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[Xen-devel] [PATCH v5 2/8] xen/balloon: Share common memory reservation routines



From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

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@xxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
 drivers/xen/Makefile          |   1 +
 drivers/xen/balloon.c         |  75 ++-------------------
 drivers/xen/mem-reservation.c | 118 ++++++++++++++++++++++++++++++++++
 include/xen/mem-reservation.h |  59 +++++++++++++++++
 4 files changed, 184 insertions(+), 69 deletions(-)
 create mode 100644 drivers/xen/mem-reservation.c
 create mode 100644 include/xen/mem-reservation.h

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
-- 
2.18.0


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