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Date: Sun, 02 Feb 2014 10:29:58 +0000
From: Julien Grall <julien.grall@...aro.org>
To: Stefano Stabellini <stefano.stabellini@...citrix.com>,
Zoltan Kiss <zoltan.kiss@...rix.com>
CC: jonathan.davies@...rix.com, wei.liu2@...rix.com,
ian.campbell@...rix.com, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org
Subject: Re: [Xen-devel] [PATCH v6] xen/grant-table: Avoid m2p_override during
mapping
On 23/01/14 23:34, Stefano Stabellini wrote:
> 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 <zoltan.kiss@...rix.com>
>> Suggested-by: David Vrabel <david.vrabel@...rix.com>
>
> Reviewed-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
Hello,
This patch is breaking Linux compilation on ARM:
drivers/xen/grant-table.c: In function ‘__gnttab_map_refs’:
drivers/xen/grant-table.c:989:3: error: implicit declaration of function ‘FOREIGN_FRAME’ [-Werror=implicit-function-declaration]
if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
^
drivers/xen/grant-table.c: In function ‘__gnttab_unmap_refs’:
drivers/xen/grant-table.c:1054:3: error: implicit declaration of function ‘get_phys_to_machine’ [-Werror=implicit-function-declaration]
mfn = get_phys_to_machine(pfn);
^
drivers/xen/grant-table.c:1055:43: error: ‘FOREIGN_FRAME_BIT’ undeclared (first use in this function)
if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
^
drivers/xen/grant-table.c:1055:43: note: each undeclared identifier is reported only once for each function it appears in
drivers/xen/grant-table.c:1068:9: error: too many arguments to function ‘m2p_remove_override’
mfn);
^
In file included from include/xen/page.h:4:0,
from drivers/xen/grant-table.c:48:
/local/home/julien/works/midway/linux/arch/arm/include/asm/xen/page.h:106:19: note: declared here
static inline int m2p_remove_override(struct page *page, bool clear_pte)
^
cc1: some warnings being treated as errors
>
>
>
>> 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
>> --
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>>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@...ts.xen.org
> http://lists.xen.org/xen-devel
>
--
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