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Thu, 12 Aug 2021 23:38:11 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mEKGx-00BTsm-QD for linux-snps-arc@lists.infradead.org; Thu, 12 Aug 2021 23:38:08 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 204C86109F; Thu, 12 Aug 2021 23:38:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628811482; bh=Jvemhc6NK+B85RnvnFOWoDrTakqtEWuGs1UKrKyANmU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ido4Na3TV+bU6rUPv7EqSinKJX4s2BCubbt0YOja5AkqcyvCgaKyZxoURN5dq0sQ5 4Szcj2DRWNI4n+VdNRzdjf/WTcnDR/sFlcn/dlIW/PA8O+15aWQeQtM6stnG17wJ5S 7DWHwEvEA+0fc6t9KLaG0Ls1Y08rrvZ1893noPHT5P/3l4AAjFbK6Mgc22ZssdVyWJ hTjKUqHLsAI0vF2BTCX3MMBuQI6X115LHn7/k4ZAziRE0GqIk85CJemkNJNm/oI+EB gXMhsLQOWPjtNTsJBlJbExC7Om5SwEky8LySkkptpImSNm25rzCSGhHwKrsWvuYpas LfWF4py32WNEg== From: Vineet Gupta To: linux-snps-arc@lists.infradead.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Anshuman Khandual , Mike Rapoport , Vineet Gupta Subject: [PATCH v2 11/19] ARC: mm: move MMU specific bits out of ASID allocator Date: Thu, 12 Aug 2021 16:37:45 -0700 Message-Id: <20210812233753.104217-12-vgupta@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210812233753.104217-1-vgupta@kernel.org> References: <20210812233753.104217-1-vgupta@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210812_163803_940480_27D7CF35 X-CRM114-Status: GOOD ( 15.64 ) X-BeenThere: linux-snps-arc@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux on Synopsys ARC Processors List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+linux-snps-arc=archiver.kernel.org@lists.infradead.org And while at it, rewrite commentary on ASID allocator Signed-off-by: Vineet Gupta --- arch/arc/include/asm/mmu.h | 13 +++++++++++++ arch/arc/include/asm/mmu_context.h | 28 +++++++++++++--------------- arch/arc/mm/tlb.c | 11 ++++------- 3 files changed, 30 insertions(+), 22 deletions(-) diff --git a/arch/arc/include/asm/mmu.h b/arch/arc/include/asm/mmu.h index 762cfe66e16b..0b117ea07048 100644 --- a/arch/arc/include/asm/mmu.h +++ b/arch/arc/include/asm/mmu.h @@ -64,6 +64,19 @@ typedef struct { unsigned long asid[NR_CPUS]; /* 8 bit MMU PID + Generation cycle */ } mm_context_t; +static void inline mmu_setup_asid(struct mm_struct *mm, unsigned int asid) +{ + write_aux_reg(ARC_REG_PID, asid | MMU_ENABLE); +} + +static void inline mmu_setup_pgd(struct mm_struct *mm, void *pgd) +{ + /* PGD cached in MMU reg to avoid 3 mem lookups: task->mm->pgd */ +#ifdef CONFIG_ISA_ARCV2 + write_aux_reg(ARC_REG_SCRATCH_DATA0, (unsigned int)pgd); +#endif +} + static inline int is_pae40_enabled(void) { return IS_ENABLED(CONFIG_ARC_HAS_PAE40); diff --git a/arch/arc/include/asm/mmu_context.h b/arch/arc/include/asm/mmu_context.h index 49318a126879..dda471f5f05b 100644 --- a/arch/arc/include/asm/mmu_context.h +++ b/arch/arc/include/asm/mmu_context.h @@ -15,22 +15,23 @@ #ifndef _ASM_ARC_MMU_CONTEXT_H #define _ASM_ARC_MMU_CONTEXT_H -#include -#include #include +#include #include -/* ARC700 ASID Management +/* ARC ASID Management + * + * MMU tags TLBs with an 8-bit ASID, avoiding need to flush the TLB on + * context-switch. * - * ARC MMU provides 8-bit ASID (0..255) to TAG TLB entries, allowing entries - * with same vaddr (different tasks) to co-exit. This provides for - * "Fast Context Switch" i.e. no TLB flush on ctxt-switch + * ASID is managed per cpu, so task threads across CPUs can have different + * ASID. Global ASID management is needed if hardware supports TLB shootdown + * and/or shared TLB across cores, which ARC doesn't. * - * Linux assigns each task a unique ASID. A simple round-robin allocation - * of H/w ASID is done using software tracker @asid_cpu. - * When it reaches max 255, the allocation cycle starts afresh by flushing - * the entire TLB and wrapping ASID back to zero. + * Each task is assigned unique ASID, with a simple round-robin allocator + * tracked in @asid_cpu. When 8-bit value rolls over,a new cycle is started + * over from 0, and TLB is flushed * * A new allocation cycle, post rollover, could potentially reassign an ASID * to a different task. Thus the rule is to refresh the ASID in a new cycle. @@ -93,7 +94,7 @@ static inline void get_new_mmu_context(struct mm_struct *mm) asid_mm(mm, cpu) = asid_cpu(cpu); set_hw: - write_aux_reg(ARC_REG_PID, hw_pid(mm, cpu) | MMU_ENABLE); + mmu_setup_asid(mm, hw_pid(mm, cpu)); local_irq_restore(flags); } @@ -146,10 +147,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, */ cpumask_set_cpu(cpu, mm_cpumask(next)); -#ifdef CONFIG_ISA_ARCV2 - /* PGD cached in MMU reg to avoid 3 mem lookups: task->mm->pgd */ - write_aux_reg(ARC_REG_SCRATCH_DATA0, next->pgd); -#endif + mmu_setup_pgd(next, next->pgd); get_new_mmu_context(next); } diff --git a/arch/arc/mm/tlb.c b/arch/arc/mm/tlb.c index 15cbc285b0de..b68d5798327b 100644 --- a/arch/arc/mm/tlb.c +++ b/arch/arc/mm/tlb.c @@ -716,14 +716,11 @@ void arc_mmu_init(void) if (IS_ENABLED(CONFIG_ARC_HAS_PAE40) && !mmu->pae) panic("Hardware doesn't support PAE40\n"); - /* Enable the MMU */ - write_aux_reg(ARC_REG_PID, MMU_ENABLE); + /* Enable the MMU with ASID 0 */ + mmu_setup_asid(NULL, 0); - /* In arc700/smp needed for re-entrant interrupt handling */ -#ifdef CONFIG_ISA_ARCV2 - /* swapper_pg_dir is the pgd for the kernel, used by vmalloc */ - write_aux_reg(ARC_REG_SCRATCH_DATA0, swapper_pg_dir); -#endif + /* cache the pgd pointer in MMU SCRATCH reg (ARCv2 only) */ + mmu_setup_pgd(NULL, swapper_pg_dir); if (pae40_exist_but_not_enab()) write_aux_reg(ARC_REG_TLBPD1HI, 0); -- 2.25.1 _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc