From patchwork Mon Jan 4 19:58:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexandre Ghiti X-Patchwork-Id: 356525 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 D9C2BC433E0 for ; Mon, 4 Jan 2021 20:09:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A412321BE5 for ; Mon, 4 Jan 2021 20:09:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727913AbhADUJE (ORCPT ); Mon, 4 Jan 2021 15:09:04 -0500 Received: from relay2-d.mail.gandi.net ([217.70.183.194]:53675 "EHLO relay2-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726492AbhADUJE (ORCPT ); Mon, 4 Jan 2021 15:09:04 -0500 X-Originating-IP: 90.112.190.212 Received: from debian.home (lfbn-gre-1-231-212.w90-112.abo.wanadoo.fr [90.112.190.212]) (Authenticated sender: alex@ghiti.fr) by relay2-d.mail.gandi.net (Postfix) with ESMTPSA id 4135E40007; Mon, 4 Jan 2021 20:08:20 +0000 (UTC) From: Alexandre Ghiti To: Paul Walmsley , Palmer Dabbelt , Zong Li , Anup Patel , Christoph Hellwig , Ard Biesheuvel , Arnd Bergmann , linux-efi@vger.kernel.org, linux-arch@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Alexandre Ghiti Subject: [RFC PATCH 09/12] riscv: Allow user to downgrade to sv39 when hw supports sv48 Date: Mon, 4 Jan 2021 14:58:37 -0500 Message-Id: <20210104195840.1593-10-alex@ghiti.fr> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210104195840.1593-1-alex@ghiti.fr> References: <20210104195840.1593-1-alex@ghiti.fr> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org This is made possible by using the mmu-type property of the cpu node of the device tree. By default, the kernel will boot with 4-level page table if the hw supports it but it can be interesting for the user to select 3-level page table as it is less memory consuming and faster since it requires less memory accesses in case of a TLB miss. Signed-off-by: Alexandre Ghiti Reviewed-by: Anup Patel --- arch/riscv/mm/init.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index cb23a30d9af3..f9a99cb1870b 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -550,10 +550,32 @@ void disable_pgtable_l4(void) * then read SATP to see if the configuration was taken into account * meaning sv48 is supported. */ -asmlinkage __init void set_satp_mode(uintptr_t load_pa) +asmlinkage __init void set_satp_mode(uintptr_t load_pa, uintptr_t dtb_pa) { u64 identity_satp, hw_satp; + int cpus_node; + /* 1/ Check if the user asked for sv39 explicitly in the device tree */ + cpus_node = fdt_path_offset((void *)dtb_pa, "/cpus"); + if (cpus_node >= 0) { + int node; + + fdt_for_each_subnode(node, (void *)dtb_pa, cpus_node) { + const char *mmu_type = fdt_getprop((void *)dtb_pa, node, + "mmu-type", NULL); + if (!mmu_type) + continue; + + if (!strcmp(mmu_type, "riscv,sv39")) { + disable_pgtable_l4(); + return; + } + + break; + } + } + + /* 2/ Determine if the HW supports sv48: if not, fallback to sv39 */ create_pgd_mapping(early_pg_dir, load_pa, (uintptr_t)early_pud, PGDIR_SIZE, PAGE_TABLE); create_pud_mapping(early_pud, load_pa, (uintptr_t)early_pmd, @@ -611,7 +633,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) #endif #if defined(CONFIG_64BIT) && !defined(CONFIG_MAXPHYSMEM_2GB) - set_satp_mode(load_pa); + set_satp_mode(load_pa, dtb_pa); #endif kernel_virt_addr = KERNEL_VIRT_ADDR;