Merge tag 'for-linus-6.10a-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from Juergen Gross:

 - a small cleanup in the drivers/xen/xenbus Makefile

 - a fix of the Xen xenstore driver to improve connecting to a late
   started Xenstore

 - an enhancement for better support of ballooning in PVH guests

 - a cleanup using try_cmpxchg() instead of open coding it

* tag 'for-linus-6.10a-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  drivers/xen: Improve the late XenStore init protocol
  xen/xenbus: Use *-y instead of *-objs in Makefile
  xen/x86: add extra pages to unpopulated-alloc if available
  locking/x86/xen: Use try_cmpxchg() in xen_alloc_p2m_entry()

4 files changed, 67 insertions, 27 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 5f3a69f6ec34..0305485edcd3 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -379,3 +379,36 @@ void __init xen_add_extra_mem(unsigned long start_pfn, unsigned long n_pfns)
 
 	memblock_reserve(PFN_PHYS(start_pfn), PFN_PHYS(n_pfns));
 }
+
+#ifdef CONFIG_XEN_UNPOPULATED_ALLOC
+int __init arch_xen_unpopulated_init(struct resource **res)
+{
+	unsigned int i;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	/* Must be set strictly before calling xen_free_unpopulated_pages(). */
+	*res = &iomem_resource;
+
+	/*
+	 * Initialize with pages from the extra memory regions (see
+	 * arch/x86/xen/setup.c).
+	 */
+	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
+		unsigned int j;
+
+		for (j = 0; j < xen_extra_mem[i].n_pfns; j++) {
+			struct page *pg =
+				pfn_to_page(xen_extra_mem[i].start_pfn + j);
+
+			xen_free_unpopulated_pages(1, &pg);
+		}
+
+		/* Zero so region is not also added to the balloon driver. */
+		xen_extra_mem[i].n_pfns = 0;
+	}
+
+	return 0;
+}
+#endif
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 9bdc3b656b2c..99918beccd80 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -555,7 +555,6 @@ int xen_alloc_p2m_entry(unsigned long pfn)
 			/* Separately check the mid mfn level */
 			unsigned long missing_mfn;
 			unsigned long mid_mfn_mfn;
-			unsigned long old_mfn;
 
 			mid_mfn = alloc_p2m_page();
 			if (!mid_mfn)
@@ -565,12 +564,12 @@ int xen_alloc_p2m_entry(unsigned long pfn)
 
 			missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
 			mid_mfn_mfn = virt_to_mfn(mid_mfn);
-			old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
-			if (old_mfn != missing_mfn) {
-				free_p2m_page(mid_mfn);
-				mid_mfn = mfn_to_virt(old_mfn);
-			} else {
+			/* try_cmpxchg() updates missing_mfn on failure. */
+			if (try_cmpxchg(top_mfn_p, &missing_mfn, mid_mfn_mfn)) {
 				p2m_top_mfn_p[topidx] = mid_mfn;
+			} else {
+				free_p2m_page(mid_mfn);
+				mid_mfn = mfn_to_virt(missing_mfn);
 			}
 		}
 	} else {
diff --git a/drivers/xen/xenbus/Makefile b/drivers/xen/xenbus/Makefile
index 0c7532110815..b0d69602214e 100644
--- a/drivers/xen/xenbus/Makefile
+++ b/drivers/xen/xenbus/Makefile
@@ -1,15 +1,13 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-y	+= xenbus.o
-obj-y	+= xenbus_dev_frontend.o
 
-xenbus-objs =
-xenbus-objs += xenbus_client.o
-xenbus-objs += xenbus_comms.o
-xenbus-objs += xenbus_xs.o
-xenbus-objs += xenbus_probe.o
+xenbus-y := xenbus_client.o
+xenbus-y += xenbus_comms.o
+xenbus-y += xenbus_xs.o
+xenbus-y += xenbus_probe.o
 
-xenbus-be-objs-$(CONFIG_XEN_BACKEND) += xenbus_probe_backend.o
-xenbus-objs += $(xenbus-be-objs-y)
+xenbus-$(CONFIG_XEN_BACKEND) += xenbus_probe_backend.o
 
+obj-y	+= xenbus_dev_frontend.o
 obj-$(CONFIG_XEN_BACKEND) += xenbus_dev_backend.o
 obj-$(CONFIG_XEN_XENBUS_FRONTEND) += xenbus_probe_frontend.o
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 3205e5d724c8..1a9ded0cddcb 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -65,13 +65,17 @@
 #include "xenbus.h"
 
 
-static int xs_init_irq;
+static int xs_init_irq = -1;
 int xen_store_evtchn;
 EXPORT_SYMBOL_GPL(xen_store_evtchn);
 
 struct xenstore_domain_interface *xen_store_interface;
 EXPORT_SYMBOL_GPL(xen_store_interface);
 
+#define XS_INTERFACE_READY \
+	((xen_store_interface != NULL) && \
+	 (xen_store_interface->connection == XENSTORE_CONNECTED))
+
 enum xenstore_init xen_store_domain_type;
 EXPORT_SYMBOL_GPL(xen_store_domain_type);
 
@@ -751,19 +755,19 @@ static void xenbus_probe(void)
 {
 	xenstored_ready = 1;
 
-	if (!xen_store_interface) {
+	if (!xen_store_interface)
 		xen_store_interface = memremap(xen_store_gfn << XEN_PAGE_SHIFT,
 					       XEN_PAGE_SIZE, MEMREMAP_WB);
-		/*
-		 * Now it is safe to free the IRQ used for xenstore late
-		 * initialization. No need to unbind: it is about to be
-		 * bound again from xb_init_comms. Note that calling
-		 * unbind_from_irqhandler now would result in xen_evtchn_close()
-		 * being called and the event channel not being enabled again
-		 * afterwards, resulting in missed event notifications.
-		 */
+	/*
+	 * Now it is safe to free the IRQ used for xenstore late
+	 * initialization. No need to unbind: it is about to be
+	 * bound again from xb_init_comms. Note that calling
+	 * unbind_from_irqhandler now would result in xen_evtchn_close()
+	 * being called and the event channel not being enabled again
+	 * afterwards, resulting in missed event notifications.
+	 */
+	if (xs_init_irq >= 0)
 		free_irq(xs_init_irq, &xb_waitq);
-	}
 
 	/*
 	 * In the HVM case, xenbus_init() deferred its call to
@@ -822,7 +826,7 @@ static int __init xenbus_probe_initcall(void)
 	if (xen_store_domain_type == XS_PV ||
 	    (xen_store_domain_type == XS_HVM &&
 	     !xs_hvm_defer_init_for_callback() &&
-	     xen_store_interface != NULL))
+	     XS_INTERFACE_READY))
 		xenbus_probe();
 
 	/*
@@ -831,7 +835,7 @@ static int __init xenbus_probe_initcall(void)
 	 * started, then probe.  It will be triggered when communication
 	 * starts happening, by waiting on xb_waitq.
 	 */
-	if (xen_store_domain_type == XS_LOCAL || xen_store_interface == NULL) {
+	if (xen_store_domain_type == XS_LOCAL || !XS_INTERFACE_READY) {
 		struct task_struct *probe_task;
 
 		probe_task = kthread_run(xenbus_probe_thread, NULL,
@@ -1014,6 +1018,12 @@ static int __init xenbus_init(void)
 			xen_store_interface =
 				memremap(xen_store_gfn << XEN_PAGE_SHIFT,
 					 XEN_PAGE_SIZE, MEMREMAP_WB);
+			if (!xen_store_interface) {
+				pr_err("%s: cannot map HVM_PARAM_STORE_PFN=%llx\n",
+				       __func__, v);
+				err = -EINVAL;
+				goto out_error;
+			}
 			if (xen_store_interface->connection != XENSTORE_CONNECTED)
 				wait = true;
 		}