linux-kernel - [PATCH v1 3/4] sparc/mm: Avoid calling arch_enter/leave_lazy_mmu() in set

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Message-ID: <20250302145555.3236789-4-ryan.roberts@arm.com>
Date: Sun,  2 Mar 2025 14:55:53 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Andreas Larsson <andreas@...sler.com>,
	Juergen Gross <jgross@...e.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Catalin Marinas <catalin.marinas@....com>
Cc: Ryan Roberts <ryan.roberts@....com>,
	linux-mm@...ck.org,
	sparclinux@...r.kernel.org,
	xen-devel@...ts.xenproject.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v1 3/4] sparc/mm: Avoid calling arch_enter/leave_lazy_mmu() in set_ptes

With commit 1a10a44dfc1d ("sparc64: implement the new page table range
API") set_ptes was added to the sparc architecture. The implementation
included calling arch_enter/leave_lazy_mmu() calls.

The patch removes the usage of arch_enter/leave_lazy_mmu() since this
implies nesting of lazy mmu regions which is not supported. Without this
fix, lazy mmu mode is effectively disabled because we exit the mode
after the first set_ptes:

remap_pte_range()
  -> arch_enter_lazy_mmu()
  -> set_ptes()
      -> arch_enter_lazy_mmu()
      -> arch_leave_lazy_mmu()
  -> arch_leave_lazy_mmu()

Powerpc suffered the same problem and fixed it in a corresponding way
with commit 47b8def9358c ("powerpc/mm: Avoid calling
arch_enter/leave_lazy_mmu() in set_ptes").

Fixes: 1a10a44dfc1d ("sparc64: implement the new page table range API")
Signed-off-by: Ryan Roberts <ryan.roberts@....com>
---
 arch/sparc/include/asm/pgtable_64.h | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 2b7f358762c1..dc28f2c4eee3 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -936,7 +936,6 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
 		pte_t *ptep, pte_t pte, unsigned int nr)
 {
-	arch_enter_lazy_mmu_mode();
 	for (;;) {
 		__set_pte_at(mm, addr, ptep, pte, 0);
 		if (--nr == 0)
@@ -945,7 +944,6 @@ static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
 		pte_val(pte) += PAGE_SIZE;
 		addr += PAGE_SIZE;
 	}
-	arch_leave_lazy_mmu_mode();
 }
 #define set_ptes set_ptes
 
-- 
2.43.0