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[92.145.124.62]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-41f42e74625sm47255965e9.0.2024.05.08.12.23.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 May 2024 12:23:39 -0700 (PDT) From: Alexandre Ghiti To: Ryan Roberts , Catalin Marinas , Will Deacon , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Paul Walmsley , Palmer Dabbelt , Albert Ou , Ard Biesheuvel , Anup Patel , Atish Patra , Andrey Ryabinin , Andrey Konovalov , Vincenzo Frascino , Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-riscv@lists.infradead.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-mm@kvack.org Cc: Alexandre Ghiti Subject: [PATCH 04/12] mm, riscv, arm64: Use common ptep_get_lockless() function Date: Wed, 8 May 2024 21:19:23 +0200 Message-Id: <20240508191931.46060-5-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240508191931.46060-1-alexghiti@rivosinc.com> References: <20240508191931.46060-1-alexghiti@rivosinc.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Make riscv use the contpte aware ptep_get_lockless() function from arm64. Signed-off-by: Alexandre Ghiti --- arch/arm64/include/asm/pgtable.h | 11 +---- arch/arm64/mm/contpte.c | 57 -------------------------- arch/riscv/include/asm/pgtable.h | 2 + include/linux/contpte.h | 1 + mm/contpte.c | 69 ++++++++++++++++++++++++++++++++ 5 files changed, 73 insertions(+), 67 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index e85b3a052a02..8a0603257436 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1384,7 +1384,6 @@ extern void ptep_modify_prot_commit(struct vm_area_struct *vma, * where it is possible and makes sense to do so. The PTE_CONT bit is considered * a private implementation detail of the public ptep API (see below). */ -extern pte_t contpte_ptep_get_lockless(pte_t *orig_ptep); extern void contpte_clear_full_ptes(struct mm_struct *mm, unsigned long addr, pte_t *ptep, unsigned int nr, int full); extern pte_t contpte_get_and_clear_full_ptes(struct mm_struct *mm, @@ -1430,16 +1429,8 @@ static inline unsigned int pte_batch_hint(pte_t *ptep, pte_t pte) extern pte_t ptep_get(pte_t *ptep); #define ptep_get ptep_get +extern pte_t ptep_get_lockless(pte_t *ptep); #define ptep_get_lockless ptep_get_lockless -static inline pte_t ptep_get_lockless(pte_t *ptep) -{ - pte_t pte = __ptep_get(ptep); - - if (likely(!pte_valid_cont(pte))) - return pte; - - return contpte_ptep_get_lockless(ptep); -} static inline void set_pte(pte_t *ptep, pte_t pte) { diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c index e225e458856e..5e9e40145085 100644 --- a/arch/arm64/mm/contpte.c +++ b/arch/arm64/mm/contpte.c @@ -28,63 +28,6 @@ static void contpte_try_unfold_partial(struct mm_struct *mm, unsigned long addr, } } -pte_t contpte_ptep_get_lockless(pte_t *orig_ptep) -{ - /* - * The ptep_get_lockless() API requires us to read and return *orig_ptep - * so that it is self-consistent, without the PTL held, so we may be - * racing with other threads modifying the pte. Usually a READ_ONCE() - * would suffice, but for the contpte case, we also need to gather the - * access and dirty bits from across all ptes in the contiguous block, - * and we can't read all of those neighbouring ptes atomically, so any - * contiguous range may be unfolded/modified/refolded under our feet. - * Therefore we ensure we read a _consistent_ contpte range by checking - * that all ptes in the range are valid and have CONT_PTE set, that all - * pfns are contiguous and that all pgprots are the same (ignoring - * access/dirty). If we find a pte that is not consistent, then we must - * be racing with an update so start again. If the target pte does not - * have CONT_PTE set then that is considered consistent on its own - * because it is not part of a contpte range. - */ - - pgprot_t orig_prot; - unsigned long pfn; - pte_t orig_pte; - pgprot_t prot; - pte_t *ptep; - pte_t pte; - int i; - -retry: - orig_pte = __ptep_get(orig_ptep); - - if (!pte_valid_cont(orig_pte)) - return orig_pte; - - orig_prot = pte_pgprot(pte_mkold(pte_mkclean(orig_pte))); - ptep = arch_contpte_align_down(orig_ptep); - pfn = pte_pfn(orig_pte) - (orig_ptep - ptep); - - for (i = 0; i < CONT_PTES; i++, ptep++, pfn++) { - pte = __ptep_get(ptep); - prot = pte_pgprot(pte_mkold(pte_mkclean(pte))); - - if (!pte_valid_cont(pte) || - pte_pfn(pte) != pfn || - pgprot_val(prot) != pgprot_val(orig_prot)) - goto retry; - - if (pte_dirty(pte)) - orig_pte = pte_mkdirty(orig_pte); - - if (pte_young(pte)) - orig_pte = pte_mkyoung(orig_pte); - } - - return orig_pte; -} -EXPORT_SYMBOL_GPL(contpte_ptep_get_lockless); - void contpte_clear_full_ptes(struct mm_struct *mm, unsigned long addr, pte_t *ptep, unsigned int nr, int full) { diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index ebfe6b16529e..62cad1b974f1 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -785,6 +785,8 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma, extern pte_t ptep_get(pte_t *ptep); #define ptep_get ptep_get +extern pte_t ptep_get_lockless(pte_t *ptep); +#define ptep_get_lockless ptep_get_lockless extern void set_ptes(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pteval, unsigned int nr); #define set_ptes set_ptes diff --git a/include/linux/contpte.h b/include/linux/contpte.h index 54d10204e9af..01da4bfc3af6 100644 --- a/include/linux/contpte.h +++ b/include/linux/contpte.h @@ -8,6 +8,7 @@ * a private implementation detail of the public ptep API (see below). */ pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte); +pte_t contpte_ptep_get_lockless(pte_t *orig_ptep); void __contpte_try_fold(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte); void contpte_try_fold(struct mm_struct *mm, unsigned long addr, diff --git a/mm/contpte.c b/mm/contpte.c index 566745d7842f..060e0bc1a2a3 100644 --- a/mm/contpte.c +++ b/mm/contpte.c @@ -42,6 +42,7 @@ * - huge_ptep_clear_flush() * - ptep_get() * - set_ptes() + * - ptep_get_lockless() */ pte_t huge_ptep_get(pte_t *ptep) @@ -589,4 +590,72 @@ __always_inline void set_ptes(struct mm_struct *mm, unsigned long addr, contpte_set_ptes(mm, addr, ptep, pte, nr); } } + +pte_t contpte_ptep_get_lockless(pte_t *orig_ptep) +{ + /* + * The ptep_get_lockless() API requires us to read and return *orig_ptep + * so that it is self-consistent, without the PTL held, so we may be + * racing with other threads modifying the pte. Usually a READ_ONCE() + * would suffice, but for the contpte case, we also need to gather the + * access and dirty bits from across all ptes in the contiguous block, + * and we can't read all of those neighbouring ptes atomically, so any + * contiguous range may be unfolded/modified/refolded under our feet. + * Therefore we ensure we read a _consistent_ contpte range by checking + * that all ptes in the range are valid and have CONT_PTE set, that all + * pfns are contiguous and that all pgprots are the same (ignoring + * access/dirty). If we find a pte that is not consistent, then we must + * be racing with an update so start again. If the target pte does not + * have CONT_PTE set then that is considered consistent on its own + * because it is not part of a contpte range. + */ + + pgprot_t orig_prot; + unsigned long pfn; + pte_t orig_pte; + pgprot_t prot; + pte_t *ptep; + pte_t pte; + int i, ncontig; + +retry: + orig_pte = __ptep_get(orig_ptep); + + if (!pte_valid_cont(orig_pte)) + return orig_pte; + + orig_prot = pte_pgprot(pte_mkold(pte_mkclean(orig_pte))); + ptep = arch_contpte_align_down(orig_ptep); + ncontig = arch_contpte_get_num_contig(NULL, 0, ptep, 0, NULL); + pfn = pte_pfn(orig_pte) - (orig_ptep - ptep); + + for (i = 0; i < ncontig; i++, ptep++, pfn++) { + pte = __ptep_get(ptep); + prot = pte_pgprot(pte_mkold(pte_mkclean(pte))); + + if (!pte_valid_cont(pte) || + pte_pfn(pte) != pfn || + pgprot_val(prot) != pgprot_val(orig_prot)) + goto retry; + + if (pte_dirty(pte)) + orig_pte = pte_mkdirty(orig_pte); + + if (pte_young(pte)) + orig_pte = pte_mkyoung(orig_pte); + } + + return orig_pte; +} +EXPORT_SYMBOL_GPL(contpte_ptep_get_lockless); + +__always_inline pte_t ptep_get_lockless(pte_t *ptep) +{ + pte_t pte = __ptep_get(ptep); + + if (likely(!pte_valid_cont(pte))) + return pte; + + return contpte_ptep_get_lockless(ptep); +} #endif /* CONFIG_THP_CONTPTE */