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

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>]

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