xen/balloon: Bring alloc(free)_xenballooned_pages helpers back

This patch rolls back some of the changes introduced by commit 121f2faca2c0a "xen/balloon: rename alloc/free_xenballooned_pages" in order to make possible to still allocate xenballooned pages if CONFIG_XEN_UNPOPULATED_ALLOC is enabled. On Arm the unpopulated pages will be allocated on top of extended regions provided by Xen via device-tree (the subsequent patches will add required bits to support unpopulated-alloc feature on Arm). The problem is that extended regions feature has been introduced into Xen quite recently (during 4.16 release cycle). So this effectively means that Linux must only use unpopulated-alloc on Arm if it is running on "new Xen" which advertises these regions. But, it will only be known after parsing the "hypervisor" node at boot time, so before doing that we cannot assume anything. In order to keep working if CONFIG_XEN_UNPOPULATED_ALLOC is enabled and the extended regions are not advertised (Linux is running on "old Xen", etc) we need the fallback to alloc_xenballooned_pages(). This way we wouldn't reduce the amount of memory usable (wasting RAM pages) for any of the external mappings anymore (and eliminate XSA-300) with "new Xen", but would be still functional ballooning out RAM pages with "old Xen". Also rename alloc(free)_xenballooned_pages to xen_alloc(free)_ballooned_pages and make xen_alloc(free)_unpopulated_pages static inline in xen.h if CONFIG_XEN_UNPOPULATED_ALLOC is disabled.

Oleksandr Tyshchenko committed 4 years ago

Commit 9dd060a1 parent 5e1cdb83 files · +26 −11Browse files

Unified · Split

3 files

drivers/xen/balloon.c +9 −11
include/xen/balloon.h +3 −0
include/xen/xen.h +14 −0

drivers/xen/balloon.c+9−11

@@ -581,7 +581,6 @@ void balloon_set_new_target(unsigned long target) · 580 unmodified lines
581	581	}
582	582	EXPORT_SYMBOL_GPL(balloon_set_new_target);
583	583
584		−#ifndef CONFIG_XEN_UNPOPULATED_ALLOC
585	584	static int add_ballooned_pages(unsigned int nr_pages)
586	585	{
587	586	enum bp_state st;
@@ -610,12 +609,12 @@ static int add_ballooned_pages(unsigned int nr_pages) · 22 unmodified lines
610	609	}
611	610
612	611	/**
613		− * xen_alloc_unpopulated_pages - get pages that have been ballooned out
	612	+ * xen_alloc_ballooned_pages - get pages that have been ballooned out
614	613	* @nr_pages: Number of pages to get
615	614	* @pages: pages returned
616	615	* @return 0 on success, error otherwise
617	616	*/
618		−int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page **pages)
	617	+int xen_alloc_ballooned_pages(unsigned int nr_pages, struct page **pages)
619	618	{
620	619	unsigned int pgno = 0;
621	620	struct page *page;
@@ -652,23 +651,23 @@ int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page **pages) · 30 unmodified lines
652	651	return 0;
653	652	out_undo:
654	653	mutex_unlock(&balloon_mutex);
655		− xen_free_unpopulated_pages(pgno, pages);
	654	+ xen_free_ballooned_pages(pgno, pages);
656	655	/*
657		− * NB: free_xenballooned_pages will only subtract pgno pages, but since
	656	+ * NB: xen_free_ballooned_pages will only subtract pgno pages, but since
658	657	* target_unpopulated is incremented with nr_pages at the start we need
659	658	* to remove the remaining ones also, or accounting will be screwed.
660	659	*/
661	660	balloon_stats.target_unpopulated -= nr_pages - pgno;
662	661	return ret;
663	662	}
664		−EXPORT_SYMBOL(xen_alloc_unpopulated_pages);
	663	+EXPORT_SYMBOL(xen_alloc_ballooned_pages);
665	664
666	665	/**
667		− * xen_free_unpopulated_pages - return pages retrieved with get_ballooned_pages
	666	+ * xen_free_ballooned_pages - return pages retrieved with get_ballooned_pages
668	667	* @nr_pages: Number of pages
669	668	* @pages: pages to return
670	669	*/
671		−void xen_free_unpopulated_pages(unsigned int nr_pages, struct page **pages)
	670	+void xen_free_ballooned_pages(unsigned int nr_pages, struct page **pages)
672	671	{
673	672	unsigned int i;
674	673
@@ -687,9 +686,9 @@ void xen_free_unpopulated_pages(unsigned int nr_pages, struct page **pages) · 12 unmodified lines
687	686
688	687	mutex_unlock(&balloon_mutex);
689	688	}
690		−EXPORT_SYMBOL(xen_free_unpopulated_pages);
	689	+EXPORT_SYMBOL(xen_free_ballooned_pages);
691	690
692		−#if defined(CONFIG_XEN_PV)
	691	+#if defined(CONFIG_XEN_PV) && !defined(CONFIG_XEN_UNPOPULATED_ALLOC)
693	692	static void __init balloon_add_region(unsigned long start_pfn,
694	693	unsigned long pages)
695	694	{
@@ -712,7 +711,6 @@ static void __init balloon_add_region(unsigned long start_pfn, · 16 unmodified lines
712	711	balloon_stats.total_pages += extra_pfn_end - start_pfn;
713	712	}
714	713	#endif
715		−#endif
716	714
717	715	static int __init balloon_init(void)
718	716	{

include/xen/balloon.h+3−0

@@ -26,6 +26,9 @@ extern struct balloon_stats balloon_stats; · 25 unmodified lines
26	26
27	27	void balloon_set_new_target(unsigned long target);
28	28
	29	+int xen_alloc_ballooned_pages(unsigned int nr_pages, struct page **pages);
	30	+void xen_free_ballooned_pages(unsigned int nr_pages, struct page **pages);
	31	+
29	32	#ifdef CONFIG_XEN_BALLOON
30	33	void xen_balloon_init(void);
31	34	#else

include/xen/xen.h+14−0

@@ -52,7 +52,21 @@ bool xen_biovec_phys_mergeable(const struct bio_vec *vec1, · 51 unmodified lines
52	52	extern u64 xen_saved_max_mem_size;
53	53	#endif
54	54
	55	+#ifdef CONFIG_XEN_UNPOPULATED_ALLOC
55	56	int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page **pages);
56	57	void xen_free_unpopulated_pages(unsigned int nr_pages, struct page **pages);
	58	+#else
	59	+#include <xen/balloon.h>
	60	+static inline int xen_alloc_unpopulated_pages(unsigned int nr_pages,
	61	+ struct page **pages)
	62	+{
	63	+ return xen_alloc_ballooned_pages(nr_pages, pages);
	64	+}
	65	+static inline void xen_free_unpopulated_pages(unsigned int nr_pages,
	66	+ struct page **pages)
	67	+{
	68	+ xen_free_ballooned_pages(nr_pages, pages);
	69	+}
	70	+#endif
57	71
58	72	#endif /* _XEN_XEN_H */

xen/balloon: Bring alloc(free)_xenballooned_pages helpers back

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