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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen/grant-table: Avoid m2p_override during mapping
On 13/01/14 00:15, 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 patch does the following:
> - move the m2p_override part from grant_[un]map_refs to gntdev, where it is
> needed after mapping operations
> - but move set_phys_to_machine from m2p_override to grant_[un]map_refs,
> because it is needed always
> - update the function prototypes as kmap_ops are no longer needed
>
> Signed-off-by: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
> Suggested-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> ---
> arch/x86/xen/p2m.c | 4 --
> drivers/block/xen-blkback/blkback.c | 15 +++----
> drivers/xen/gntdev.c | 61 ++++++++++++++++++++++++++--
> drivers/xen/grant-table.c | 76
> +++++++++++------------------------
> include/xen/grant_table.h | 2 -
> 5 files changed, 87 insertions(+), 71 deletions(-)
>
> diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
> index 2ae8699..3e78eb9 100644
> --- a/arch/x86/xen/p2m.c
> +++ b/arch/x86/xen/p2m.c
> @@ -893,9 +893,6 @@ int m2p_add_override(unsigned long mfn, struct page *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)) {
> struct multicall_space mcs =
> @@ -962,7 +959,6 @@ int m2p_remove_override(struct page *page,
> 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 e41c79c..3a97342 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -250,6 +250,9 @@ static int find_grant_ptes(pte_t *pte, pgtable_t token,
> static int map_grant_pages(struct grant_map *map)
> {
> int i, err = 0;
> + bool lazy = false;
> + pte_t *pte;
> + unsigned long mfn;
>
> if (!use_ptemod) {
> /* Note: it could already be mapped */
> @@ -284,8 +287,37 @@ 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(map->map_ops, map->pages, map->count);
> + if (err)
> + return err;
> +
> + if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
> + arch_enter_lazy_mmu_mode();
> + lazy = true;
> + }
> +
> + for (i = 0; i < map->count; i++) {
> + /* Do not add to override if the map failed. */
> + if (map->map_ops[i].status)
> + continue;
> +
> + if (map->map_ops[i].flags & GNTMAP_contains_pte) {
> + pte = (pte_t *)
> (mfn_to_virt(PFN_DOWN(map->map_ops[i].host_addr)) +
> + (map->map_ops[i].host_addr & ~PAGE_MASK));
> + mfn = pte_mfn(*pte);
> + } else {
> + mfn = PFN_DOWN(map->map_ops[i].dev_bus_addr);
> + }
> + err = m2p_add_override(mfn,
> + map->pages[i],
> + use_ptemod ? &map->kmap_ops[i] : NULL);
> + if (err)
> + break;
> + }
> +
> + if (lazy)
> + arch_leave_lazy_mmu_mode();
> +
> if (err)
> return err;
>
> @@ -304,6 +336,7 @@ static int map_grant_pages(struct grant_map *map)
> static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
> {
> int i, err = 0;
> + bool lazy = false;
>
> if (map->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
> int pgno = (map->notify.addr >> PAGE_SHIFT);
> @@ -316,8 +349,28 @@ 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);
> + map->pages + offset,
> + pages);
> + if (err)
> + return err;
> +
> + if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
> + arch_enter_lazy_mmu_mode();
> + lazy = true;
> + }
> +
> + for (i = 0; i < pages; i++) {
> + err = m2p_remove_override((map->pages + offset)[i],
> + use_ptemod ?
> + &(map->kmap_ops + offset)[i] :
> + NULL);
> + if (err)
> + break;
> + }
> +
> + if (lazy)
> + arch_leave_lazy_mmu_mode();
> +
> if (err)
> return err;
>
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index aa846a4..59019f2 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -881,11 +881,9 @@ 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)
> {
> int i, ret;
> - bool lazy = false;
> pte_t *pte;
> unsigned long mfn;
>
> @@ -904,49 +902,35 @@ int gnttab_map_refs(struct gnttab_map_grant_ref
> *map_ops,
> 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);
> + if (unlikely(!set_phys_to_machine(map_ops[i].host_addr
> >> PAGE_SHIFT,
> +
> map_ops[i].dev_bus_addr >> PAGE_SHIFT)))
> + return -ENOMEM;
> }
> - 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);
> + } else {
> + for (i = 0; i < count; i++) {
> + 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);
> + }
> + if (unlikely(!set_phys_to_machine(page_to_pfn(pages[i]),
> + FOREIGN_FRAME(mfn))))
> + return -ENOMEM;
> }
> - 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;
> + return 0;
> }
> 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 i, ret;
> - bool lazy = false;
>
> ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops,
> count);
> if (ret)
> @@ -958,26 +942,14 @@ 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;
> - }
> -
> - 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;
> + } else {
> + for (i = 0; i < count; i++) {
> + set_phys_to_machine(page_to_pfn(pages[i]),
> + pages[i]->index);
You seem to relay on page->index containing the old mfn, but I don't see
it being set on gnttab_map_refs (it's only set on m2p_add_override
AFAICT), maybe I'm missing something?
Roger.
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