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Re: [Xen-devel] [PATCH 2/8] xen/balloon: Move common memory reservation routines to a module



On 05/30/2018 07:32 AM, Juergen Gross wrote:
On 25/05/18 17:33, Oleksandr Andrushchenko wrote:
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 module for the shared code and export corresponding
symbols for other kernel modules.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
---
  drivers/xen/Makefile          |   1 +
  drivers/xen/balloon.c         |  71 ++----------------
  drivers/xen/mem-reservation.c | 134 ++++++++++++++++++++++++++++++++++
  include/xen/mem_reservation.h |  29 ++++++++
  4 files changed, 170 insertions(+), 65 deletions(-)
  create mode 100644 drivers/xen/mem-reservation.c
  create mode 100644 include/xen/mem_reservation.h
Can you please name this include/xen/mem-reservation.h ?

Will rename
diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
index 451e833f5931..3c87b0c3aca6 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..57b482d67a3a 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);
@@ -486,9 +475,7 @@ static enum bp_state increase_reservation(unsigned long 
nr_pages)
                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 +483,7 @@ 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 +500,6 @@ 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 +513,7 @@ 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);
        }
@@ -575,25 +535,8 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
                /* 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 +544,7 @@ 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..29882e4324f5
--- /dev/null
+++ b/drivers/xen/mem-reservation.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/******************************************************************************
+ * 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 <linux/kernel.h>
+#include <linux/slab.h>
+
+#include <asm/tlb.h>
+#include <asm/xen/hypercall.h>
+
+#include <xen/interface/memory.h>
+#include <xen/page.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)
+
+void xenmem_reservation_scrub_page(struct page *page)
+{
+#ifdef CONFIG_XEN_SCRUB_PAGES
+       clear_highpage(page);
+#endif
+}
+EXPORT_SYMBOL(xenmem_reservation_scrub_page);
EXPORT_SYMBOL_GPL()

Multiple times below, too.
Ok, will change to _GPL
As a general rule of thumb: new exports should all be
EXPORT_SYMBOL_GPL() if you can't give a reason why they shouldn't be.


Juergen
Thank you,
Oleksandr

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