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Message-Id: <20250310132222.58378-3-luxu.kernel@bytedance.com>
Date: Mon, 10 Mar 2025 21:22:20 +0800
From: Xu Lu <luxu.kernel@...edance.com>
To: akpm@...ux-foundation.org,
	tjeznach@...osinc.com,
	joro@...tes.org,
	will@...nel.org,
	robin.murphy@....com
Cc: lihangjing@...edance.com,
	xieyongji@...edance.com,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Xu Lu <luxu.kernel@...edance.com>
Subject: [PATCH 2/4] iommu/riscv: Use pte_t to represent page table entry

Since RISC-V IOMMU has the same pte format and translation process with
MMU as is specified in RISC-V Privileged specification, we use pte_t to
represent IOMMU pte too to reuse existing pte operation functions.

Signed-off-by: Xu Lu <luxu.kernel@...edance.com>
---
 drivers/iommu/riscv/iommu.c | 66 ++++++++++++++++++-------------------
 1 file changed, 33 insertions(+), 33 deletions(-)

diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
index 8f049d4a0e2cb..f752096989a79 100644
--- a/drivers/iommu/riscv/iommu.c
+++ b/drivers/iommu/riscv/iommu.c
@@ -812,7 +812,7 @@ struct riscv_iommu_domain {
 	bool amo_enabled;
 	int numa_node;
 	unsigned int pgd_mode;
-	unsigned long *pgd_root;
+	pte_t *pgd_root;
 };
 
 #define iommu_domain_to_riscv(iommu_domain) \
@@ -1081,27 +1081,29 @@ static void riscv_iommu_iotlb_sync(struct iommu_domain *iommu_domain,
 
 #define PT_SHIFT (PAGE_SHIFT - ilog2(sizeof(pte_t)))
 
-#define _io_pte_present(pte)	((pte) & (_PAGE_PRESENT | _PAGE_PROT_NONE))
-#define _io_pte_leaf(pte)	((pte) & _PAGE_LEAF)
-#define _io_pte_none(pte)	((pte) == 0)
-#define _io_pte_entry(pn, prot)	((_PAGE_PFN_MASK & ((pn) << _PAGE_PFN_SHIFT)) | (prot))
+#define _io_pte_present(pte)	(pte_val(pte) & (_PAGE_PRESENT | _PAGE_PROT_NONE))
+#define _io_pte_leaf(pte)	(pte_val(pte) & _PAGE_LEAF)
+#define _io_pte_none(pte)	(pte_val(pte) == 0)
+#define _io_pte_entry(pn, prot)	(__pte((_PAGE_PFN_MASK & ((pn) << _PAGE_PFN_SHIFT)) | (prot)))
 
 static void riscv_iommu_pte_free(struct riscv_iommu_domain *domain,
-				 unsigned long pte, struct list_head *freelist)
+				 pte_t pte, struct list_head *freelist)
 {
-	unsigned long *ptr;
+	pte_t *ptr;
 	int i;
 
 	if (!_io_pte_present(pte) || _io_pte_leaf(pte))
 		return;
 
-	ptr = (unsigned long *)pfn_to_virt(__page_val_to_pfn(pte));
+	ptr = (pte_t *)pfn_to_virt(pte_pfn(pte));
 
 	/* Recursively free all sub page table pages */
 	for (i = 0; i < PTRS_PER_PTE; i++) {
-		pte = READ_ONCE(ptr[i]);
-		if (!_io_pte_none(pte) && cmpxchg_relaxed(ptr + i, pte, 0) == pte)
+		pte = ptr[i];
+		if (!_io_pte_none(pte)) {
+			ptr[i] = __pte(0);
 			riscv_iommu_pte_free(domain, pte, freelist);
+		}
 	}
 
 	if (freelist)
@@ -1110,12 +1112,12 @@ static void riscv_iommu_pte_free(struct riscv_iommu_domain *domain,
 		iommu_free_page(ptr);
 }
 
-static unsigned long *riscv_iommu_pte_alloc(struct riscv_iommu_domain *domain,
+static pte_t *riscv_iommu_pte_alloc(struct riscv_iommu_domain *domain,
 					    unsigned long iova, size_t pgsize,
 					    gfp_t gfp)
 {
-	unsigned long *ptr = domain->pgd_root;
-	unsigned long pte, old;
+	pte_t *ptr = domain->pgd_root;
+	pte_t pte, old;
 	int level = domain->pgd_mode - RISCV_IOMMU_DC_FSC_IOSATP_MODE_SV39 + 2;
 	void *addr;
 
@@ -1131,7 +1133,7 @@ static unsigned long *riscv_iommu_pte_alloc(struct riscv_iommu_domain *domain,
 		if (((size_t)1 << shift) == pgsize)
 			return ptr;
 pte_retry:
-		pte = READ_ONCE(*ptr);
+		pte = ptep_get(ptr);
 		/*
 		 * This is very likely incorrect as we should not be adding
 		 * new mapping with smaller granularity on top
@@ -1154,31 +1156,31 @@ static unsigned long *riscv_iommu_pte_alloc(struct riscv_iommu_domain *domain,
 				goto pte_retry;
 			}
 		}
-		ptr = (unsigned long *)pfn_to_virt(__page_val_to_pfn(pte));
+		ptr = (pte_t *)pfn_to_virt(pte_pfn(pte));
 	} while (level-- > 0);
 
 	return NULL;
 }
 
-static unsigned long *riscv_iommu_pte_fetch(struct riscv_iommu_domain *domain,
-					    unsigned long iova, size_t *pte_pgsize)
+static pte_t *riscv_iommu_pte_fetch(struct riscv_iommu_domain *domain,
+				    unsigned long iova, size_t *pte_pgsize)
 {
-	unsigned long *ptr = domain->pgd_root;
-	unsigned long pte;
+	pte_t *ptr = domain->pgd_root;
+	pte_t pte;
 	int level = domain->pgd_mode - RISCV_IOMMU_DC_FSC_IOSATP_MODE_SV39 + 2;
 
 	do {
 		const int shift = PAGE_SHIFT + PT_SHIFT * level;
 
 		ptr += ((iova >> shift) & (PTRS_PER_PTE - 1));
-		pte = READ_ONCE(*ptr);
+		pte = ptep_get(ptr);
 		if (_io_pte_present(pte) && _io_pte_leaf(pte)) {
 			*pte_pgsize = (size_t)1 << shift;
 			return ptr;
 		}
 		if (_io_pte_none(pte))
 			return NULL;
-		ptr = (unsigned long *)pfn_to_virt(__page_val_to_pfn(pte));
+		ptr = (pte_t *)pfn_to_virt(pte_pfn(pte));
 	} while (level-- > 0);
 
 	return NULL;
@@ -1191,8 +1193,9 @@ static int riscv_iommu_map_pages(struct iommu_domain *iommu_domain,
 {
 	struct riscv_iommu_domain *domain = iommu_domain_to_riscv(iommu_domain);
 	size_t size = 0;
-	unsigned long *ptr;
-	unsigned long pte, old, pte_prot;
+	pte_t *ptr;
+	pte_t pte, old;
+	unsigned long pte_prot;
 	int rc = 0;
 	LIST_HEAD(freelist);
 
@@ -1210,10 +1213,9 @@ static int riscv_iommu_map_pages(struct iommu_domain *iommu_domain,
 			break;
 		}
 
-		old = READ_ONCE(*ptr);
+		old = ptep_get(ptr);
 		pte = _io_pte_entry(phys_to_pfn(phys), pte_prot);
-		if (cmpxchg_relaxed(ptr, old, pte) != old)
-			continue;
+		set_pte(ptr, pte);
 
 		riscv_iommu_pte_free(domain, old, &freelist);
 
@@ -1247,7 +1249,7 @@ static size_t riscv_iommu_unmap_pages(struct iommu_domain *iommu_domain,
 {
 	struct riscv_iommu_domain *domain = iommu_domain_to_riscv(iommu_domain);
 	size_t size = pgcount << __ffs(pgsize);
-	unsigned long *ptr, old;
+	pte_t *ptr;
 	size_t unmapped = 0;
 	size_t pte_size;
 
@@ -1260,9 +1262,7 @@ static size_t riscv_iommu_unmap_pages(struct iommu_domain *iommu_domain,
 		if (iova & (pte_size - 1))
 			return unmapped;
 
-		old = READ_ONCE(*ptr);
-		if (cmpxchg_relaxed(ptr, old, 0) != old)
-			continue;
+		set_pte(ptr, __pte(0));
 
 		iommu_iotlb_gather_add_page(&domain->domain, gather, iova,
 					    pte_size);
@@ -1279,13 +1279,13 @@ static phys_addr_t riscv_iommu_iova_to_phys(struct iommu_domain *iommu_domain,
 {
 	struct riscv_iommu_domain *domain = iommu_domain_to_riscv(iommu_domain);
 	size_t pte_size;
-	unsigned long *ptr;
+	pte_t *ptr;
 
 	ptr = riscv_iommu_pte_fetch(domain, iova, &pte_size);
-	if (_io_pte_none(*ptr) || !_io_pte_present(*ptr))
+	if (_io_pte_none(ptep_get(ptr)) || !_io_pte_present(ptep_get(ptr)))
 		return 0;
 
-	return pfn_to_phys(__page_val_to_pfn(*ptr)) | (iova & (pte_size - 1));
+	return pfn_to_phys(pte_pfn(ptep_get(ptr))) | (iova & (pte_size - 1));
 }
 
 static void riscv_iommu_free_paging_domain(struct iommu_domain *iommu_domain)
-- 
2.20.1


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