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From: Alexandre Ghiti <alexghiti@rivosinc.com>
To: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	linux-riscv@lists.infradead.org,
	linux-kernel@vger.kernel.org
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Subject: [PATCH] riscv: Only flush the mm icache when setting an exec pte
Date: Fri,  2 Feb 2024 13:47:11 +0100
Message-Id: <20240202124711.256146-1-alexghiti@rivosinc.com>
Precedence: bulk
MIME-Version: 1.0
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We used to emit a flush_icache_all() whenever a dirty executable
mapping is set in the page table but we can instead call
flush_icache_mm() which will only send IPIs to cores that currently run
this mm and add a deferred icache flush to the others.

The number of calls to sbi_remote_fence_i() (tested without IPI
support):

With a simple buildroot rootfs:
* Before: ~5k
* After :  4 (!)

Tested on HW, the boot to login is ~4.5% faster.

With an ubuntu rootfs:
* Before: ~24k
* After : ~13k

Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
---
 arch/riscv/include/asm/pgtable.h | 14 +++++++-------
 arch/riscv/mm/cacheflush.c       |  4 ++--
 arch/riscv/mm/pgtable.c          |  2 +-
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 0c94260b5d0c..058cfa89dd29 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -513,12 +513,12 @@ static inline void set_pte(pte_t *ptep, pte_t pteval)
 	WRITE_ONCE(*ptep, pteval);
 }
 
-void flush_icache_pte(pte_t pte);
+void flush_icache_pte(struct mm_struct *mm, pte_t pte);
 
-static inline void __set_pte_at(pte_t *ptep, pte_t pteval)
+static inline void __set_pte_at(struct mm_struct *mm, pte_t *ptep, pte_t pteval)
 {
 	if (pte_present(pteval) && pte_exec(pteval))
-		flush_icache_pte(pteval);
+		flush_icache_pte(mm, pteval);
 
 	set_pte(ptep, pteval);
 }
@@ -529,7 +529,7 @@ static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
 	page_table_check_ptes_set(mm, ptep, pteval, nr);
 
 	for (;;) {
-		__set_pte_at(ptep, pteval);
+		__set_pte_at(mm, ptep, pteval);
 		if (--nr == 0)
 			break;
 		ptep++;
@@ -541,7 +541,7 @@ static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
 static inline void pte_clear(struct mm_struct *mm,
 	unsigned long addr, pte_t *ptep)
 {
-	__set_pte_at(ptep, __pte(0));
+	__set_pte_at(mm, ptep, __pte(0));
 }
 
 #define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS	/* defined in mm/pgtable.c */
@@ -707,14 +707,14 @@ static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
 				pmd_t *pmdp, pmd_t pmd)
 {
 	page_table_check_pmd_set(mm, pmdp, pmd);
-	return __set_pte_at((pte_t *)pmdp, pmd_pte(pmd));
+	return __set_pte_at(mm, (pte_t *)pmdp, pmd_pte(pmd));
 }
 
 static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,
 				pud_t *pudp, pud_t pud)
 {
 	page_table_check_pud_set(mm, pudp, pud);
-	return __set_pte_at((pte_t *)pudp, pud_pte(pud));
+	return __set_pte_at(mm, (pte_t *)pudp, pud_pte(pud));
 }
 
 #ifdef CONFIG_PAGE_TABLE_CHECK
diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index b0774993c0f3..3e234e95d952 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -85,12 +85,12 @@ void flush_icache_mm(struct mm_struct *mm, bool local)
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_MMU
-void flush_icache_pte(pte_t pte)
+void flush_icache_pte(struct mm_struct *mm, pte_t pte)
 {
 	struct folio *folio = page_folio(pte_page(pte));
 
 	if (!test_bit(PG_dcache_clean, &folio->flags)) {
-		flush_icache_all();
+		flush_icache_mm(mm, false);
 		set_bit(PG_dcache_clean, &folio->flags);
 	}
 }
diff --git a/arch/riscv/mm/pgtable.c b/arch/riscv/mm/pgtable.c
index ef887efcb679..533ec9055fa0 100644
--- a/arch/riscv/mm/pgtable.c
+++ b/arch/riscv/mm/pgtable.c
@@ -10,7 +10,7 @@ int ptep_set_access_flags(struct vm_area_struct *vma,
 			  pte_t entry, int dirty)
 {
 	if (!pte_same(ptep_get(ptep), entry))
-		__set_pte_at(ptep, entry);
+		__set_pte_at(vma->vm_mm, ptep, entry);
 	/*
 	 * update_mmu_cache will unconditionally execute, handling both
 	 * the case that the PTE changed and the spurious fault case.
-- 
2.39.2