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

3 files changed, 23 insertions, 40 deletions

diff --git a/drivers/xen/features.c b/drivers/xen/features.c
index 25c053b09605..7b591443833c 100644
--- a/drivers/xen/features.c
+++ b/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);
+	}
 }
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index a3e7be96527d..1e7f6b1c0c97 100644
--- a/drivers/xen/gntdev.c
+++ b/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;
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index 0cd728961fce..e8bed1cb76ba 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/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;