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SubjectRe: [PATCH 2/8] xen/balloon: Move common memory reservation routines to a module
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On 05/29/2018 09:04 PM, Boris Ostrovsky wrote:
> On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote:
>> 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
> IIUIC this is not really a module, it's a common file.
Sure, will put "file" here
>
>> 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]);
>
> Can you make a single call to xenmem_reservation_va_mapping_update(rc,
> ...)? You need to keep track of pages but presumable they can be put
> into an array (or a list). In fact, perhaps we can have
> balloon_retrieve() return a set of pages.
This is actually how it is used later on for dma-buf, but I just didn't want
to alter original balloon code too much, but this can be done, in order
of simplicity:

1. Similar to frame_list, e.g. static array of struct page* of size
ARRAY_SIZE(frame_list):
more static memory is used, but no allocations

2. Allocated at run-time with kcalloc: allocation can fail

3. Make balloon_retrieve() return a set of pages: will require
list/array allocation
and handling, allocation may fail, balloon_retrieve prototype change

Could you please tell which of the above will fit better?

>
>
>
>>
>> /* 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);
>
> and here too.
see above
>
>>
>> - 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
>
> Why is this "OR MIT"? The original file was licensed GPLv2 only.
Will fix - I was not sure about the license to be used here, thanks
>
>> +
>> +/******************************************************************************
>> + * 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 */
> and here too.
will fix
>
> -boris
>
Thank you,
Oleksandr
>> +
>> +/*
>> + * 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

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