From: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
With the introduction of protected KVM guests on s390 there is now a
concept of inaccessible pages. These pages need to be made accessible
before the host can access them.
While cpu accesses will trigger a fault that can be resolved, I/O
accesses will just fail. We need to add a callback into architecture
code for places that will do I/Oi, namely when writeback is started or
when a page reference is taken.
Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
---
include/linux/gfp.h | 6 ++++++
mm/gup.c | 2 ++
mm/page-writeback.c | 1 +
3 files changed, 9 insertions(+)
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index e5b817cb86e7..be2754841369 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -485,6 +485,12 @@ static inline void arch_free_page(struct page *page, int order) { }
#ifndef HAVE_ARCH_ALLOC_PAGE
static inline void arch_alloc_page(struct page *page, int order) { }
#endif
+#ifndef HAVE_ARCH_MAKE_PAGE_ACCESSIBLE
+static inline int arch_make_page_accessible(struct page *page)
+{
+ return 0;
+}
+#endif
struct page *
__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
diff --git a/mm/gup.c b/mm/gup.c
index 7646bf993b25..a01262cd2821 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -257,6 +257,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
page = ERR_PTR(-ENOMEM);
goto out;
}
+ arch_make_page_accessible(page);
}
if (flags & FOLL_TOUCH) {
if ((flags & FOLL_WRITE) &&
@@ -1870,6 +1871,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
VM_BUG_ON_PAGE(compound_head(page) != head, page);
+ arch_make_page_accessible(page);
SetPageReferenced(page);
pages[*nr] = page;
(*nr)++;
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 2caf780a42e7..0f0bd14571b1 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2806,6 +2806,7 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
inc_lruvec_page_state(page, NR_WRITEBACK);
inc_zone_page_state(page, NR_ZONE_WRITE_PENDING);
}
+ arch_make_page_accessible(page);
unlock_page_memcg(page);
return ret;
--
2.24.0
