Messages in this thread Patch in this message | | | From | David Hildenbrand <> | Subject | [PATCH] s390x/mm: avoid taking the table lock in gmap_pmd_op_walk() | Date | Mon, 6 Aug 2018 17:54:07 +0200 |
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Right now we temporarily take the page table lock in gmap_pmd_op_walk() even though we know we won't need it (if we can never have 1mb pages mapped into the gmap).
So let's special case this, so gmap_protect_range()/gmap_sync_dirty_log_pmd() will not take the lock in case huge pages are not allowed.
gmap_protect_range() is called quite frequently for managing shadow page tables in vSIE environments.
Signed-off-by: David Hildenbrand <david@redhat.com> --- arch/s390/mm/gmap.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c index bb44990c8212..d4fa0a4514e0 100644 --- a/arch/s390/mm/gmap.c +++ b/arch/s390/mm/gmap.c @@ -905,10 +905,16 @@ static inline pmd_t *gmap_pmd_op_walk(struct gmap *gmap, unsigned long gaddr) pmd_t *pmdp; BUG_ON(gmap_is_shadow(gmap)); - spin_lock(&gmap->guest_table_lock); pmdp = (pmd_t *) gmap_table_walk(gmap, gaddr, 1); + if (!pmdp) + return NULL; - if (!pmdp || pmd_none(*pmdp)) { + /* without huge pages, there is no need to take the table lock */ + if (!gmap->mm->context.allow_gmap_hpage_1m) + return pmd_none(*pmdp) ? NULL : pmdp; + + spin_lock(&gmap->guest_table_lock); + if (pmd_none(*pmdp)) { spin_unlock(&gmap->guest_table_lock); return NULL; } -- 2.17.1
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