Received-SPF: pass (google.com: domain of linux-kernel+bounces-121500-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
From: peterx@redhat.com
To: linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Cc: Yang Shi <shy828301@gmail.com>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	John Hubbard <jhubbard@nvidia.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	peterx@redhat.com,
	Andrew Jones <andrew.jones@linux.dev>,
	Muchun Song <muchun.song@linux.dev>,
	linux-riscv@lists.infradead.org,
	linuxppc-dev@lists.ozlabs.org,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Andrew Morton <akpm@linux-foundation.org>,
	Christoph Hellwig <hch@infradead.org>,
	Lorenzo Stoakes <lstoakes@gmail.com>,
	Matthew Wilcox <willy@infradead.org>,
	Rik van Riel <riel@surriel.com>,
	linux-arm-kernel@lists.infradead.org,
	Andrea Arcangeli <aarcange@redhat.com>,
	David Hildenbrand <david@redhat.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	James Houghton <jthoughton@google.com>,
	Jason Gunthorpe <jgg@nvidia.com>,
	Mike Rapoport <rppt@kernel.org>,
	Axel Rasmussen <axelrasmussen@google.com>
Subject: [PATCH v4 05/13] mm/arch: Provide pud_pfn() fallback
Date: Wed, 27 Mar 2024 11:23:24 -0400
Message-ID: <20240327152332.950956-6-peterx@redhat.com>
In-Reply-To: <20240327152332.950956-1-peterx@redhat.com>
References: <20240327152332.950956-1-peterx@redhat.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

From: Peter Xu <peterx@redhat.com>

The comment in the code explains the reasons.  We took a different approach
comparing to pmd_pfn() by providing a fallback function.

Another option is to provide some lower level config options (compare to
HUGETLB_PAGE or THP) to identify which layer an arch can support for such
huge mappings.  However that can be an overkill.

Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 arch/riscv/include/asm/pgtable.h    |  1 +
 arch/s390/include/asm/pgtable.h     |  1 +
 arch/sparc/include/asm/pgtable_64.h |  1 +
 arch/x86/include/asm/pgtable.h      |  1 +
 include/linux/pgtable.h             | 10 ++++++++++
 5 files changed, 14 insertions(+)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 20242402fc11..0ca28cc8e3fa 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -646,6 +646,7 @@ static inline unsigned long pmd_pfn(pmd_t pmd)
 
 #define __pud_to_phys(pud)  (__page_val_to_pfn(pud_val(pud)) << PAGE_SHIFT)
 
+#define pud_pfn pud_pfn
 static inline unsigned long pud_pfn(pud_t pud)
 {
 	return ((__pud_to_phys(pud) & PUD_MASK) >> PAGE_SHIFT);
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 1a71cb19c089..6cbbe473f680 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1414,6 +1414,7 @@ static inline unsigned long pud_deref(pud_t pud)
 	return (unsigned long)__va(pud_val(pud) & origin_mask);
 }
 
+#define pud_pfn pud_pfn
 static inline unsigned long pud_pfn(pud_t pud)
 {
 	return __pa(pud_deref(pud)) >> PAGE_SHIFT;
diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 4d1bafaba942..26efc9bb644a 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -875,6 +875,7 @@ static inline bool pud_leaf(pud_t pud)
 	return pte_val(pte) & _PAGE_PMD_HUGE;
 }
 
+#define pud_pfn pud_pfn
 static inline unsigned long pud_pfn(pud_t pud)
 {
 	pte_t pte = __pte(pud_val(pud));
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index cefc7a84f7a4..273f7557218c 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -234,6 +234,7 @@ static inline unsigned long pmd_pfn(pmd_t pmd)
 	return (pfn & pmd_pfn_mask(pmd)) >> PAGE_SHIFT;
 }
 
+#define pud_pfn pud_pfn
 static inline unsigned long pud_pfn(pud_t pud)
 {
 	phys_addr_t pfn = pud_val(pud);
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 600e17d03659..75fe309a4e10 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1817,6 +1817,16 @@ typedef unsigned int pgtbl_mod_mask;
 #define pte_leaf_size(x) PAGE_SIZE
 #endif
 
+/*
+ * We always define pmd_pfn for all archs as it's used in lots of generic
+ * code.  Now it happens too for pud_pfn (and can happen for larger
+ * mappings too in the future; we're not there yet).  Instead of defining
+ * it for all archs (like pmd_pfn), provide a fallback.
+ */
+#ifndef pud_pfn
+#define pud_pfn(x) ({ BUILD_BUG(); 0; })
+#endif
+
 /*
  * Some architectures have MMUs that are configurable or selectable at boot
  * time. These lead to variable PTRS_PER_x. For statically allocated arrays it
-- 
2.44.0