From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 72EC6C4708F for ; Sun, 30 May 2021 00:39:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3B0AF61152 for ; Sun, 30 May 2021 00:39:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229590AbhE3AlR (ORCPT ); Sat, 29 May 2021 20:41:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:56752 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229546AbhE3AlR (ORCPT ); Sat, 29 May 2021 20:41:17 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1CCB461107; Sun, 30 May 2021 00:39:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622335180; bh=zz/QLlDkmcV46YG1G4nPrmU4gw/ajU0Q456WlxmIpsQ=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=FRnl9qol1Fl9+NcwJZNvYDe2LmPLX7eLccJIZMFhkcEm7MS7oD2VefYxb7UQuR+mp Fa8VbWtq1A22AyDDg8zNO/rkGAQWYJd8/rICl5FYAd6upnjoxZSV/YStnyHtApbulj MegekhUaQgrrh33W9SQjJT9RchLHEakj6GBqTDVH9anfIOYJL3IlXEI8i8eTR/jCfl 00NjTn2Az+z5rX614BkgdHDu7NuNRvNwDMDI20MjhzzgmDiZsHm+PtQWZZT2Hfspv2 G2cXU6u7gHtQSO70rekzF7BWSiO774hKRDTfUfU87UbJiFuWDQaCVzHZhe1SlKveA0 Y+yYQX2HN7w9Q== Received: by mail-lj1-f182.google.com with SMTP id f12so10111348ljp.2; Sat, 29 May 2021 17:39:40 -0700 (PDT) X-Gm-Message-State: AOAM530tbWh06JgB9EmMrYsVP6pxg0BuCQ+Y8FZlXgkvtBSk/YSHaR5z 9QCfXPzXvyCqvP5zkHdXGVnTvdTURr8B/OWliKg= X-Google-Smtp-Source: ABdhPJza3/ltlanrLtzL4ty58q8ry4OB11PrKcmfQSEjJ+wlhiaMJ/v7AqzRPrzMJY97GcBxSjLWfA9zOGpPxXvrAcs= X-Received: by 2002:a05:651c:2d0:: with SMTP id f16mr3881029ljo.18.1622335178437; Sat, 29 May 2021 17:39:38 -0700 (PDT) MIME-Version: 1.0 References: <1622008161-41451-1-git-send-email-guoren@kernel.org> <1622008161-41451-3-git-send-email-guoren@kernel.org> <20210527070903.GA32653@lst.de> In-Reply-To: <20210527070903.GA32653@lst.de> From: Guo Ren Date: Sun, 30 May 2021 08:39:27 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH V4 2/2] riscv: Use use_asid_allocator flush TLB To: Christoph Hellwig Cc: Anup Patel , Palmer Dabbelt , Arnd Bergmann , linux-riscv , Linux Kernel Mailing List , linux-arch , linux-sunxi@lists.linux.dev, Guo Ren Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Thu, May 27, 2021 at 3:09 PM Christoph Hellwig wrote: > > On Wed, May 26, 2021 at 05:49:21AM +0000, guoren@kernel.org wrote: > > From: Guo Ren > > > > Use static_branch_unlikely(&use_asid_allocator) to keep the origin > > tlb flush style, so it's no effect on the existing machine. Here > > are the optimized functions: > > - flush_tlb_mm > > - flush_tlb_page > > - flush_tlb_range > > > > All above are based on the below new implement functions: > > - __sbi_tlb_flush_range_asid > > - local_flush_tlb_range_asid > > > > These functions are based on ASID instead of previous non-ASID > > tlb_flush implementation which invalidates more useful tlb > > entries. > > I still think the commit message is incomplete and rather misleading. > Here is what I'd come up with from reading the patch: > > --------- > Subject: add ASID-based tlbflushing methods > > Implement optimized version of the tlb flushing routines for systems > using ASIDs. These are behind the use_asid_allocator static branch to > not affect existing systems not using ASIDs. > --------- > > > > +static inline void local_flush_tlb_range_asid(unsigned long start, > > + unsigned long size, unsigned long asid) > > +{ > > + unsigned long tmp, end = ALIGN(start + size, PAGE_SIZE); > > + > > + for (tmp = start & PAGE_MASK; tmp < end; tmp += PAGE_SIZE) { > > + __asm__ __volatile__ ("sfence.vma %0, %1" > > + : > > + : "r" (tmp), "r" (asid) > > + : "memory"); > > + tmp += PAGE_SIZE; > > + } > > This double increments tmp. Yes, It's a bug for PATCH V4. Thx for point it out. > > Also the non-ASID code switches to a global flush once flushing more > than a single page. It might be worth documenting the tradeoff in the > code. > > > +static void __sbi_tlb_flush_range_asid(struct cpumask *cmask, > > + unsigned long start, > > + unsigned long size, > > + unsigned long asid) > > +{ > > I don't think the calling conventions here are optimal. I'd pass > the mm_struct as the first argument, as we can derive both the cpumask > and asid from it instead of doing that in the callers. > > But more importantly I think the static branch check can be moved deeper > into the code to avoid a lot of duplication. What do you think of this > version? Good idea, but I think "Modifying infrastructure and Adding ASID TLB flush" should be separated. I'll try in the next PATCH version. > > diff --git a/arch/riscv/include/asm/mmu_context.h b/arch/riscv/include/asm/mmu_context.h > index b0659413a080..7030837adc1a 100644 > --- a/arch/riscv/include/asm/mmu_context.h > +++ b/arch/riscv/include/asm/mmu_context.h > @@ -33,6 +33,8 @@ static inline int init_new_context(struct task_struct *tsk, > return 0; > } > > +DECLARE_STATIC_KEY_FALSE(use_asid_allocator); > + > #include > > #endif /* _ASM_RISCV_MMU_CONTEXT_H */ > diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c > index 68aa312fc352..45c1b04b105d 100644 > --- a/arch/riscv/mm/context.c > +++ b/arch/riscv/mm/context.c > @@ -18,7 +18,7 @@ > > #ifdef CONFIG_MMU > > -static DEFINE_STATIC_KEY_FALSE(use_asid_allocator); > +DEFINE_STATIC_KEY_FALSE(use_asid_allocator); > > static unsigned long asid_bits; > static unsigned long num_asids; > diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c > index 720b443c4528..d8afbb1269d5 100644 > --- a/arch/riscv/mm/tlbflush.c > +++ b/arch/riscv/mm/tlbflush.c > @@ -4,6 +4,33 @@ > #include > #include > #include > +#include > + > +static inline void local_flush_tlb_all_asid(unsigned long asid) > +{ > + __asm__ __volatile__ ("sfence.vma x0, %0" > + : > + : "r" (asid) > + : "memory"); > +} > + > +static inline void local_flush_tlb_page_asid(unsigned long addr, > + unsigned long asid) > +{ > + __asm__ __volatile__ ("sfence.vma %0, %1" > + : > + : "r" (addr), "r" (asid) > + : "memory"); > +} > + > +static inline void local_flush_tlb_range_asid(unsigned long start, > + unsigned long size, unsigned long asid) > +{ > + unsigned long addr, end = ALIGN(start + size, PAGE_SIZE); > + > + for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) > + local_flush_tlb_page_asid(addr, asid); > +} > > void flush_tlb_all(void) > { > @@ -12,28 +39,43 @@ void flush_tlb_all(void) > > /* > * This function must not be called with cmask being null. > - * Kernel may panic if cmask is NULL. > */ > -static void __sbi_tlb_flush_range(struct cpumask *cmask, unsigned long start, > +static void __sbi_tlb_flush_range(struct mm_struct *mm, unsigned long start, > unsigned long size) > { > + struct cpumask *cmask = mm_cpumask(mm); > struct cpumask hmask; > unsigned int cpuid; > + bool broadcast; > > if (cpumask_empty(cmask)) > return; > > cpuid = get_cpu(); > + /* check if the tlbflush needs to be sent to other CPUs */ > + broadcast = cpumask_any_but(cmask, cpuid) < nr_cpu_ids; > + if (static_branch_unlikely(&use_asid_allocator)) { > + unsigned long asid = atomic_long_read(&mm->context.id); > > - if (cpumask_any_but(cmask, cpuid) >= nr_cpu_ids) { > - /* local cpu is the only cpu present in cpumask */ > - if (size <= PAGE_SIZE) > + if (broadcast) { > + riscv_cpuid_to_hartid_mask(cmask, &hmask); > + sbi_remote_sfence_vma_asid(cpumask_bits(&hmask), > + start, size, asid); > + } else if (size != -1) { > + local_flush_tlb_range_asid(start, size, asid); > + } else { > + local_flush_tlb_all_asid(asid); > + } > + } else { > + if (broadcast) { > + riscv_cpuid_to_hartid_mask(cmask, &hmask); > + sbi_remote_sfence_vma(cpumask_bits(&hmask), > + start, size); > + } else if (size <= PAGE_SIZE) { > local_flush_tlb_page(start); > - else > + } else { > local_flush_tlb_all(); > - } else { > - riscv_cpuid_to_hartid_mask(cmask, &hmask); > - sbi_remote_sfence_vma(cpumask_bits(&hmask), start, size); > + } > } > > put_cpu(); > @@ -41,16 +83,16 @@ static void __sbi_tlb_flush_range(struct cpumask *cmask, unsigned long start, > > void flush_tlb_mm(struct mm_struct *mm) > { > - __sbi_tlb_flush_range(mm_cpumask(mm), 0, -1); > + __sbi_tlb_flush_range(mm, 0, -1); > } > > void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr) > { > - __sbi_tlb_flush_range(mm_cpumask(vma->vm_mm), addr, PAGE_SIZE); > + __sbi_tlb_flush_range(vma->vm_mm, addr, PAGE_SIZE); > } > > void flush_tlb_range(struct vm_area_struct *vma, unsigned long start, > unsigned long end) > { > - __sbi_tlb_flush_range(mm_cpumask(vma->vm_mm), start, end - start); > + __sbi_tlb_flush_range(vma->vm_mm, start, end - start); > } -- Best Regards Guo Ren ML: https://lore.kernel.org/linux-csky/