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Commit 08ece5bb authored by Zoltan Kiss's avatar Zoltan Kiss Committed by Konrad Rzeszutek Wilk
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xen/grant-table: Avoid m2p_override during mapping 



The grant mapping API does m2p_override unnecessarily: only gntdev needs it,
for blkback and future netback patches it just cause a lock contention, as
those pages never go to userspace. Therefore this series does the following:
- the original functions were renamed to __gnttab_[un]map_refs, with a new
  parameter m2p_override
- based on m2p_override either they follow the original behaviour, or just set
  the private flag and call set_phys_to_machine
- gnttab_[un]map_refs are now a wrapper to call __gnttab_[un]map_refs with
  m2p_override false
- a new function gnttab_[un]map_refs_userspace provides the old behaviour

It also removes a stray space from page.h and change ret to 0 if
XENFEAT_auto_translated_physmap, as that is the only possible return value
there.

v2:
- move the storing of the old mfn in page->index to gnttab_map_refs
- move the function header update to a separate patch

v3:
- a new approach to retain old behaviour where it needed
- squash the patches into one

v4:
- move out the common bits from m2p* functions, and pass pfn/mfn as parameter
- clear page->private before doing anything with the page, so m2p_find_override
  won't race with this

v5:
- change return value handling in __gnttab_[un]map_refs
- remove a stray space in page.h
- add detail why ret = 0 now at some places

v6:
- don't pass pfn to m2p* functions, just get it locally

Signed-off-by: default avatarZoltan Kiss <zoltan.kiss@citrix.com>
Suggested-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Acked-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Acked-by: default avatarStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 47c54205

arch/x86/include/asm/xen/page.h

+3 −2
Original line number Diff line number Diff line
@@ -52,7 +52,8 @@ extern unsigned long set_phys_range_identity(unsigned long pfn_s, 
extern int m2p_add_override(unsigned long mfn, struct page *page,

			    struct gnttab_map_grant_ref *kmap_op);

extern int m2p_remove_override(struct page *page,

				struct gnttab_map_grant_ref *kmap_op);

			       struct gnttab_map_grant_ref *kmap_op,

			       unsigned long mfn);

extern struct page *m2p_find_override(unsigned long mfn);

extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);

arch/x86/xen/p2m.c

+2 −15
Original line number Diff line number Diff line
@@ -899,13 +899,6 @@ int m2p_add_override(unsigned long mfn, struct page *page, 
					"m2p_add_override: pfn %lx not mapped", pfn))

			return -EINVAL;

	}

	WARN_ON(PagePrivate(page));

	SetPagePrivate(page);

	set_page_private(page, mfn);

	page->index = pfn_to_mfn(pfn);



	if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))

		return -ENOMEM;



	if (kmap_op != NULL) {

		if (!PageHighMem(page)) {
@@ -944,19 +937,16 @@ int m2p_add_override(unsigned long mfn, struct page *page, 
}

EXPORT_SYMBOL_GPL(m2p_add_override);

int m2p_remove_override(struct page *page,

		struct gnttab_map_grant_ref *kmap_op)

			struct gnttab_map_grant_ref *kmap_op,

			unsigned long mfn)

{

	unsigned long flags;

	unsigned long mfn;

	unsigned long pfn;

	unsigned long uninitialized_var(address);

	unsigned level;

	pte_t *ptep = NULL;



	pfn = page_to_pfn(page);

	mfn = get_phys_to_machine(pfn);

	if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT))

		return -EINVAL;



	if (!PageHighMem(page)) {

		address = (unsigned long)__va(pfn << PAGE_SHIFT);
@@ -970,10 +960,7 @@ int m2p_remove_override(struct page *page, 
	spin_lock_irqsave(&m2p_override_lock, flags);

	list_del(&page->lru);

	spin_unlock_irqrestore(&m2p_override_lock, flags);

	WARN_ON(!PagePrivate(page));

	ClearPagePrivate(page);



	set_phys_to_machine(pfn, page->index);

	if (kmap_op != NULL) {

		if (!PageHighMem(page)) {

			struct multicall_space mcs;

drivers/block/xen-blkback/blkback.c

+6 −9
Original line number Diff line number Diff line
@@ -285,8 +285,7 @@ static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root, 


		if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||

			!rb_next(&persistent_gnt->node)) {

			ret = gnttab_unmap_refs(unmap, NULL, pages,

				segs_to_unmap);

			ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);

			BUG_ON(ret);

			put_free_pages(blkif, pages, segs_to_unmap);

			segs_to_unmap = 0;
@@ -321,8 +320,7 @@ static void unmap_purged_grants(struct work_struct *work) 
		pages[segs_to_unmap] = persistent_gnt->page;



		if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) {

			ret = gnttab_unmap_refs(unmap, NULL, pages,

				segs_to_unmap);

			ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);

			BUG_ON(ret);

			put_free_pages(blkif, pages, segs_to_unmap);

			segs_to_unmap = 0;
@@ -330,7 +328,7 @@ static void unmap_purged_grants(struct work_struct *work) 
		kfree(persistent_gnt);

	}

	if (segs_to_unmap > 0) {

		ret = gnttab_unmap_refs(unmap, NULL, pages, segs_to_unmap);

		ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);

		BUG_ON(ret);

		put_free_pages(blkif, pages, segs_to_unmap);

	}
@@ -670,15 +668,14 @@ static void xen_blkbk_unmap(struct xen_blkif *blkif, 
				    GNTMAP_host_map, pages[i]->handle);

		pages[i]->handle = BLKBACK_INVALID_HANDLE;

		if (++invcount == BLKIF_MAX_SEGMENTS_PER_REQUEST) {

			ret = gnttab_unmap_refs(unmap, NULL, unmap_pages,

			                        invcount);

			ret = gnttab_unmap_refs(unmap, unmap_pages, invcount);

			BUG_ON(ret);

			put_free_pages(blkif, unmap_pages, invcount);

			invcount = 0;

		}

	}

	if (invcount) {

		ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);

		ret = gnttab_unmap_refs(unmap, unmap_pages, invcount);

		BUG_ON(ret);

		put_free_pages(blkif, unmap_pages, invcount);

	}
@@ -740,7 +737,7 @@ again: 
	}



	if (segs_to_map) {

		ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);

		ret = gnttab_map_refs(map, pages_to_gnt, segs_to_map);

		BUG_ON(ret);

	}

drivers/xen/gntdev.c

+8 −5
Original line number Diff line number Diff line
@@ -284,8 +284,10 @@ static int map_grant_pages(struct grant_map *map) 
	}



	pr_debug("map %d+%d\n", map->index, map->count);

	err = gnttab_map_refs(map->map_ops, use_ptemod ? map->kmap_ops : NULL,

			map->pages, map->count);

	err = gnttab_map_refs_userspace(map->map_ops,

					use_ptemod ? map->kmap_ops : NULL,

					map->pages,

					map->count);

	if (err)

		return err;
@@ -315,8 +317,9 @@ static int __unmap_grant_pages(struct grant_map *map, int offset, int pages) 
		}

	}



	err = gnttab_unmap_refs(map->unmap_ops + offset,

			use_ptemod ? map->kmap_ops + offset : NULL, map->pages + offset,

	err = gnttab_unmap_refs_userspace(map->unmap_ops + offset,

					  use_ptemod ? map->kmap_ops + offset : NULL,

					  map->pages + offset,

					  pages);

	if (err)

		return err;

drivers/xen/grant-table.c

+76 −13
Original line number Diff line number Diff line
@@ -928,15 +928,17 @@ void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count) 
}

EXPORT_SYMBOL_GPL(gnttab_batch_copy);



int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,

int __gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,

		    struct gnttab_map_grant_ref *kmap_ops,

		    struct page **pages, unsigned int count)

		    struct page **pages, unsigned int count,

		    bool m2p_override)

{

	int i, ret;

	bool lazy = false;

	pte_t *pte;

	unsigned long mfn;

	unsigned long mfn, pfn;



	BUG_ON(kmap_ops && !m2p_override);

	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map_ops, count);

	if (ret)

		return ret;
@@ -955,10 +957,12 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops, 
			set_phys_to_machine(map_ops[i].host_addr >> PAGE_SHIFT,

					map_ops[i].dev_bus_addr >> PAGE_SHIFT);

		}

		return ret;

		return 0;

	}



	if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {

	if (m2p_override &&

	    !in_interrupt() &&

	    paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {

		arch_enter_lazy_mmu_mode();

		lazy = true;

	}
@@ -975,6 +979,18 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops, 
		} else {

			mfn = PFN_DOWN(map_ops[i].dev_bus_addr);

		}

		pfn = page_to_pfn(pages[i]);



		WARN_ON(PagePrivate(pages[i]));

		SetPagePrivate(pages[i]);

		set_page_private(pages[i], mfn);



		pages[i]->index = pfn_to_mfn(pfn);

		if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {

			ret = -ENOMEM;

			goto out;

		}

		if (m2p_override)

			ret = m2p_add_override(mfn, pages[i], kmap_ops ?

					       &kmap_ops[i] : NULL);

		if (ret)
@@ -987,15 +1003,32 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops, 


	return ret;

}



int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,

		    struct page **pages, unsigned int count)

{

	return __gnttab_map_refs(map_ops, NULL, pages, count, false);

}

EXPORT_SYMBOL_GPL(gnttab_map_refs);



int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,

int gnttab_map_refs_userspace(struct gnttab_map_grant_ref *map_ops,

			      struct gnttab_map_grant_ref *kmap_ops,

			      struct page **pages, unsigned int count)

{

	return __gnttab_map_refs(map_ops, kmap_ops, pages, count, true);

}

EXPORT_SYMBOL_GPL(gnttab_map_refs_userspace);



int __gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,

		      struct gnttab_map_grant_ref *kmap_ops,

		      struct page **pages, unsigned int count,

		      bool m2p_override)

{

	int i, ret;

	bool lazy = false;

	unsigned long pfn, mfn;



	BUG_ON(kmap_ops && !m2p_override);

	ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count);

	if (ret)

		return ret;
@@ -1006,17 +1039,33 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops, 
			set_phys_to_machine(unmap_ops[i].host_addr >> PAGE_SHIFT,

					INVALID_P2M_ENTRY);

		}

		return ret;

		return 0;

	}



	if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {

	if (m2p_override &&

	    !in_interrupt() &&

	    paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {

		arch_enter_lazy_mmu_mode();

		lazy = true;

	}



	for (i = 0; i < count; i++) {

		ret = m2p_remove_override(pages[i], kmap_ops ?

				       &kmap_ops[i] : NULL);

		pfn = page_to_pfn(pages[i]);

		mfn = get_phys_to_machine(pfn);

		if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {

			ret = -EINVAL;

			goto out;

		}



		set_page_private(pages[i], INVALID_P2M_ENTRY);

		WARN_ON(!PagePrivate(pages[i]));

		ClearPagePrivate(pages[i]);

		set_phys_to_machine(pfn, pages[i]->index);

		if (m2p_override)

			ret = m2p_remove_override(pages[i],

						  kmap_ops ?

						   &kmap_ops[i] : NULL,

						  mfn);

		if (ret)

			goto out;

	}
@@ -1027,8 +1076,22 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops, 


	return ret;

}



int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *map_ops,

		    struct page **pages, unsigned int count)

{

	return __gnttab_unmap_refs(map_ops, NULL, pages, count, false);

}

EXPORT_SYMBOL_GPL(gnttab_unmap_refs);



int gnttab_unmap_refs_userspace(struct gnttab_unmap_grant_ref *map_ops,

				struct gnttab_map_grant_ref *kmap_ops,

				struct page **pages, unsigned int count)

{

	return __gnttab_unmap_refs(map_ops, kmap_ops, pages, count, true);

}

EXPORT_SYMBOL_GPL(gnttab_unmap_refs_userspace);



static unsigned nr_status_frames(unsigned nr_grant_frames)

{

	BUG_ON(grefs_per_grant_frame == 0);