Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753684AbaAWXfO (ORCPT ); Thu, 23 Jan 2014 18:35:14 -0500 Received: from smtp.citrix.com ([66.165.176.89]:48530 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751616AbaAWXfL (ORCPT ); Thu, 23 Jan 2014 18:35:11 -0500 X-IronPort-AV: E=Sophos;i="4.95,709,1384300800"; d="scan'208";a="95990490" Date: Thu, 23 Jan 2014 23:34:01 +0000 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: Zoltan Kiss CC: , , , , , Subject: Re: [PATCH v6] xen/grant-table: Avoid m2p_override during mapping In-Reply-To: <1390512224-27296-1-git-send-email-zoltan.kiss@citrix.com> Message-ID: References: <1390512224-27296-1-git-send-email-zoltan.kiss@citrix.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 23 Jan 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 > - 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: Zoltan Kiss > Suggested-by: David Vrabel Reviewed-by: Stefano Stabellini > arch/x86/include/asm/xen/page.h | 5 +- > arch/x86/xen/p2m.c | 17 +------ > drivers/block/xen-blkback/blkback.c | 15 +++--- > drivers/xen/gntdev.c | 13 +++-- > drivers/xen/grant-table.c | 89 ++++++++++++++++++++++++++++++----- > include/xen/grant_table.h | 8 +++- > 6 files changed, 101 insertions(+), 46 deletions(-) > > diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h > index b913915..ce47243 100644 > --- a/arch/x86/include/asm/xen/page.h > +++ b/arch/x86/include/asm/xen/page.h > @@ -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); > > @@ -121,7 +122,7 @@ 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 2ae8699..bd4724b 100644 > --- a/arch/x86/xen/p2m.c > +++ b/arch/x86/xen/p2m.c > @@ -888,13 +888,6 @@ 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)) { > @@ -933,19 +926,16 @@ 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); > @@ -959,10 +949,7 @@ 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 e41c79c..e652c0e 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 aa846a4..e4ddfeb 100644 > --- a/drivers/xen/grant-table.c > +++ b/drivers/xen/grant-table.c > @@ -880,15 +880,17 @@ 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; > @@ -907,10 +909,12 @@ 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; > } > @@ -927,8 +931,20 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops, > } else { > mfn = PFN_DOWN(map_ops[i].dev_bus_addr); > } > - ret = m2p_add_override(mfn, pages[i], kmap_ops ? > - &kmap_ops[i] : NULL); > + 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; > } > @@ -939,15 +955,32 @@ 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) > + 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; > @@ -958,17 +991,33 @@ 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; > } > @@ -979,8 +1028,22 @@ 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); > diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h > index 694dcaf..9a919b1 100644 > --- a/include/xen/grant_table.h > +++ b/include/xen/grant_table.h > @@ -184,11 +184,15 @@ unsigned int gnttab_max_grant_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 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/