xen: fixes for 4.20-rc2

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Merge tag 'for-linus-4.20a-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen fixes from Juergen Gross:
 "Several fixes, mostly for rather recent regressions when running under
  Xen"

* tag 'for-linus-4.20a-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen: remove size limit of privcmd-buf mapping interface
  xen: fix xen_qlock_wait()
  x86/xen: fix pv boot
  xen-blkfront: fix kernel panic with negotiate_mq error path
  xen/grant-table: Fix incorrect gnttab_dma_free_pages() pr_debug message
  CONFIG_XEN_PV breaks xen_create_contiguous_region on ARM

arch/x86/include/asm/xen/page.h

@@ -9,7 +9,7 @@
 #include <linux/mm.h>
 #include <linux/device.h>
 
-#include <linux/uaccess.h>
+#include <asm/extable.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>
 
@@ -93,12 +93,39 @@ clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
  */
 static inline int xen_safe_write_ulong(unsigned long *addr, unsigned long val)
 {
-	return __put_user(val, (unsigned long __user *)addr);
+	int ret = 0;
+
+	asm volatile("1: mov %[val], %[ptr]\n"
+		     "2:\n"
+		     ".section .fixup, \"ax\"\n"
+		     "3: sub $1, %[ret]\n"
+		     "   jmp 2b\n"
+		     ".previous\n"
+		     _ASM_EXTABLE(1b, 3b)
+		     : [ret] "+r" (ret), [ptr] "=m" (*addr)
+		     : [val] "r" (val));
+
+	return ret;
 }
 
-static inline int xen_safe_read_ulong(unsigned long *addr, unsigned long *val)
+static inline int xen_safe_read_ulong(const unsigned long *addr,
+				      unsigned long *val)
 {
-	return __get_user(*val, (unsigned long __user *)addr);
+	int ret = 0;
+	unsigned long rval = ~0ul;
+
+	asm volatile("1: mov %[ptr], %[rval]\n"
+		     "2:\n"
+		     ".section .fixup, \"ax\"\n"
+		     "3: sub $1, %[ret]\n"
+		     "   jmp 2b\n"
+		     ".previous\n"
+		     _ASM_EXTABLE(1b, 3b)
+		     : [ret] "+r" (ret), [rval] "+r" (rval)
+		     : [ptr] "m" (*addr));
+	*val = rval;
+
+	return ret;
 }
 
 #ifdef CONFIG_XEN_PV

arch/x86/xen/p2m.c

@@ -656,8 +656,7 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 
 	/*
 	 * The interface requires atomic updates on p2m elements.
-	 * xen_safe_write_ulong() is using __put_user which does an atomic
-	 * store via asm().
+	 * xen_safe_write_ulong() is using an atomic store via asm().
 	 */
 	if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
 		return true;

arch/x86/xen/spinlock.c

@@ -9,6 +9,7 @@
 #include <linux/log2.h>
 #include <linux/gfp.h>
 #include <linux/slab.h>
+#include <linux/atomic.h>
 
 #include <asm/paravirt.h>
 #include <asm/qspinlock.h>
@@ -21,6 +22,7 @@
 
 static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
 static DEFINE_PER_CPU(char *, irq_name);
+static DEFINE_PER_CPU(atomic_t, xen_qlock_wait_nest);
 static bool xen_pvspin = true;
 
 static void xen_qlock_kick(int cpu)
@@ -39,25 +41,25 @@ static void xen_qlock_kick(int cpu)
  */
 static void xen_qlock_wait(u8 *byte, u8 val)
 {
-	unsigned long flags;
 	int irq = __this_cpu_read(lock_kicker_irq);
+	atomic_t *nest_cnt = this_cpu_ptr(&xen_qlock_wait_nest);
 
 	/* If kicker interrupts not initialized yet, just spin */
 	if (irq == -1 || in_nmi())
 		return;
 
-	/* Guard against reentry. */
-	local_irq_save(flags);
+	/* Detect reentry. */
+	atomic_inc(nest_cnt);
 
-	/* If irq pending already clear it. */
-	if (xen_test_irq_pending(irq)) {
+	/* If irq pending already and no nested call clear it. */
+	if (atomic_read(nest_cnt) == 1 && xen_test_irq_pending(irq)) {
 		xen_clear_irq_pending(irq);
 	} else if (READ_ONCE(*byte) == val) {
 		/* Block until irq becomes pending (or a spurious wakeup) */
 		xen_poll_irq(irq);
 	}
 
-	local_irq_restore(flags);
+	atomic_dec(nest_cnt);
 }
 
 static irqreturn_t dummy_handler(int irq, void *dev_id)

drivers/block/xen-blkfront.c

@@ -1919,6 +1919,7 @@ static int negotiate_mq(struct blkfront_info *info)
 			      GFP_KERNEL);
 	if (!info->rinfo) {
 		xenbus_dev_fatal(info->xbdev, -ENOMEM, "allocating ring_info structure");
+		info->nr_rings = 0;
 		return -ENOMEM;
 	}
 

drivers/xen/grant-table.c

@@ -914,7 +914,7 @@ int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args)
 
 	ret = xenmem_reservation_increase(args->nr_pages, args->frames);
 	if (ret != args->nr_pages) {
-		pr_debug("Failed to decrease reservation for DMA buffer\n");
+		pr_debug("Failed to increase reservation for DMA buffer\n");
 		ret = -EFAULT;
 	} else {
 		ret = 0;

drivers/xen/privcmd-buf.c

@@ -21,15 +21,9 @@
 
 MODULE_LICENSE("GPL");
 
-static unsigned int limit = 64;
-module_param(limit, uint, 0644);
-MODULE_PARM_DESC(limit, "Maximum number of pages that may be allocated by "
-			"the privcmd-buf device per open file");
-
 struct privcmd_buf_private {
 	struct mutex lock;
 	struct list_head list;
-	unsigned int allocated;
 };
 
 struct privcmd_buf_vma_private {
@@ -60,12 +54,9 @@ static void privcmd_buf_vmapriv_free(struct privcmd_buf_vma_private *vma_priv)
 {
 	unsigned int i;
 
-	vma_priv->file_priv->allocated -= vma_priv->n_pages;
-
 	list_del(&vma_priv->list);
 
 	for (i = 0; i < vma_priv->n_pages; i++)
-		if (vma_priv->pages[i])
 		__free_page(vma_priv->pages[i]);
 
 	kfree(vma_priv);
@@ -146,8 +137,7 @@ static int privcmd_buf_mmap(struct file *file, struct vm_area_struct *vma)
 	unsigned int i;
 	int ret = 0;
 
-	if (!(vma->vm_flags & VM_SHARED) || count > limit ||
-	    file_priv->allocated + count > limit)
+	if (!(vma->vm_flags & VM_SHARED))
 		return -EINVAL;
 
 	vma_priv = kzalloc(sizeof(*vma_priv) + count * sizeof(void *),
@@ -155,19 +145,15 @@ static int privcmd_buf_mmap(struct file *file, struct vm_area_struct *vma)
 	if (!vma_priv)
 		return -ENOMEM;
 
-	vma_priv->n_pages = count;
-	count = 0;
-	for (i = 0; i < vma_priv->n_pages; i++) {
+	for (i = 0; i < count; i++) {
 		vma_priv->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO);
 		if (!vma_priv->pages[i])
 			break;
-		count++;
+		vma_priv->n_pages++;
 	}
 
 	mutex_lock(&file_priv->lock);
 
-	file_priv->allocated += count;
-
 	vma_priv->file_priv = file_priv;
 	vma_priv->users = 1;
 

include/xen/xen-ops.h

@@ -42,16 +42,12 @@ int xen_setup_shutdown_event(void);
 
 extern unsigned long *xen_contiguous_bitmap;
 
-#ifdef CONFIG_XEN_PV
+#if defined(CONFIG_XEN_PV) || defined(CONFIG_ARM) || defined(CONFIG_ARM64)
 int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
 				unsigned int address_bits,
 				dma_addr_t *dma_handle);
 
 void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order);
-
-int xen_remap_pfn(struct vm_area_struct *vma, unsigned long addr,
-		  xen_pfn_t *pfn, int nr, int *err_ptr, pgprot_t prot,
-		  unsigned int domid, bool no_translate, struct page **pages);
 #else
 static inline int xen_create_contiguous_region(phys_addr_t pstart,
 					       unsigned int order,
@@ -63,7 +59,13 @@ static inline int xen_create_contiguous_region(phys_addr_t pstart,
 
 static inline void xen_destroy_contiguous_region(phys_addr_t pstart,
 						 unsigned int order) { }
+#endif
 
+#if defined(CONFIG_XEN_PV)
+int xen_remap_pfn(struct vm_area_struct *vma, unsigned long addr,
+		  xen_pfn_t *pfn, int nr, int *err_ptr, pgprot_t prot,
+		  unsigned int domid, bool no_translate, struct page **pages);
+#else
 static inline int xen_remap_pfn(struct vm_area_struct *vma, unsigned long addr,
 				xen_pfn_t *pfn, int nr, int *err_ptr,
 				pgprot_t prot,  unsigned int domid,