xen/balloon: Share common memory reservation routines

Memory {increase|decrease}_reservation and VA mappings update/reset
code used in balloon driver can be made common, so other drivers can
also re-use the same functionality without open-coding.
Create a dedicated file for the shared code and export corresponding
symbols for other kernel modules.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

4 files changed, 184 insertions, 69 deletions

diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
index 48b154276179..129dd1cc1b83 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -2,6 +2,7 @@
 obj-$(CONFIG_HOTPLUG_CPU)               += cpu_hotplug.o
 obj-$(CONFIG_X86)                       += fallback.o
 obj-y   += grant-table.o features.o balloon.o manage.o preempt.o time.o
+obj-y   += mem-reservation.o
 obj-y   += events/
 obj-y   += xenbus/
 
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 065f0b607373..e12bb256036f 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -71,6 +71,7 @@
 #include <xen/balloon.h>
 #include <xen/features.h>
 #include <xen/page.h>
+#include <xen/mem-reservation.h>
 
 static int xen_hotplug_unpopulated;
 
@@ -157,13 +158,6 @@ static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
 #define GFP_BALLOON \
         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
 
-static void scrub_page(struct page *page)
-{
-#ifdef CONFIG_XEN_SCRUB_PAGES
-        clear_highpage(page);
-#endif
-}
-
 /* balloon_append: add the given page to the balloon. */
 static void __balloon_append(struct page *page)
 {
@@ -463,11 +457,6 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
         int rc;
         unsigned long i;
         struct page   *page;
-        struct xen_memory_reservation reservation = {
-                .address_bits = 0,
-                .extent_order = EXTENT_ORDER,
-                .domid        = DOMID_SELF
-        };
 
         if (nr_pages > ARRAY_SIZE(frame_list))
                 nr_pages = ARRAY_SIZE(frame_list);
@@ -479,16 +468,11 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
                         break;
                 }
 
-                /* XENMEM_populate_physmap requires a PFN based on Xen
-                 * granularity.
-                 */
                 frame_list[i] = page_to_xen_pfn(page);
                 page = balloon_next_page(page);
         }
 
-        set_xen_guest_handle(reservation.extent_start, frame_list);
-        reservation.nr_extents = nr_pages;
-        rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
+        rc = xenmem_reservation_increase(nr_pages, frame_list);
         if (rc <= 0)
                 return BP_EAGAIN;
 
@@ -496,29 +480,7 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
                 page = balloon_retrieve(false);
                 BUG_ON(page == NULL);
 
-#ifdef CONFIG_XEN_HAVE_PVMMU
-                /*
-                 * We don't support PV MMU when Linux and Xen is using
-                 * different page granularity.
-                 */
-                BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
-
-                if (!xen_feature(XENFEAT_auto_translated_physmap)) {
-                        unsigned long pfn = page_to_pfn(page);
-
-                        set_phys_to_machine(pfn, frame_list[i]);
-
-                        /* Link back into the page tables if not highmem. */
-                        if (!PageHighMem(page)) {
-                                int ret;
-                                ret = HYPERVISOR_update_va_mapping(
-                                                (unsigned long)__va(pfn << PAGE_SHIFT),
-                                                mfn_pte(frame_list[i], PAGE_KERNEL),
-                                                0);
-                                BUG_ON(ret);
-                        }
-                }
-#endif
+                xenmem_reservation_va_mapping_update(1, &page, &frame_list[i]);
 
                 /* Relinquish the page back to the allocator. */
                 free_reserved_page(page);
@@ -535,11 +497,6 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
         unsigned long i;
         struct page *page, *tmp;
         int ret;
-        struct xen_memory_reservation reservation = {
-                .address_bits = 0,
-                .extent_order = EXTENT_ORDER,
-                .domid        = DOMID_SELF
-        };
         LIST_HEAD(pages);
 
         if (nr_pages > ARRAY_SIZE(frame_list))
@@ -553,7 +510,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
                         break;
                 }
                 adjust_managed_page_count(page, -1);
-                scrub_page(page);
+                xenmem_reservation_scrub_page(page);
                 list_add(&page->lru, &pages);
         }
 
@@ -572,28 +529,10 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
          */
         i = 0;
         list_for_each_entry_safe(page, tmp, &pages, lru) {
-                /* XENMEM_decrease_reservation requires a GFN */
                 frame_list[i++] = xen_page_to_gfn(page);
 
-#ifdef CONFIG_XEN_HAVE_PVMMU
-                /*
-                 * We don't support PV MMU when Linux and Xen is using
-                 * different page granularity.
-                 */
-                BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
-
-                if (!xen_feature(XENFEAT_auto_translated_physmap)) {
-                        unsigned long pfn = page_to_pfn(page);
+                xenmem_reservation_va_mapping_reset(1, &page);
 
-                        if (!PageHighMem(page)) {
-                                ret = HYPERVISOR_update_va_mapping(
-                                                (unsigned long)__va(pfn << PAGE_SHIFT),
-                                                __pte_ma(0), 0);
-                                BUG_ON(ret);
-                        }
-                        __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
-                }
-#endif
                 list_del(&page->lru);
 
                 balloon_append(page);
@@ -601,9 +540,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 
         flush_tlb_all();
 
-        set_xen_guest_handle(reservation.extent_start, frame_list);
-        reservation.nr_extents   = nr_pages;
-        ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+        ret = xenmem_reservation_decrease(nr_pages, frame_list);
         BUG_ON(ret != nr_pages);
 
         balloon_stats.current_pages -= nr_pages;
diff --git a/drivers/xen/mem-reservation.c b/drivers/xen/mem-reservation.c
new file mode 100644
index 000000000000..084799c6180e
--- /dev/null
+++ b/drivers/xen/mem-reservation.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/******************************************************************************
+ * Xen memory reservation utilities.
+ *
+ * Copyright (c) 2003, B Dragovic
+ * Copyright (c) 2003-2004, M Williamson, K Fraser
+ * Copyright (c) 2005 Dan M. Smith, IBM Corporation
+ * Copyright (c) 2010 Daniel Kiper
+ * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
+ */
+
+#include <asm/xen/hypercall.h>
+
+#include <xen/interface/memory.h>
+#include <xen/mem-reservation.h>
+
+/*
+ * Use one extent per PAGE_SIZE to avoid to break down the page into
+ * multiple frame.
+ */
+#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
+
+#ifdef CONFIG_XEN_HAVE_PVMMU
+void __xenmem_reservation_va_mapping_update(unsigned long count,
+                                            struct page **pages,
+                                            xen_pfn_t *frames)
+{
+        int i;
+
+        for (i = 0; i < count; i++) {
+                struct page *page = pages[i];
+                unsigned long pfn = page_to_pfn(page);
+
+                BUG_ON(!page);
+
+                /*
+                 * We don't support PV MMU when Linux and Xen is using
+                 * different page granularity.
+                 */
+                BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
+                set_phys_to_machine(pfn, frames[i]);
+
+                /* Link back into the page tables if not highmem. */
+                if (!PageHighMem(page)) {
+                        int ret;
+
+                        ret = HYPERVISOR_update_va_mapping(
+                                        (unsigned long)__va(pfn << PAGE_SHIFT),
+                                        mfn_pte(frames[i], PAGE_KERNEL),
+                                        0);
+                        BUG_ON(ret);
+                }
+        }
+}
+EXPORT_SYMBOL_GPL(__xenmem_reservation_va_mapping_update);
+
+void __xenmem_reservation_va_mapping_reset(unsigned long count,
+                                           struct page **pages)
+{
+        int i;
+
+        for (i = 0; i < count; i++) {
+                struct page *page = pages[i];
+                unsigned long pfn = page_to_pfn(page);
+
+                /*
+                 * We don't support PV MMU when Linux and Xen are using
+                 * different page granularity.
+                 */
+                BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
+                if (!PageHighMem(page)) {
+                        int ret;
+
+                        ret = HYPERVISOR_update_va_mapping(
+                                        (unsigned long)__va(pfn << PAGE_SHIFT),
+                                        __pte_ma(0), 0);
+                        BUG_ON(ret);
+                }
+                __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
+        }
+}
+EXPORT_SYMBOL_GPL(__xenmem_reservation_va_mapping_reset);
+#endif /* CONFIG_XEN_HAVE_PVMMU */
+
+/* @frames is an array of PFNs */
+int xenmem_reservation_increase(int count, xen_pfn_t *frames)
+{
+        struct xen_memory_reservation reservation = {
+                .address_bits = 0,
+                .extent_order = EXTENT_ORDER,
+                .domid        = DOMID_SELF
+        };
+
+        /* XENMEM_populate_physmap requires a PFN based on Xen granularity. */
+        set_xen_guest_handle(reservation.extent_start, frames);
+        reservation.nr_extents = count;
+        return HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
+}
+EXPORT_SYMBOL_GPL(xenmem_reservation_increase);
+
+/* @frames is an array of GFNs */
+int xenmem_reservation_decrease(int count, xen_pfn_t *frames)
+{
+        struct xen_memory_reservation reservation = {
+                .address_bits = 0,
+                .extent_order = EXTENT_ORDER,
+                .domid        = DOMID_SELF
+        };
+
+        /* XENMEM_decrease_reservation requires a GFN */
+        set_xen_guest_handle(reservation.extent_start, frames);
+        reservation.nr_extents = count;
+        return HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+}
+EXPORT_SYMBOL_GPL(xenmem_reservation_decrease);
diff --git a/include/xen/mem-reservation.h b/include/xen/mem-reservation.h
new file mode 100644
index 000000000000..80b52b4945e9
--- /dev/null
+++ b/include/xen/mem-reservation.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Xen memory reservation utilities.
+ *
+ * Copyright (c) 2003, B Dragovic
+ * Copyright (c) 2003-2004, M Williamson, K Fraser
+ * Copyright (c) 2005 Dan M. Smith, IBM Corporation
+ * Copyright (c) 2010 Daniel Kiper
+ * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
+ */
+
+#ifndef _XENMEM_RESERVATION_H
+#define _XENMEM_RESERVATION_H
+
+#include <linux/highmem.h>
+
+#include <xen/page.h>
+
+static inline void xenmem_reservation_scrub_page(struct page *page)
+{
+#ifdef CONFIG_XEN_SCRUB_PAGES
+        clear_highpage(page);
+#endif
+}
+
+#ifdef CONFIG_XEN_HAVE_PVMMU
+void __xenmem_reservation_va_mapping_update(unsigned long count,
+                                            struct page **pages,
+                                            xen_pfn_t *frames);
+
+void __xenmem_reservation_va_mapping_reset(unsigned long count,
+                                           struct page **pages);
+#endif
+
+static inline void xenmem_reservation_va_mapping_update(unsigned long count,
+                                                        struct page **pages,
+                                                        xen_pfn_t *frames)
+{
+#ifdef CONFIG_XEN_HAVE_PVMMU
+        if (!xen_feature(XENFEAT_auto_translated_physmap))
+                __xenmem_reservation_va_mapping_update(count, pages, frames);
+#endif
+}
+
+static inline void xenmem_reservation_va_mapping_reset(unsigned long count,
+                                                       struct page **pages)
+{
+#ifdef CONFIG_XEN_HAVE_PVMMU
+        if (!xen_feature(XENFEAT_auto_translated_physmap))
+                __xenmem_reservation_va_mapping_reset(count, pages);
+#endif
+}
+
+int xenmem_reservation_increase(int count, xen_pfn_t *frames);
+
+int xenmem_reservation_decrease(int count, xen_pfn_t *frames);
+
+#endif