   unsigned long max_nr_gframes,
+			   grant_status_t **__shared);
 void arch_gnttab_unmap(void *shared, unsigned long nr_gframes);
 
 struct grant_frames {
-- 
2.12.3

[PATCH v2 2/5] xen: limit grant v2 interface to the v1 functionality

[Juergen Gross]

As there is currently no user for sub-page grants or transient grants
remove that functionality. This at once makes it possible to switch
from grant v2 to grant v1 without restrictions, as there is no loss of
functionality other than the limited frame number width related to
the switch.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2:
- remove update_trans_entry() from gnttab_ops (Boris Ostrovsky)
---
 drivers/xen/grant-table.c | 150 ----------------------------------------------
 include/xen/grant_table.h |  25 --------
 2 files changed, 175 deletions(-)

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 65c4bdb0b463..db6a1b9efd11 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -122,29 +122,6 @@ struct gnttab_ops {
 	 * by bit operations.
 	 */
 	int (*query_foreign_access)(grant_ref_t ref);
-	/*
-	 * Grant a domain to access a range of bytes within the page referred by
-	 * an available grant entry. Ref parameter is reference of a grant entry
-	 * which will be sub-page accessed, domid is id of grantee domain, frame
-	 * is frame address of subpage grant, flags is grant type and flag
-	 * information, page_off is offset of the range of bytes, and length is
-	 * length of bytes to be accessed.
-	 */
-	void (*update_subpage_entry)(grant_ref_t ref, domid_t domid,
-				     unsigned long frame, int flags,
-				     unsigned page_off, unsigned length);
-	/*
-	 * Redirect an available grant entry on domain A to another grant
-	 * reference of domain B, then allow domain C to use grant reference
-	 * of domain B transitively. Ref parameter is an available grant entry
-	 * reference on domain A, domid is id of domain C which accesses grant
-	 * entry transitively, flags is grant type and flag information,
-	 * trans_domid is id of domain B whose grant entry is finally accessed
-	 * transitively, trans_gref is grant entry transitive reference of
-	 * domain B.
-	 */
-	void (*update_trans_entry)(grant_ref_t ref, domid_t domid, int flags,
-				   domid_t trans_domid, grant_ref_t trans_gref);
 };
 
 struct unmap_refs_callback_data {
@@ -292,122 +269,6 @@ int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
 }
 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
 
-static void gnttab_update_subpage_entry_v2(grant_ref_t ref, domid_t domid,
-					   unsigned long frame, int flags,
-					   unsigned page_off, unsigned length)
-{
-	gnttab_shared.v2[ref].sub_page.frame = frame;
-	gnttab_shared.v2[ref].sub_page.page_off = page_off;
-	gnttab_shared.v2[ref].sub_page.length = length;
-	gnttab_shared.v2[ref].hdr.domid = domid;
-	wmb();
-	gnttab_shared.v2[ref].hdr.flags =
-				GTF_permit_access | GTF_sub_page | flags;
-}
-
-int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref, domid_t domid,
-					    unsigned long frame, int flags,
-					    unsigned page_off,
-					    unsigned length)
-{
-	if (flags & (GTF_accept_transfer | GTF_reading |
-		     GTF_writing | GTF_transitive))
-		return -EPERM;
-
-	if (gnttab_interface->update_subpage_entry == NULL)
-		return -ENOSYS;
-
-	gnttab_interface->update_subpage_entry(ref, domid, frame, flags,
-					       page_off, length);
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage_ref);
-
-int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,
-					int flags, unsigned page_off,
-					unsigned length)
-{
-	int ref, rc;
-
-	ref = get_free_entries(1);
-	if (unlikely(ref < 0))
-		return -ENOSPC;
-
-	rc = gnttab_grant_foreign_access_subpage_ref(ref, domid, frame, flags,
-						     page_off, length);
-	if (rc < 0) {
-		put_free_entry(ref);
-		return rc;
-	}
-
-	return ref;
-}
-EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage);
-
-bool gnttab_subpage_grants_available(void)
-{
-	return gnttab_interface->update_subpage_entry != NULL;
-}
-EXPORT_SYMBOL_GPL(gnttab_subpage_grants_available);
-
-static void gnttab_update_trans_entry_v2(grant_ref_t ref, domid_t domid,
-					 int flags, domid_t trans_domid,
-					 grant_ref_t trans_gref)
-{
-	gnttab_shared.v2[ref].transitive.trans_domid = trans_domid;
-	gnttab_shared.v2[ref].transitive.gref = trans_gref;
-	gnttab_shared.v2[ref].hdr.domid = domid;
-	wmb();
-	gnttab_shared.v2[ref].hdr.flags =
-				GTF_permit_access | GTF_transitive | flags;
-}
-
-int gnttab_grant_foreign_access_trans_ref(grant_ref_t ref, domid_t domid,
-					  int flags, domid_t trans_domid,
-					  grant_ref_t trans_gref)
-{
-	if (flags & (GTF_accept_transfer | GTF_reading |
-		     GTF_writing | GTF_sub_page))
-		return -EPERM;
-
-	if (gnttab_interface->update_trans_entry == NULL)
-		return -ENOSYS;
-
-	gnttab_interface->update_trans_entry(ref, domid, flags, trans_domid,
-					     trans_gref);
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans_ref);
-
-int gnttab_grant_foreign_access_trans(domid_t domid, int flags,
-				      domid_t trans_domid,
-				      grant_ref_t trans_gref)
-{
-	int ref, rc;
-
-	ref = get_free_entries(1);
-	if (unlikely(ref < 0))
-		return -ENOSPC;
-
-	rc = gnttab_grant_foreign_access_trans_ref(ref, domid, flags,
-						   trans_domid, trans_gref);
-	if (rc < 0) {
-		put_free_entry(ref);
-		return rc;
-	}
-
-	return ref;
-}
-EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans);
-
-bool gnttab_trans_grants_available(void)
-{
-	return gnttab_interface->update_trans_entry != NULL;
-}
-EXPORT_SYMBOL_GPL(gnttab_trans_grants_available);
-
 static int gnttab_query_foreign_access_v1(grant_ref_t ref)
 {
 	return gnttab_shared.v1[ref].flags & (GTF_reading|GTF_writing);
@@ -1296,8 +1157,6 @@ static const struct gnttab_ops gnttab_v2_ops = {
 	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v2,
 	.end_foreign_transfer_ref	= gnttab_end_foreign_transfer_ref_v2,
 	.query_foreign_access		= gnttab_query_foreign_access_v2,
-	.update_subpage_entry		= gnttab_update_subpage_entry_v2,
-	.update_trans_entry		= gnttab_update_trans_entry_v2,
 };
 
 static void gnttab_request_version(void)
@@ -1313,15 +1172,6 @@ static void gnttab_request_version(void)
 		grefs_per_grant_frame = XEN_PAGE_SIZE /
 					sizeof(union grant_entry_v2);
 		gnttab_interface = &gnttab_v2_ops;
-	} else if (grant_table_version == 2) {
-		/*
-		 * If we've already used version 2 features,
-		 * but then suddenly discover that they're not
-		 * available (e.g. migrating to an older
-		 * version of Xen), almost unbounded badness
-		 * can happen.
-		 */
-		panic("we need grant tables version 2, but only version 1 is available");
 	} else {
 		grant_table_version = 1;
 		grefs_per_grant_frame = XEN_PAGE_SIZE /
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index dd6c7a32ee32..2e37741f6b8d 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -84,24 +84,6 @@ int gnttab_resume(void);
 
 int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
 				int readonly);
-int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,
-					int flags, unsigned page_off,
-					unsigned length);
-int gnttab_grant_foreign_access_trans(domid_t domid, int flags,
-				      domid_t trans_domid,
-				      grant_ref_t trans_gref);
-
-/*
- * Are sub-page grants available on this version of Xen?  Returns true if they
- * are, and false if they're not.
- */
-bool gnttab_subpage_grants_available(void);
-
-/*
- * Are transitive grants available on this version of Xen?  Returns true if they
- * are, and false if they're not.
- */
-bool gnttab_trans_grants_available(void);
 
 /*
  * End access through the given grant reference, iff the grant entry is no
@@ -148,13 +130,6 @@ void gnttab_cancel_free_callback(struct gnttab_free_callback *callback);
 
 void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
 				     unsigned long frame, int readonly);
-int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref, domid_t domid,
-					    unsigned long frame, int flags,
-					    unsigned page_off,
-					    unsigned length);
-int gnttab_grant_foreign_access_trans_ref(grant_ref_t ref, domid_t domid,
-					  int flags, domid_t trans_domid,
-					  grant_ref_t trans_gref);
 
 /* Give access to the first 4K of the page */
 static inline void gnttab_page_grant_foreign_access_ref_one(
-- 
2.12.3

[PATCH v2 3/5] xen: add grant interface version dependent constants to gnttab_ops

[Juergen Gross]

Instead of having multiple variables with constants like
grant_table_version or grefs_per_grant_frame add those to struct
gnttab_ops and access them just via the gnttab_interface pointer.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
 drivers/xen/grant-table.c | 73 ++++++++++++++++++++++++++++-------------------
 1 file changed, 43 insertions(+), 30 deletions(-)

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index db6a1b9efd11..573e7fe9b147 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -78,6 +78,14 @@ static union {
 /*This is a structure of function pointers for grant table*/
 struct gnttab_ops {
 	/*
+	 * Version of the grant interface.
+	 */
+	unsigned int version;
+	/*
+	 * Grant refs per grant frame.
+	 */
+	unsigned int grefs_per_grant_frame;
+	/*
 	 * Mapping a list of frames for storing grant entries. Frames parameter
 	 * is used to store grant table address when grant table being setup,
 	 * nr_gframes is the number of frames to map grant table. Returning
@@ -134,9 +142,6 @@ static const struct gnttab_ops *gnttab_interface;
 /* This reflects status of grant entries, so act as a global value. */
 static grant_status_t *grstatus;
 
-static int grant_table_version;
-static int grefs_per_grant_frame;
-
 static struct gnttab_free_callback *gnttab_free_callback_list;
 
 static int gnttab_expand(unsigned int req_entries);
@@ -636,19 +641,26 @@ void gnttab_cancel_free_callback(struct gnttab_free_callback *callback)
 }
 EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback);
 
+static unsigned int gnttab_frames(unsigned int frames, unsigned int align)
+{
+	return (frames * gnttab_interface->grefs_per_grant_frame + align - 1) /
+	       align;
+}
+
 static int grow_gnttab_list(unsigned int more_frames)
 {
 	unsigned int new_nr_grant_frames, extra_entries, i;
 	unsigned int nr_glist_frames, new_nr_glist_frames;
+	unsigned int grefs_per_frame;
 
-	BUG_ON(grefs_per_grant_frame == 0);
+	BUG_ON(gnttab_interface == NULL);
+	grefs_per_frame = gnttab_interface->grefs_per_grant_frame;
 
 	new_nr_grant_frames = nr_grant_frames + more_frames;
-	extra_entries       = more_frames * grefs_per_grant_frame;
+	extra_entries = more_frames * grefs_per_frame;
 
-	nr_glist_frames = (nr_grant_frames * grefs_per_grant_frame + RPP - 1) / RPP;
-	new_nr_glist_frames =
-		(new_nr_grant_frames * grefs_per_grant_frame + RPP - 1) / RPP;
+	nr_glist_frames = gnttab_frames(nr_grant_frames, RPP);
+	new_nr_glist_frames = gnttab_frames(new_nr_grant_frames, RPP);
 	for (i = nr_glist_frames; i < new_nr_glist_frames; i++) {
 		gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC);
 		if (!gnttab_list[i])
@@ -656,12 +668,12 @@ static int grow_gnttab_list(unsigned int more_frames)
 	}
 
 
-	for (i = grefs_per_grant_frame * nr_grant_frames;
-	     i < grefs_per_grant_frame * new_nr_grant_frames - 1; i++)
+	for (i = grefs_per_frame * nr_grant_frames;
+	     i < grefs_per_frame * new_nr_grant_frames - 1; i++)
 		gnttab_entry(i) = i + 1;
 
 	gnttab_entry(i) = gnttab_free_head;
-	gnttab_free_head = grefs_per_grant_frame * nr_grant_frames;
+	gnttab_free_head = grefs_per_frame * nr_grant_frames;
 	gnttab_free_count += extra_entries;
 
 	nr_grant_frames = new_nr_grant_frames;
@@ -1013,8 +1025,8 @@ EXPORT_SYMBOL_GPL(gnttab_unmap_refs_sync);
 
 static unsigned int nr_status_frames(unsigned int nr_grant_frames)
 {
-	BUG_ON(grefs_per_grant_frame == 0);
-	return (nr_grant_frames * grefs_per_grant_frame + SPP - 1) / SPP;
+	BUG_ON(gnttab_interface == NULL);
+	return gnttab_frames(nr_grant_frames, SPP);
 }
 
 static int gnttab_map_frames_v1(xen_pfn_t *frames, unsigned int nr_gframes)
@@ -1142,6 +1154,9 @@ static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
 }
 
 static const struct gnttab_ops gnttab_v1_ops = {
+	.version			= 1,
+	.grefs_per_grant_frame		= XEN_PAGE_SIZE /
+					  sizeof(struct grant_entry_v1),
 	.map_frames			= gnttab_map_frames_v1,
 	.unmap_frames			= gnttab_unmap_frames_v1,
 	.update_entry			= gnttab_update_entry_v1,
@@ -1151,6 +1166,9 @@ static const struct gnttab_ops gnttab_v1_ops = {
 };
 
 static const struct gnttab_ops gnttab_v2_ops = {
+	.version			= 2,
+	.grefs_per_grant_frame		= XEN_PAGE_SIZE /
+					  sizeof(union grant_entry_v2),
 	.map_frames			= gnttab_map_frames_v2,
 	.unmap_frames			= gnttab_unmap_frames_v2,
 	.update_entry			= gnttab_update_entry_v2,
@@ -1167,18 +1185,12 @@ static void gnttab_request_version(void)
 	gsv.version = 1;
 
 	rc = HYPERVISOR_grant_table_op(GNTTABOP_set_version, &gsv, 1);
-	if (rc == 0 && gsv.version == 2) {
-		grant_table_version = 2;
-		grefs_per_grant_frame = XEN_PAGE_SIZE /
-					sizeof(union grant_entry_v2);
+	if (rc == 0 && gsv.version == 2)
 		gnttab_interface = &gnttab_v2_ops;
-	} else {
-		grant_table_version = 1;
-		grefs_per_grant_frame = XEN_PAGE_SIZE /
-					sizeof(struct grant_entry_v1);
+	else
 		gnttab_interface = &gnttab_v1_ops;
-	}
-	pr_info("Grant tables using version %d layout\n", grant_table_version);
+	pr_info("Grant tables using version %d layout\n",
+		gnttab_interface->version);
 }
 
 static int gnttab_setup(void)
@@ -1218,10 +1230,10 @@ static int gnttab_expand(unsigned int req_entries)
 	int rc;
 	unsigned int cur, extra;
 
-	BUG_ON(grefs_per_grant_frame == 0);
+	BUG_ON(gnttab_interface == NULL);
 	cur = nr_grant_frames;
-	extra = ((req_entries + (grefs_per_grant_frame-1)) /
-		 grefs_per_grant_frame);
+	extra = ((req_entries + gnttab_interface->grefs_per_grant_frame - 1) /
+		 gnttab_interface->grefs_per_grant_frame);
 	if (cur + extra > gnttab_max_grant_frames()) {
 		pr_warn_ratelimited("xen/grant-table: max_grant_frames reached"
 				    " cur=%u extra=%u limit=%u"
@@ -1253,16 +1265,16 @@ int gnttab_init(void)
 	/* Determine the maximum number of frames required for the
 	 * grant reference free list on the current hypervisor.
 	 */
-	BUG_ON(grefs_per_grant_frame == 0);
+	BUG_ON(gnttab_interface == NULL);
 	max_nr_glist_frames = (max_nr_grant_frames *
-			       grefs_per_grant_frame / RPP);
+			       gnttab_interface->grefs_per_grant_frame / RPP);
 
 	gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),
 			      GFP_KERNEL);
 	if (gnttab_list == NULL)
 		return -ENOMEM;
 
-	nr_glist_frames = (nr_grant_frames * grefs_per_grant_frame + RPP - 1) / RPP;
+	nr_glist_frames = gnttab_frames(nr_grant_frames, RPP);
 	for (i = 0; i < nr_glist_frames; i++) {
 		gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL);
 		if (gnttab_list[i] == NULL) {
@@ -1281,7 +1293,8 @@ int gnttab_init(void)
 		goto ini_nomem;
 	}
 
-	nr_init_grefs = nr_grant_frames * grefs_per_grant_frame;
+	nr_init_grefs = nr_grant_frames *
+			gnttab_interface->grefs_per_grant_frame;
 
 	for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++)
 		gnttab_entry(i) = i + 1;
-- 
2.12.3

[PATCH v2 4/5] xen: update arch/x86/include/asm/xen/cpuid.h

[Juergen Gross]

Update arch/x86/include/asm/xen/cpuid.h from the Xen tree to get newest
definitions.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/include/asm/xen/cpuid.h | 42 ++++++++++++++++++++++++++++++----------
 1 file changed, 32 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/xen/cpuid.h b/arch/x86/include/asm/xen/cpuid.h
index 3bdd10d71223..a9630104f1c4 100644
--- a/arch/x86/include/asm/xen/cpuid.h
+++ b/arch/x86/include/asm/xen/cpuid.h
@@ -74,21 +74,43 @@
 #define XEN_CPUID_FEAT1_MMU_PT_UPDATE_PRESERVE_AD  (1u<<0)
 
 /*
+ * Leaf 4 (0x40000x03)
+ * Sub-leaf 0: EAX: bit 0: emulated tsc
+ *                  bit 1: host tsc is known to be reliable
+ *                  bit 2: RDTSCP instruction available
+ *             EBX: tsc_mode: 0=default (emulate if necessary), 1=emulate,
+ *                            2=no emulation, 3=no emulation + TSC_AUX support
+ *             ECX: guest tsc frequency in kHz
+ *             EDX: guest tsc incarnation (migration count)
+ * Sub-leaf 1: EAX: tsc offset low part
+ *             EBX: tsc offset high part
+ *             ECX: multiplicator for tsc->ns conversion
+ *             EDX: shift amount for tsc->ns conversion
+ * Sub-leaf 2: EAX: host tsc frequency in kHz
+ */
+
+/*
  * Leaf 5 (0x40000x04)
  * HVM-specific features
- * EAX: Features
- * EBX: vcpu id (iff EAX has XEN_HVM_CPUID_VCPU_ID_PRESENT flag)
+ * Sub-leaf 0: EAX: Features
+ * Sub-leaf 0: EBX: vcpu id (iff EAX has XEN_HVM_CPUID_VCPU_ID_PRESENT flag)
  */
-
-/* Virtualized APIC registers */
-#define XEN_HVM_CPUID_APIC_ACCESS_VIRT (1u << 0)
-/* Virtualized x2APIC accesses */
-#define XEN_HVM_CPUID_X2APIC_VIRT      (1u << 1)
+#define XEN_HVM_CPUID_APIC_ACCESS_VIRT (1u << 0) /* Virtualized APIC registers */
+#define XEN_HVM_CPUID_X2APIC_VIRT      (1u << 1) /* Virtualized x2APIC accesses */
 /* Memory mapped from other domains has valid IOMMU entries */
 #define XEN_HVM_CPUID_IOMMU_MAPPINGS   (1u << 2)
-/* vcpu id is present in EBX */
-#define XEN_HVM_CPUID_VCPU_ID_PRESENT  (1u << 3)
+#define XEN_HVM_CPUID_VCPU_ID_PRESENT  (1u << 3) /* vcpu id is present in EBX */
+
+/*
+ * Leaf 6 (0x40000x05)
+ * PV-specific parameters
+ * Sub-leaf 0: EAX: max available sub-leaf
+ * Sub-leaf 0: EBX: bits 0-7: max machine address width
+ */
+
+/* Max. address width in bits taking memory hotplug into account. */
+#define XEN_CPUID_MACHINE_ADDRESS_WIDTH_MASK (0xffu << 0)
 
-#define XEN_CPUID_MAX_NUM_LEAVES 4
+#define XEN_CPUID_MAX_NUM_LEAVES 5
 
 #endif /* __XEN_PUBLIC_ARCH_X86_CPUID_H__ */
-- 
2.12.3

[PATCH v2 5/5] xen: select grant interface version

[Juergen Gross]

Grant v2 will be needed in cases where a frame number in the grant
table can exceed 32 bits. For PV guests this is a host feature, while
for HVM guests this is a guest feature.

So select grant v2 in case frame numbers can be larger than 32 bits
and grant v1 else.

For testing purposes add a way to specify the grant interface version
via a boot parameter.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2:
- use cpuid on pv and max_possible_pfn on hvm for version select
---
 drivers/xen/grant-table.c | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 573e7fe9b147..fa152832e0e6 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -33,6 +33,7 @@
 
 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
 
+#include <linux/bootmem.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
@@ -43,6 +44,7 @@
 #include <linux/hardirq.h>
 #include <linux/workqueue.h>
 #include <linux/ratelimit.h>
+#include <linux/moduleparam.h>
 
 #include <xen/xen.h>
 #include <xen/interface/xen.h>
@@ -52,6 +54,9 @@
 #include <xen/hvc-console.h>
 #include <xen/swiotlb-xen.h>
 #include <xen/balloon.h>
+#ifdef CONFIG_X86
+#include <asm/xen/cpuid.h>
+#endif
 #include <asm/xen/hypercall.h>
 #include <asm/xen/interface.h>
 
@@ -68,6 +73,8 @@ static int gnttab_free_count;
 static grant_ref_t gnttab_free_head;
 static DEFINE_SPINLOCK(gnttab_list_lock);
 struct grant_frames xen_auto_xlat_grant_frames;
+static unsigned int xen_gnttab_version;
+module_param_named(version, xen_gnttab_version, uint, 0);
 
 static union {
 	struct grant_entry_v1 *v1;
@@ -1177,12 +1184,36 @@ static const struct gnttab_ops gnttab_v2_ops = {
 	.query_foreign_access		= gnttab_query_foreign_access_v2,
 };
 
+static bool gnttab_need_v2(void)
+{
+#ifdef CONFIG_X86
+	uint32_t base, width;
+
+	if (xen_pv_domain()) {
+		base = xen_cpuid_base();
+		if (cpuid_eax(base) < 5)
+			return false;	/* Information not available, use V1. */
+		width = cpuid_ebx(base + 5) &
+			XEN_CPUID_MACHINE_ADDRESS_WIDTH_MASK;
+		return width > 32 + PAGE_SHIFT;
+	}
+#endif
+	return !!(max_possible_pfn >> 32);
+}
+
 static void gnttab_request_version(void)
 {
-	int rc;
+	long rc;
 	struct gnttab_set_version gsv;
 
-	gsv.version = 1;
+	if (gnttab_need_v2())
+		gsv.version = 2;
+	else
+		gsv.version = 1;
+
+	/* Boot parameter overrides automatic selection. */
+	if (xen_gnttab_version >= 1 && xen_gnttab_version <= 2)
+		gsv.version = xen_gnttab_version;
 
 	rc = HYPERVISOR_grant_table_op(GNTTABOP_set_version, &gsv, 1);
 	if (rc == 0 && gsv.version == 2)
-- 
2.12.3

Re: [PATCH v2 0/5] xen: grant table interface v2 support

[Boris Ostrovsky]

On 11/02/2017 05:19 AM, Juergen Gross wrote:
> In order to support Linux to run as a pv guest on machines with huge
> memory (>16TB) or as a hvm guest with more than 16TB of memory the
> kernel has to support grant table interface v2, as v1 is limited to
> 32 bit frame numbers.
>
> This series re-adds that support (it has been removed in 2015) and
> restricts usage of v2 to the features of v1 in order to support
> migration to hosts which only support v1.
>
> V2 is selected only in the following cases:
> - the user has specified v2 via module parameter
> - in a pv guest if the maximum possible memory address of the host is
>   above 16TB (memory hotplug taken into account)
> - in a hvm guest if the maximum guest memory address is above 16TB
>   (again with memory hotplug taken into account)
>
> Changes in V2:
> - patch 2: remove update_trans_entry() from gnttab_ops (Boris Ostrovsky)
> - added new patch 4
> - patch 5: use cpuid on pv and max_possible_pfn on hvm for version select
>
> Juergen Gross (5):
>   xen: re-introduce support for grant v2 interface
>   xen: limit grant v2 interface to the v1 functionality
>   xen: add grant interface version dependent constants to gnttab_ops
>   xen: update arch/x86/include/asm/xen/cpuid.h
>   xen: select grant interface version
>
>  arch/arm/xen/grant-table.c       |   9 +-
>  arch/x86/include/asm/xen/cpuid.h |  42 +++++--
>  arch/x86/xen/grant-table.c       |  60 +++++++++-
>  drivers/xen/grant-table.c        | 244 +++++++++++++++++++++++++++++++++++----
>  include/xen/grant_table.h        |   5 +-
>  5 files changed, 318 insertions(+), 42 deletions(-)
>


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

Re: [PATCH v2 0/5] xen: grant table interface v2 support

[Boris Ostrovsky]

On 11/06/2017 03:46 PM, Boris Ostrovsky wrote:
> On 11/02/2017 05:19 AM, Juergen Gross wrote:
>> In order to support Linux to run as a pv guest on machines with huge
>> memory (>16TB) or as a hvm guest with more than 16TB of memory the
>> kernel has to support grant table interface v2, as v1 is limited to
>> 32 bit frame numbers.
>>
>> This series re-adds that support (it has been removed in 2015) and
>> restricts usage of v2 to the features of v1 in order to support
>> migration to hosts which only support v1.
>>
>> V2 is selected only in the following cases:
>> - the user has specified v2 via module parameter
>> - in a pv guest if the maximum possible memory address of the host is
>>   above 16TB (memory hotplug taken into account)
>> - in a hvm guest if the maximum guest memory address is above 16TB
>>   (again with memory hotplug taken into account)
>>
>> Changes in V2:
>> - patch 2: remove update_trans_entry() from gnttab_ops (Boris Ostrovsky)
>> - added new patch 4
>> - patch 5: use cpuid on pv and max_possible_pfn on hvm for version select
>>
>> Juergen Gross (5):
>>   xen: re-introduce support for grant v2 interface
>>   xen: limit grant v2 interface to the v1 functionality
>>   xen: add grant interface version dependent constants to gnttab_ops
>>   xen: update arch/x86/include/asm/xen/cpuid.h
>>   xen: select grant interface version
>>
>>  arch/arm/xen/grant-table.c       |   9 +-
>>  arch/x86/include/asm/xen/cpuid.h |  42 +++++--
>>  arch/x86/xen/grant-table.c       |  60 +++++++++-
>>  drivers/xen/grant-table.c        | 244 +++++++++++++++++++++++++++++++++++----
>>  include/xen/grant_table.h        |   5 +-
>>  5 files changed, 318 insertions(+), 42 deletions(-)
>>
>
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>


Applied to for-linus-4.15.

-boris