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    Subject[PATCH 2/8] xen/balloon: Move common memory reservation routines to a module
    Date
    From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

    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@epam.com>
    ---
    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

    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);
    +
    +void xenmem_reservation_va_mapping_update(unsigned long count,
    + struct page **pages,
    + xen_pfn_t *frames)
    +{
    +#ifdef CONFIG_XEN_HAVE_PVMMU
    + int i;
    +
    + for (i = 0; i < count; i++) {
    + struct page *page;
    +
    + page = pages[i];
    + BUG_ON(page == NULL);
    +
    + /*
    + * 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, 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);
    + }
    + }
    + }
    +#endif
    +}
    +EXPORT_SYMBOL(xenmem_reservation_va_mapping_update);
    +
    +void xenmem_reservation_va_mapping_reset(unsigned long count,
    + struct page **pages)
    +{
    +#ifdef CONFIG_XEN_HAVE_PVMMU
    + int i;
    +
    + for (i = 0; i < count; i++) {
    + /*
    + * 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)) {
    + struct page *page = pages[i];
    + unsigned long pfn = page_to_pfn(page);
    +
    + 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);
    + }
    + }
    +#endif
    +}
    +EXPORT_SYMBOL(xenmem_reservation_va_mapping_reset);
    +
    +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
    + };
    +
    + set_xen_guest_handle(reservation.extent_start, frames);
    + reservation.nr_extents = count;
    + return HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
    +}
    +EXPORT_SYMBOL(xenmem_reservation_increase);
    +
    +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
    + };
    +
    + set_xen_guest_handle(reservation.extent_start, frames);
    + reservation.nr_extents = count;
    + return HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
    +}
    +EXPORT_SYMBOL(xenmem_reservation_decrease);
    diff --git a/include/xen/mem_reservation.h b/include/xen/mem_reservation.h
    new file mode 100644
    index 000000000000..9306d9b8743c
    --- /dev/null
    +++ b/include/xen/mem_reservation.h
    @@ -0,0 +1,29 @@
    +/* 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.
    + */
    +
    +#ifndef _XENMEM_RESERVATION_H
    +#define _XENMEM_RESERVATION_H
    +
    +void xenmem_reservation_scrub_page(struct page *page);
    +
    +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);
    +
    +int xenmem_reservation_increase(int count, xen_pfn_t *frames);
    +
    +int xenmem_reservation_decrease(int count, xen_pfn_t *frames);
    +
    +#endif
    --
    2.17.0
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