[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] xen/arm: introduce put_page_nr and get_page_nr
commit 5951b856d8d0af57212b54f2afbb404b7579bd27 Author: Penny Zheng <Penny.Zheng@xxxxxxx> AuthorDate: Thu Sep 8 21:55:08 2022 +0800 Commit: Stefano Stabellini <stefano.stabellini@xxxxxxx> CommitDate: Fri Sep 9 12:57:59 2022 -0700 xen/arm: introduce put_page_nr and get_page_nr Later, we need to add the right amount of references, which should be the number of borrower domains, to the owner domain. Since we only have get_page() to increment the page reference by 1, a loop is needed per page, which is inefficient and time-consuming. To save the loop time, this commit introduces a set of new helpers put_page_nr() and get_page_nr() to increment/drop the page reference by nr. Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx> Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx> --- xen/arch/arm/include/asm/mm.h | 4 ++++ xen/arch/arm/mm.c | 42 +++++++++++++++++++++++++++++++++--------- 2 files changed, 37 insertions(+), 9 deletions(-) diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h index 7d21120f98..68adcac9fa 100644 --- a/xen/arch/arm/include/asm/mm.h +++ b/xen/arch/arm/include/asm/mm.h @@ -363,6 +363,10 @@ void free_init_memory(void); int guest_physmap_mark_populate_on_demand(struct domain *d, unsigned long gfn, unsigned int order); +extern bool get_page_nr(struct page_info *page, const struct domain *domain, + unsigned long nr); +extern void put_page_nr(struct page_info *page, unsigned long nr); + extern void put_page_type(struct page_info *page); static inline void put_page_and_type(struct page_info *page) { diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c index 11ee49598b..6ccffeaea5 100644 --- a/xen/arch/arm/mm.c +++ b/xen/arch/arm/mm.c @@ -1465,21 +1465,29 @@ long arch_memory_op(int op, XEN_GUEST_HANDLE_PARAM(void) arg) return 0; } -struct domain *page_get_owner_and_reference(struct page_info *page) +static struct domain *page_get_owner_and_nr_reference(struct page_info *page, + unsigned long nr) { unsigned long x, y = page->count_info; struct domain *owner; + /* Restrict nr to avoid "double" overflow */ + if ( nr >= PGC_count_mask ) + { + ASSERT_UNREACHABLE(); + return NULL; + } + do { x = y; /* * Count == 0: Page is not allocated, so we cannot take a reference. * Count == -1: Reference count would wrap, which is invalid. */ - if ( unlikely(((x + 1) & PGC_count_mask) <= 1) ) + if ( unlikely(((x + nr) & PGC_count_mask) <= nr) ) return NULL; } - while ( (y = cmpxchg(&page->count_info, x, x + 1)) != x ); + while ( (y = cmpxchg(&page->count_info, x, x + nr)) != x ); owner = page_get_owner(page); ASSERT(owner); @@ -1487,14 +1495,19 @@ struct domain *page_get_owner_and_reference(struct page_info *page) return owner; } -void put_page(struct page_info *page) +struct domain *page_get_owner_and_reference(struct page_info *page) +{ + return page_get_owner_and_nr_reference(page, 1); +} + +void put_page_nr(struct page_info *page, unsigned long nr) { unsigned long nx, x, y = page->count_info; do { - ASSERT((y & PGC_count_mask) != 0); + ASSERT((y & PGC_count_mask) >= nr); x = y; - nx = x - 1; + nx = x - nr; } while ( unlikely((y = cmpxchg(&page->count_info, x, nx)) != x) ); @@ -1507,19 +1520,30 @@ void put_page(struct page_info *page) } } -bool get_page(struct page_info *page, const struct domain *domain) +void put_page(struct page_info *page) +{ + put_page_nr(page, 1); +} + +bool get_page_nr(struct page_info *page, const struct domain *domain, + unsigned long nr) { - const struct domain *owner = page_get_owner_and_reference(page); + const struct domain *owner = page_get_owner_and_nr_reference(page, nr); if ( likely(owner == domain) ) return true; if ( owner != NULL ) - put_page(page); + put_page_nr(page, nr); return false; } +bool get_page(struct page_info *page, const struct domain *domain) +{ + return get_page_nr(page, domain, 1); +} + /* Common code requires get_page_type and put_page_type. * We don't care about typecounts so we just do the minimum to make it * happy. */ -- generated by git-patchbot for /home/xen/git/xen.git#staging
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