Re: [PATCH v1 3/5] s390/uv: convert PG_arch_1 users to only work on small folios

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On 10.04.24 19:42, Claudio Imbrenda wrote:
On Thu,  4 Apr 2024 18:36:40 +0200
David Hildenbrand <david@xxxxxxxxxx> wrote:

Now that make_folio_secure() may only set PG_arch_1 for small folios,
let's convert relevant remaining UV code to only work on (small) folios
and simply reject large folios early. This way, we'll never end up
touching PG_arch_1 on tail pages of a large folio in UV code.

The folio_get()/folio_put() for functions that are documented to already
hold a folio reference look weird and it should probably be removed.
Similarly, uv_destroy_owned_page() and uv_convert_owned_from_secure()
should really consume a folio reference instead. But these are cleanups for
another day.

Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
  arch/s390/include/asm/page.h |  1 +
  arch/s390/kernel/uv.c        | 39 +++++++++++++++++++++---------------
  2 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 54d015bcd8e3..b64384872c0f 100644
--- a/arch/s390/include/asm/page.h
+++ b/arch/s390/include/asm/page.h
@@ -214,6 +214,7 @@ static inline unsigned long __phys_addr(unsigned long x, bool is_31bit)
  #define pfn_to_phys(pfn)	((pfn) << PAGE_SHIFT)
#define phys_to_page(phys) pfn_to_page(phys_to_pfn(phys))
+#define phys_to_folio(phys)	page_folio(phys_to_page(phys))
  #define page_to_phys(page)	pfn_to_phys(page_to_pfn(page))
  #define folio_to_phys(page)	pfn_to_phys(folio_pfn(folio))
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index adcbd4b13035..9c0113b26735 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -134,14 +134,17 @@ static int uv_destroy_page(unsigned long paddr)
   */
  int uv_destroy_owned_page(unsigned long paddr)
  {
-	struct page *page = phys_to_page(paddr);
+	struct folio *folio = phys_to_folio(paddr);
  	int rc;
- get_page(page);
+	if (unlikely(folio_test_large(folio)))
+		return 0;

please add a comment here to explain why it's ok to just return 0
here...


Will use

"/* See gmap_make_secure(): large folios cannot be protected */"


+
+	folio_get(folio);
  	rc = uv_destroy_page(paddr);
  	if (!rc)
-		clear_bit(PG_arch_1, &page->flags);
-	put_page(page);
+		clear_bit(PG_arch_1, &folio->flags);
+	folio_put(folio);
  	return rc;
  }
@@ -169,14 +172,17 @@ int uv_convert_from_secure(unsigned long paddr)
   */
  int uv_convert_owned_from_secure(unsigned long paddr)
  {
-	struct page *page = phys_to_page(paddr);
+	struct folio *folio = phys_to_folio(paddr);
  	int rc;
- get_page(page);
+	if (unlikely(folio_test_large(folio)))
+		return 0;

... and here

here as well and ...


+
+	folio_get(folio);
  	rc = uv_convert_from_secure(paddr);
  	if (!rc)
-		clear_bit(PG_arch_1, &page->flags);
-	put_page(page);
+		clear_bit(PG_arch_1, &folio->flags);
+	folio_put(folio);
  	return rc;
  }
@@ -457,33 +463,34 @@ EXPORT_SYMBOL_GPL(gmap_destroy_page);
   */
  int arch_make_page_accessible(struct page *page)
  {
+	struct folio *folio = page_folio(page);
  	int rc = 0;
- /* Hugepage cannot be protected, so nothing to do */
-	if (PageHuge(page))
+	/* Large folios cannot be protected, so nothing to do */

^ here as well.

+	if (unlikely(folio_test_large(folio)))
  		return 0;

--
Cheers,

David / dhildenb





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