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[92.145.124.62]) by smtp.gmail.com with ESMTPSA id v8-20020a5d59c8000000b0033af2a91b47sm7494000wry.70.2024.01.31.08.00.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Jan 2024 08:00:33 -0800 (PST) From: Alexandre Ghiti To: Catalin Marinas , Will Deacon , Thomas Bogendoerfer , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Paul Walmsley , Palmer Dabbelt , Albert Ou , Andrew Morton , Ved Shanbhogue , Matt Evans , Dylan Jhong , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-mm@kvack.org Cc: Alexandre Ghiti Subject: [PATCH RFC/RFT v2 1/4] riscv: Add ISA extension parsing for Svvptc Date: Wed, 31 Jan 2024 16:59:26 +0100 Message-Id: <20240131155929.169961-2-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240131155929.169961-1-alexghiti@rivosinc.com> References: <20240131155929.169961-1-alexghiti@rivosinc.com> Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Add support to parse the Svvptc string in the riscv,isa string. Signed-off-by: Alexandre Ghiti --- arch/riscv/include/asm/hwcap.h | 1 + arch/riscv/kernel/cpufeature.c | 1 + 2 files changed, 2 insertions(+) diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h index 5340f818746b..2e15192135fb 100644 --- a/arch/riscv/include/asm/hwcap.h +++ b/arch/riscv/include/asm/hwcap.h @@ -80,6 +80,7 @@ #define RISCV_ISA_EXT_ZFA 71 #define RISCV_ISA_EXT_ZTSO 72 #define RISCV_ISA_EXT_ZACAS 73 +#define RISCV_ISA_EXT_SVVPTC 74 #define RISCV_ISA_EXT_MAX 128 #define RISCV_ISA_EXT_INVALID U32_MAX diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index 89920f84d0a3..4a8f14bfa0f2 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -307,6 +307,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = { __RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL), __RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT), __RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT), + __RISCV_ISA_EXT_DATA(svvptc, RISCV_ISA_EXT_SVVPTC), }; 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[92.145.124.62]) by smtp.gmail.com with ESMTPSA id c17-20020a5d5291000000b0033ae4ba8ca0sm11407009wrv.82.2024.01.31.08.01.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Jan 2024 08:01:34 -0800 (PST) From: Alexandre Ghiti To: Catalin Marinas , Will Deacon , Thomas Bogendoerfer , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Paul Walmsley , Palmer Dabbelt , Albert Ou , Andrew Morton , Ved Shanbhogue , Matt Evans , Dylan Jhong , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-mm@kvack.org Cc: Alexandre Ghiti Subject: [PATCH RFC/RFT v2 2/4] dt-bindings: riscv: Add Svvptc ISA extension description Date: Wed, 31 Jan 2024 16:59:27 +0100 Message-Id: <20240131155929.169961-3-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240131155929.169961-1-alexghiti@rivosinc.com> References: <20240131155929.169961-1-alexghiti@rivosinc.com> Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Add description for the Svvptc ISA extension which was ratified recently. Signed-off-by: Alexandre Ghiti --- Documentation/devicetree/bindings/riscv/extensions.yaml | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml index 63d81dc895e5..59bf14d2c1eb 100644 --- a/Documentation/devicetree/bindings/riscv/extensions.yaml +++ b/Documentation/devicetree/bindings/riscv/extensions.yaml @@ -171,6 +171,13 @@ properties: memory types as ratified in the 20191213 version of the privileged ISA specification. + - const: svvptc + description: + The standard Svvptc supervisor-level extension for + address-translation cache behaviour with respect to invalid entries + as ratified in the XXXXXXXX version of the privileged ISA + specification. + - const: zacas description: | The Zacas extension for Atomic Compare-and-Swap (CAS) instructions From patchwork Wed Jan 31 15:59:28 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexandre Ghiti X-Patchwork-Id: 13539568 Received: from mail-ej1-f49.google.com (mail-ej1-f49.google.com [209.85.218.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4849012AAFA for ; 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[92.145.124.62]) by smtp.gmail.com with ESMTPSA id vh8-20020a170907d38800b00a3040040011sm180335ejc.45.2024.01.31.08.02.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Jan 2024 08:02:36 -0800 (PST) From: Alexandre Ghiti To: Catalin Marinas , Will Deacon , Thomas Bogendoerfer , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Paul Walmsley , Palmer Dabbelt , Albert Ou , Andrew Morton , Ved Shanbhogue , Matt Evans , Dylan Jhong , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-mm@kvack.org Cc: Alexandre Ghiti Subject: [PATCH RFC/RFT v2 3/4] riscv: Stop emitting preventive sfence.vma for new vmalloc mappings Date: Wed, 31 Jan 2024 16:59:28 +0100 Message-Id: <20240131155929.169961-4-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240131155929.169961-1-alexghiti@rivosinc.com> References: <20240131155929.169961-1-alexghiti@rivosinc.com> Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In 6.5, we removed the vmalloc fault path because that can't work (see [1] [2]). Then in order to make sure that new page table entries were seen by the page table walker, we had to preventively emit a sfence.vma on all harts [3] but this solution is very costly since it relies on IPI. And even there, we could end up in a loop of vmalloc faults if a vmalloc allocation is done in the IPI path (for example if it is traced, see [4]), which could result in a kernel stack overflow. Those preventive sfence.vma needed to be emitted because: - if the uarch caches invalid entries, the new mapping may not be observed by the page table walker and an invalidation may be needed. - if the uarch does not cache invalid entries, a reordered access could "miss" the new mapping and traps: in that case, we would actually only need to retry the access, no sfence.vma is required. So this patch removes those preventive sfence.vma and actually handles the possible (and unlikely) exceptions. And since the kernel stacks mappings lie in the vmalloc area, this handling must be done very early when the trap is taken, at the very beginning of handle_exception: this also rules out the vmalloc allocations in the fault path. Link: https://lore.kernel.org/linux-riscv/20230531093817.665799-1-bjorn@kernel.org/ [1] Link: https://lore.kernel.org/linux-riscv/20230801090927.2018653-1-dylan@andestech.com [2] Link: https://lore.kernel.org/linux-riscv/20230725132246.817726-1-alexghiti@rivosinc.com/ [3] Link: https://lore.kernel.org/lkml/20200508144043.13893-1-joro@8bytes.org/ [4] Signed-off-by: Alexandre Ghiti --- arch/riscv/include/asm/cacheflush.h | 18 +++++- arch/riscv/include/asm/thread_info.h | 5 ++ arch/riscv/kernel/asm-offsets.c | 5 ++ arch/riscv/kernel/entry.S | 84 ++++++++++++++++++++++++++++ arch/riscv/mm/init.c | 2 + 5 files changed, 113 insertions(+), 1 deletion(-) diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h index a129dac4521d..b0d631701757 100644 --- a/arch/riscv/include/asm/cacheflush.h +++ b/arch/riscv/include/asm/cacheflush.h @@ -37,7 +37,23 @@ static inline void flush_dcache_page(struct page *page) flush_icache_mm(vma->vm_mm, 0) #ifdef CONFIG_64BIT -#define flush_cache_vmap(start, end) flush_tlb_kernel_range(start, end) +extern u64 new_vmalloc[NR_CPUS / sizeof(u64) + 1]; +extern char _end[]; +#define flush_cache_vmap flush_cache_vmap +static inline void flush_cache_vmap(unsigned long start, unsigned long end) +{ + if (is_vmalloc_or_module_addr((void *)start)) { + int i; + + /* + * We don't care if concurrently a cpu resets this value since + * the only place this can happen is in handle_exception() where + * an sfence.vma is emitted. + */ + for (i = 0; i < ARRAY_SIZE(new_vmalloc); ++i) + new_vmalloc[i] = -1ULL; + } +} #define flush_cache_vmap_early(start, end) local_flush_tlb_kernel_range(start, end) #endif diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h index 5d473343634b..32631acdcdd4 100644 --- a/arch/riscv/include/asm/thread_info.h +++ b/arch/riscv/include/asm/thread_info.h @@ -60,6 +60,11 @@ struct thread_info { void *scs_base; void *scs_sp; #endif + /* + * Used in handle_exception() to save a0, a1 and a2 before knowing if we + * can access the kernel stack. + */ + unsigned long a0, a1, a2; }; #ifdef CONFIG_SHADOW_CALL_STACK diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c index a03129f40c46..939ddc0e3c6e 100644 --- a/arch/riscv/kernel/asm-offsets.c +++ b/arch/riscv/kernel/asm-offsets.c @@ -35,6 +35,8 @@ void asm_offsets(void) OFFSET(TASK_THREAD_S9, task_struct, thread.s[9]); OFFSET(TASK_THREAD_S10, task_struct, thread.s[10]); OFFSET(TASK_THREAD_S11, task_struct, thread.s[11]); + + OFFSET(TASK_TI_CPU, task_struct, thread_info.cpu); OFFSET(TASK_TI_FLAGS, task_struct, thread_info.flags); OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count); OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp); @@ -42,6 +44,9 @@ void asm_offsets(void) #ifdef CONFIG_SHADOW_CALL_STACK OFFSET(TASK_TI_SCS_SP, task_struct, thread_info.scs_sp); #endif + OFFSET(TASK_TI_A0, task_struct, thread_info.a0); + OFFSET(TASK_TI_A1, task_struct, thread_info.a1); + OFFSET(TASK_TI_A2, task_struct, thread_info.a2); OFFSET(TASK_TI_CPU_NUM, task_struct, thread_info.cpu); OFFSET(TASK_THREAD_F0, task_struct, thread.fstate.f[0]); diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index 9d1a305d5508..c1ffaeaba7aa 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -19,6 +19,78 @@ .section .irqentry.text, "ax" +.macro new_vmalloc_check + REG_S a0, TASK_TI_A0(tp) + REG_S a1, TASK_TI_A1(tp) + REG_S a2, TASK_TI_A2(tp) + + csrr a0, CSR_CAUSE + /* Exclude IRQs */ + blt a0, zero, _new_vmalloc_restore_context + /* Only check new_vmalloc if we are in page/protection fault */ + li a1, EXC_LOAD_PAGE_FAULT + beq a0, a1, _new_vmalloc_kernel_address + li a1, EXC_STORE_PAGE_FAULT + beq a0, a1, _new_vmalloc_kernel_address + li a1, EXC_INST_PAGE_FAULT + bne a0, a1, _new_vmalloc_restore_context + +_new_vmalloc_kernel_address: + /* Is it a kernel address? */ + csrr a0, CSR_TVAL + bge a0, zero, _new_vmalloc_restore_context + + /* Check if a new vmalloc mapping appeared that could explain the trap */ + + /* + * Computes: + * a0 = &new_vmalloc[BIT_WORD(cpu)] + * a1 = BIT_MASK(cpu) + */ + REG_L a2, TASK_TI_CPU(tp) + /* + * Compute the new_vmalloc element position: + * (cpu / 64) * 8 = (cpu >> 6) << 3 + */ + srli a1, a2, 6 + slli a1, a1, 3 + la a0, new_vmalloc + add a0, a0, a1 + /* + * Compute the bit position in the new_vmalloc element: + * bit_pos = cpu % 64 = cpu - (cpu / 64) * 64 = cpu - (cpu >> 6) << 6 + * = cpu - ((cpu >> 6) << 3) << 3 + */ + slli a1, a1, 3 + sub a1, a2, a1 + /* Compute the "get mask": 1 << bit_pos */ + li a2, 1 + sll a1, a2, a1 + + /* Check the value of new_vmalloc for this cpu */ + REG_L a2, 0(a0) + and a2, a2, a1 + beq a2, zero, _new_vmalloc_restore_context + + /* Atomically reset the current cpu bit in new_vmalloc */ + amoxor.w a0, a1, (a0) + + /* Only emit a sfence.vma if the uarch caches invalid entries */ + ALTERNATIVE("sfence.vma", "nop", 0, RISCV_ISA_EXT_SVVPTC, 1) + + REG_L a0, TASK_TI_A0(tp) + REG_L a1, TASK_TI_A1(tp) + REG_L a2, TASK_TI_A2(tp) + csrw CSR_SCRATCH, x0 + sret + +_new_vmalloc_restore_context: + REG_L a0, TASK_TI_A0(tp) + REG_L a1, TASK_TI_A1(tp) + REG_L a2, TASK_TI_A2(tp) +.endm + + SYM_CODE_START(handle_exception) /* * If coming from userspace, preserve the user thread pointer and load @@ -30,6 +102,18 @@ SYM_CODE_START(handle_exception) .Lrestore_kernel_tpsp: csrr tp, CSR_SCRATCH + + /* + * The RISC-V kernel does not eagerly emit a sfence.vma after each + * new vmalloc mapping, which may result in exceptions: + * - if the uarch caches invalid entries, the new mapping would not be + * observed by the page table walker and an invalidation is needed. + * - if the uarch does not cache invalid entries, a reordered access + * could "miss" the new mapping and traps: in that case, we only need + * to retry the access, no sfence.vma is required. + */ + new_vmalloc_check + REG_S sp, TASK_TI_KERNEL_SP(tp) #ifdef CONFIG_VMAP_STACK diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index eafc4c2200f2..54c9fdeda11e 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -36,6 +36,8 @@ #include "../kernel/head.h" +u64 new_vmalloc[NR_CPUS / sizeof(u64) + 1]; 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[92.145.124.62]) by smtp.gmail.com with ESMTPSA id bu16-20020a056000079000b0033b0797cc14sm1358024wrb.51.2024.01.31.08.03.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Jan 2024 08:03:37 -0800 (PST) From: Alexandre Ghiti To: Catalin Marinas , Will Deacon , Thomas Bogendoerfer , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Paul Walmsley , Palmer Dabbelt , Albert Ou , Andrew Morton , Ved Shanbhogue , Matt Evans , Dylan Jhong , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-mm@kvack.org Cc: Alexandre Ghiti Subject: [PATCH RFC/RFT v2 4/4] riscv: Stop emitting preventive sfence.vma for new userspace mappings with Svvptc Date: Wed, 31 Jan 2024 16:59:29 +0100 Message-Id: <20240131155929.169961-5-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240131155929.169961-1-alexghiti@rivosinc.com> References: <20240131155929.169961-1-alexghiti@rivosinc.com> Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 The preventive sfence.vma were emitted because new mappings must be made visible to the page table walker but Svvptc guarantees that xRET act as a fence, so no need to sfence.vma for the uarchs that implement this extension. This allows to drastically reduce the number of sfence.vma emitted: * Ubuntu boot to login: Before: ~630k sfence.vma After: ~200k sfence.vma * ltp - mmapstress01 Before: ~45k After: ~6.3k * lmbench - lat_pagefault Before: ~665k After: 832 (!) * lmbench - lat_mmap Before: ~546k After: 718 (!) Signed-off-by: Alexandre Ghiti --- arch/riscv/include/asm/pgtable.h | 16 +++++++++++++++- arch/riscv/mm/pgtable.c | 13 +++++++++++++ 2 files changed, 28 insertions(+), 1 deletion(-) diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index 0c94260b5d0c..50986e4c4601 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -473,6 +473,9 @@ static inline void update_mmu_cache_range(struct vm_fault *vmf, struct vm_area_struct *vma, unsigned long address, pte_t *ptep, unsigned int nr) { + asm_volatile_goto(ALTERNATIVE("nop", "j %l[svvptc]", 0, RISCV_ISA_EXT_SVVPTC, 1) + : : : : svvptc); + /* * The kernel assumes that TLBs don't cache invalid entries, but * in RISC-V, SFENCE.VMA specifies an ordering constraint, not a @@ -482,12 +485,23 @@ static inline void update_mmu_cache_range(struct vm_fault *vmf, */ while (nr--) local_flush_tlb_page(address + nr * PAGE_SIZE); + +svvptc: + /* + * Svvptc guarantees that xRET act as a fence, so when the uarch does + * not cache invalid entries, we don't have to do anything. + */ + ; } #define update_mmu_cache(vma, addr, ptep) \ update_mmu_cache_range(NULL, vma, addr, ptep, 1) #define __HAVE_ARCH_UPDATE_MMU_TLB -#define update_mmu_tlb update_mmu_cache +static inline void update_mmu_tlb(struct vm_area_struct *vma, + unsigned long address, pte_t *ptep) +{ + flush_tlb_range(vma, address, address + PAGE_SIZE); +} static inline void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long address, pmd_t *pmdp) diff --git a/arch/riscv/mm/pgtable.c b/arch/riscv/mm/pgtable.c index ef887efcb679..99ed389e4c8a 100644 --- a/arch/riscv/mm/pgtable.c +++ b/arch/riscv/mm/pgtable.c @@ -9,6 +9,9 @@ int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, pte_t *ptep, pte_t entry, int dirty) { + asm_volatile_goto(ALTERNATIVE("nop", "j %l[svvptc]", 0, RISCV_ISA_EXT_SVVPTC, 1) + : : : : svvptc); + if (!pte_same(ptep_get(ptep), entry)) __set_pte_at(ptep, entry); /* @@ -16,6 +19,16 @@ int ptep_set_access_flags(struct vm_area_struct *vma, * the case that the PTE changed and the spurious fault case. */ return true; + +svvptc: + if (!pte_same(ptep_get(ptep), entry)) { + __set_pte_at(ptep, entry); + /* Here only not svadu is impacted */ + flush_tlb_page(vma, address); + return true; + } + + return false; } int ptep_test_and_clear_young(struct vm_area_struct *vma,