| Message ID | 20240802155524.517137-9-david@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: replace follow_page() by folio_walk | expand |
On Fri, 2 Aug 2024 17:55:21 +0200 David Hildenbrand <david@redhat.com> wrote: > Let's get rid of another follow_page() user and perform the UV calls > under PTL -- which likely should be fine. > > No need for an additional reference while holding the PTL: > uv_destroy_folio() and uv_convert_from_secure_folio() raise the > refcount, so any concurrent make_folio_secure() would see an unexpted > reference and cannot set PG_arch_1 concurrently. > > Do we really need a writable PTE? Likely yes, because the "destroy" > part is, in comparison to the export, a destructive operation. So we'll > keep the writability check for now. > > We'll lose the secretmem check from follow_page(). Likely we don't care > about that here. > > Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com> > --- > arch/s390/kernel/uv.c | 18 ++++++++++++------ > 1 file changed, 12 insertions(+), 6 deletions(-) > > diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c > index 35ed2aea8891..9646f773208a 100644 > --- a/arch/s390/kernel/uv.c > +++ b/arch/s390/kernel/uv.c > @@ -14,6 +14,7 @@ > #include <linux/memblock.h> > #include <linux/pagemap.h> > #include <linux/swap.h> > +#include <linux/pagewalk.h> > #include <asm/facility.h> > #include <asm/sections.h> > #include <asm/uv.h> > @@ -462,9 +463,9 @@ EXPORT_SYMBOL_GPL(gmap_convert_to_secure); > int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr) > { > struct vm_area_struct *vma; > + struct folio_walk fw; > unsigned long uaddr; > struct folio *folio; > - struct page *page; > int rc; > > rc = -EFAULT; > @@ -483,11 +484,15 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr) > goto out; > > rc = 0; > - /* we take an extra reference here */ > - page = follow_page(vma, uaddr, FOLL_WRITE | FOLL_GET); > - if (IS_ERR_OR_NULL(page)) > + folio = folio_walk_start(&fw, vma, uaddr, 0); > + if (!folio) > goto out; > - folio = page_folio(page); > + /* > + * See gmap_make_secure(): large folios cannot be secure. Small > + * folio implies FW_LEVEL_PTE. > + */ > + if (folio_test_large(folio) || !pte_write(fw.pte)) > + goto out_walk_end; > rc = uv_destroy_folio(folio); > /* > * Fault handlers can race; it is possible that two CPUs will fault > @@ -500,7 +505,8 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr) > */ > if (rc) > rc = uv_convert_from_secure_folio(folio); > - folio_put(folio); > +out_walk_end: > + folio_walk_end(&fw, vma); > out: > mmap_read_unlock(gmap->mm); > return rc;
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c index 35ed2aea8891..9646f773208a 100644 --- a/arch/s390/kernel/uv.c +++ b/arch/s390/kernel/uv.c @@ -14,6 +14,7 @@ #include <linux/memblock.h> #include <linux/pagemap.h> #include <linux/swap.h> +#include <linux/pagewalk.h> #include <asm/facility.h> #include <asm/sections.h> #include <asm/uv.h> @@ -462,9 +463,9 @@ EXPORT_SYMBOL_GPL(gmap_convert_to_secure); int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr) { struct vm_area_struct *vma; + struct folio_walk fw; unsigned long uaddr; struct folio *folio; - struct page *page; int rc; rc = -EFAULT; @@ -483,11 +484,15 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr) goto out; rc = 0; - /* we take an extra reference here */ - page = follow_page(vma, uaddr, FOLL_WRITE | FOLL_GET); - if (IS_ERR_OR_NULL(page)) + folio = folio_walk_start(&fw, vma, uaddr, 0); + if (!folio) goto out; - folio = page_folio(page); + /* + * See gmap_make_secure(): large folios cannot be secure. Small + * folio implies FW_LEVEL_PTE. + */ + if (folio_test_large(folio) || !pte_write(fw.pte)) + goto out_walk_end; rc = uv_destroy_folio(folio); /* * Fault handlers can race; it is possible that two CPUs will fault @@ -500,7 +505,8 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr) */ if (rc) rc = uv_convert_from_secure_folio(folio); - folio_put(folio); +out_walk_end: + folio_walk_end(&fw, vma); out: mmap_read_unlock(gmap->mm); return rc;
Let's get rid of another follow_page() user and perform the UV calls under PTL -- which likely should be fine. No need for an additional reference while holding the PTL: uv_destroy_folio() and uv_convert_from_secure_folio() raise the refcount, so any concurrent make_folio_secure() would see an unexpted reference and cannot set PG_arch_1 concurrently. Do we really need a writable PTE? Likely yes, because the "destroy" part is, in comparison to the export, a destructive operation. So we'll keep the writability check for now. We'll lose the secretmem check from follow_page(). Likely we don't care about that here. Signed-off-by: David Hildenbrand <david@redhat.com> --- arch/s390/kernel/uv.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-)