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

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Date: Thu,  4 Apr 2024 18:36:40 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	linux-s390@...r.kernel.org,
	kvm@...r.kernel.org,
	David Hildenbrand <david@...hat.com>,
	Matthew Wilcox <willy@...radead.org>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Janosch Frank <frankja@...ux.ibm.com>,
	Claudio Imbrenda <imbrenda@...ux.ibm.com>,
	Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
	Thomas Huth <thuth@...hat.com>
Subject: [PATCH v1 3/5] s390/uv: convert PG_arch_1 users to only work on small folios

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@...hat.com>
---
 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;
+
+	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;
+
+	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 */
+	if (unlikely(folio_test_large(folio)))
 		return 0;
 
 	/*
 	 * PG_arch_1 is used in 3 places:
 	 * 1. for kernel page tables during early boot
 	 * 2. for storage keys of huge pages and KVM
-	 * 3. As an indication that this page might be secure. This can
+	 * 3. As an indication that this small folio might be secure. This can
 	 *    overindicate, e.g. we set the bit before calling
 	 *    convert_to_secure.
 	 * As secure pages are never huge, all 3 variants can co-exists.
 	 */
-	if (!test_bit(PG_arch_1, &page->flags))
+	if (!test_bit(PG_arch_1, &folio->flags))
 		return 0;
 
-	rc = uv_pin_shared(page_to_phys(page));
+	rc = uv_pin_shared(folio_to_phys(folio));
 	if (!rc) {
-		clear_bit(PG_arch_1, &page->flags);
+		clear_bit(PG_arch_1, &folio->flags);
 		return 0;
 	}
 
-	rc = uv_convert_from_secure(page_to_phys(page));
+	rc = uv_convert_from_secure(folio_to_phys(folio));
 	if (!rc) {
-		clear_bit(PG_arch_1, &page->flags);
+		clear_bit(PG_arch_1, &folio->flags);
 		return 0;
 	}
 
-- 
2.44.0