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s390/uv: convert gmap_destroy_page() from follow_page() to folio_walk

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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.

Link: https://lkml.kernel.org/r/20240802155524.517137-9-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2024-08-02 17:55:21 +02:00 committed by Andrew Morton
parent 8710f6ed34
commit 85a7e5432d
1 changed files with 12 additions and 6 deletions
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18
arch/s390/kernel/uv.c
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@ -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;