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SubjectRe: [PATCH v9] xen/grant-table: Avoid m2p_override during mapping
On Wed, 12 Feb 2014, Zoltan Kiss wrote:
> 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
> - arch specific functions *_foreign_p2m_mapping do everything after the
> hypercall
> - it cuts out common parts from m2p_*_override functions to
> *_foreign_p2m_mapping functions
> - 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.
>
> Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
> Original-by: Anthony Liguori <aliguori@amazon.com>
> ---
> 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
>
> v7:
> - the previous version broke build on ARM, as there is no need for those p2m
> changes. I've put them into arch specific functions, which are stubs on arm
>
> v8:
> - give credit to Anthony Liguori who submitted a very similar patch originally:
> http://marc.info/?i=1384307336-5328-1-git-send-email-anthony%40codemonkey.ws
> - create ARM stub for get_phys_to_machine
> - move definition of mfn in __gnttab_unmap_refs to the right place
>
> v9:
> - move everything after the hypercalls into set/clear_foreign_p2m_mapping
> - m2p override functions became unnecessary on ARM therefore
>
> arch/arm/include/asm/xen/page.h | 19 +++---
> arch/arm/xen/p2m.c | 34 ++++++++++
> arch/x86/include/asm/xen/page.h | 13 +++-
> arch/x86/xen/p2m.c | 127 ++++++++++++++++++++++++++++++-----
> drivers/block/xen-blkback/blkback.c | 15 ++---
> drivers/xen/gntdev.c | 13 ++--
> drivers/xen/grant-table.c | 115 +++++++++++--------------------
> include/xen/grant_table.h | 8 ++-
> 8 files changed, 227 insertions(+), 117 deletions(-)
>
> diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
> index e0965ab..4eaeb3f 100644
> --- a/arch/arm/include/asm/xen/page.h
> +++ b/arch/arm/include/asm/xen/page.h
> @@ -97,16 +97,15 @@ static inline pte_t *lookup_address(unsigned long address, unsigned int *level)
> return NULL;
> }
>
> -static inline int m2p_add_override(unsigned long mfn, struct page *page,
> - struct gnttab_map_grant_ref *kmap_op)
> -{
> - return 0;
> -}
> -
> -static inline int m2p_remove_override(struct page *page, bool clear_pte)
> -{
> - return 0;
> -}
> +extern int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
> + struct gnttab_map_grant_ref *kmap_ops,
> + struct page **pages, unsigned int count,
> + bool m2p_override);
> +
> +extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
> + struct gnttab_map_grant_ref *kmap_ops,
> + struct page **pages, unsigned int count,
> + bool m2p_override);

Much much better.
The only comment I have is about this m2p_override boolean parameter.
m2p_override is now meaningless in this context, what we really want to
let the arch specific implementation know is whether the mapping is a
kernel only mapping or a userspace mapping.
Testing for kmap_ops != NULL might even be enough, but it would not
improve the interface.

Is it possible to realize if the mapping is a userspace mapping by
checking for GNTMAP_application_map in map_ops?
Otherwise I would keep the boolean and rename it to user_mapping.


> bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
> bool __set_phys_to_machine_multi(unsigned long pfn, unsigned long mfn,
> diff --git a/arch/arm/xen/p2m.c b/arch/arm/xen/p2m.c
> index b31ee1b2..74d977c 100644
> --- a/arch/arm/xen/p2m.c
> +++ b/arch/arm/xen/p2m.c
> @@ -146,6 +146,40 @@ unsigned long __mfn_to_pfn(unsigned long mfn)
> }
> EXPORT_SYMBOL_GPL(__mfn_to_pfn);
>
> +int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
> + struct gnttab_map_grant_ref *kmap_ops,
> + struct page **pages, unsigned int count,
> + bool m2p_override)
> +{
> + int i;
> +
> + for (i = 0; i < count; i++) {
> + if (map_ops[i].status)
> + continue;
> + set_phys_to_machine(map_ops[i].host_addr >> PAGE_SHIFT,
> + map_ops[i].dev_bus_addr >> PAGE_SHIFT);
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
> +
> +int clear_foreign_p2m_mapping(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;
> +
> + for (i = 0; i < count; i++) {
> + set_phys_to_machine(unmap_ops[i].host_addr >> PAGE_SHIFT,
> + INVALID_P2M_ENTRY);
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
> +
> bool __set_phys_to_machine_multi(unsigned long pfn,
> unsigned long mfn, unsigned long nr_pages)
> {
> diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
> index 3e276eb..9edc8a8 100644
> --- a/arch/x86/include/asm/xen/page.h
> +++ b/arch/x86/include/asm/xen/page.h
> @@ -49,10 +49,19 @@ extern bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
> extern unsigned long set_phys_range_identity(unsigned long pfn_s,
> unsigned long pfn_e);
>
> +extern int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
> + struct gnttab_map_grant_ref *kmap_ops,
> + struct page **pages, unsigned int count,
> + bool m2p_override);
> extern int m2p_add_override(unsigned long mfn, struct page *page,
> struct gnttab_map_grant_ref *kmap_op);
> +extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
> + struct gnttab_map_grant_ref *kmap_ops,
> + struct page **pages, unsigned int count,
> + bool m2p_override);
> 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);
>
> @@ -121,7 +130,7 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn)
> pfn = m2p_find_override_pfn(mfn, ~0);
> }
>
> - /*
> + /*
> * pfn is ~0 if there are no entries in the m2p for mfn or if the
> * entry doesn't map back to the mfn and m2p_override doesn't have a
> * valid entry for it.
> diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
> index 696c694..305af27 100644
> --- a/arch/x86/xen/p2m.c
> +++ b/arch/x86/xen/p2m.c
> @@ -881,6 +881,67 @@ static unsigned long mfn_hash(unsigned long mfn)
> return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
> }
>
> +int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
> + struct gnttab_map_grant_ref *kmap_ops,
> + struct page **pages, unsigned int count,
> + bool m2p_override)
> +{
> + int i, ret = 0;
> + bool lazy = false;
> + pte_t *pte;
> +
> + if (xen_feature(XENFEAT_auto_translated_physmap))
> + return 0;
> +
> + 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++) {
> + unsigned long mfn, pfn;
> +
> + /* Do not add to override if the map failed. */
> + if (map_ops[i].status)
> + continue;
> +
> + if (map_ops[i].flags & GNTMAP_contains_pte) {
> + pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
> + (map_ops[i].host_addr & ~PAGE_MASK));
> + mfn = pte_mfn(*pte);
> + } 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)
> + goto out;
> + }
> + }
> +
> +out:
> + if (lazy)
> + arch_leave_lazy_mmu_mode();
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
> +
> /* Add an MFN override for a particular page */
> int m2p_add_override(unsigned long mfn, struct page *page,
> struct gnttab_map_grant_ref *kmap_op)
> @@ -899,13 +960,6 @@ 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)) {
> @@ -943,20 +997,66 @@ int m2p_add_override(unsigned long mfn, struct page *page,
> return 0;
> }
> EXPORT_SYMBOL_GPL(m2p_add_override);
> +
> +int clear_foreign_p2m_mapping(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 = 0;
> + bool lazy = false;
> +
> + if (xen_feature(XENFEAT_auto_translated_physmap))
> + return 0;
> +
> + 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++) {
> + unsigned long mfn = get_phys_to_machine(page_to_pfn(pages[i]));
> + unsigned long pfn = page_to_pfn(pages[i]);
> +
> + 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;
> + }
> +
> +out:
> + if (lazy)
> + arch_leave_lazy_mmu_mode();
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
> +
> 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 +1070,7 @@ 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;
> diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
> index 6620b73..875025f 100644
> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -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);
> }
>
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index 073b4a1..34a2704 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -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;
>
> @@ -315,9 +317,10 @@ 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,
> - pages);
> + err = gnttab_unmap_refs_userspace(map->unmap_ops + offset,
> + use_ptemod ? map->kmap_ops + offset : NULL,
> + map->pages + offset,
> + pages);
> if (err)
> return err;
>
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index 1ce1c40..5efacf8 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -928,15 +928,14 @@ 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,
> - struct gnttab_map_grant_ref *kmap_ops,
> - struct page **pages, unsigned int count)
> +static int __gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
> + struct gnttab_map_grant_ref *kmap_ops,
> + struct page **pages, unsigned int count,
> + bool m2p_override)
> {
> int i, ret;
> - bool lazy = false;
> - pte_t *pte;
> - unsigned long mfn;
>
> + BUG_ON(kmap_ops && !m2p_override);
> ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map_ops, count);
> if (ret)
> return ret;
> @@ -947,88 +946,56 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
> gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, map_ops + i,
> &map_ops[i].status, __func__);
>
> - /* this is basically a nop on x86 */
> - if (xen_feature(XENFEAT_auto_translated_physmap)) {
> - for (i = 0; i < count; i++) {
> - if (map_ops[i].status)
> - continue;
> - set_phys_to_machine(map_ops[i].host_addr >> PAGE_SHIFT,
> - map_ops[i].dev_bus_addr >> PAGE_SHIFT);
> - }
> - return ret;
> - }
> -
> - if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
> - arch_enter_lazy_mmu_mode();
> - lazy = true;
> - }
> -
> - for (i = 0; i < count; i++) {
> - /* Do not add to override if the map failed. */
> - if (map_ops[i].status)
> - continue;
> -
> - if (map_ops[i].flags & GNTMAP_contains_pte) {
> - pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
> - (map_ops[i].host_addr & ~PAGE_MASK));
> - mfn = pte_mfn(*pte);
> - } else {
> - mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
> - }
> - ret = m2p_add_override(mfn, pages[i], kmap_ops ?
> - &kmap_ops[i] : NULL);
> - if (ret)
> - goto out;
> - }
> -
> - out:
> - if (lazy)
> - arch_leave_lazy_mmu_mode();
> + return set_foreign_p2m_mapping(map_ops, kmap_ops, pages, count,
> + m2p_override);
> +}
>
> - 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,
> - struct gnttab_map_grant_ref *kmap_ops,
> - struct page **pages, unsigned int count)
> +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)
> {
> - int i, ret;
> - bool lazy = false;
> + return __gnttab_map_refs(map_ops, kmap_ops, pages, count, true);
> +}
> +EXPORT_SYMBOL_GPL(gnttab_map_refs_userspace);
> +
> +static 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 ret;
>
> + BUG_ON(kmap_ops && !m2p_override);
> ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count);
> if (ret)
> return ret;
>
> - /* this is basically a nop on x86 */
> - if (xen_feature(XENFEAT_auto_translated_physmap)) {
> - for (i = 0; i < count; i++) {
> - set_phys_to_machine(unmap_ops[i].host_addr >> PAGE_SHIFT,
> - INVALID_P2M_ENTRY);
> - }
> - return ret;
> - }
> -
> - if (!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);
> - if (ret)
> - goto out;
> - }
> -
> - out:
> - if (lazy)
> - arch_leave_lazy_mmu_mode();
> + return clear_foreign_p2m_mapping(unmap_ops, kmap_ops, pages, count,
> + m2p_override);
> +}
>
> - 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);
> diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
> index 5acb1e4..2541c96 100644
> --- a/include/xen/grant_table.h
> +++ b/include/xen/grant_table.h
> @@ -191,11 +191,15 @@ void gnttab_free_auto_xlat_frames(void);
> #define gnttab_map_vaddr(map) ((void *)(map.host_virt_addr))
>
> int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
> - struct gnttab_map_grant_ref *kmap_ops,
> struct page **pages, unsigned int count);
> +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);
> int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
> - struct gnttab_map_grant_ref *kunmap_ops,
> struct page **pages, unsigned int count);
> +int gnttab_unmap_refs_userspace(struct gnttab_unmap_grant_ref *unmap_ops,
> + struct gnttab_map_grant_ref *kunmap_ops,
> + struct page **pages, unsigned int count);
>
> /* Perform a batch of grant map/copy operations. Retry every batch slot
> * for which the hypervisor returns GNTST_eagain. This is typically due
>


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