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[2.7.60.249]) by smtp.gmail.com with ESMTPSA id h18sm133008wrs.75.2021.09.29.08.01.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Sep 2021 08:01:47 -0700 (PDT) From: Alexandre Ghiti To: Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , Zong Li , Anup Patel , Atish Patra , Christoph Hellwig , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Ard Biesheuvel , Arnd Bergmann , Kees Cook , Guo Ren , Heinrich Schuchardt , Mayuresh Chitale , linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-efi@vger.kernel.org, linux-arch@vger.kernel.org Cc: Alexandre Ghiti Subject: [PATCH v2 10/10] riscv: Allow user to downgrade to sv39 when hw supports sv48 Date: Wed, 29 Sep 2021 16:51:13 +0200 Message-Id: <20210929145113.1935778-11-alexandre.ghiti@canonical.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210929145113.1935778-1-alexandre.ghiti@canonical.com> References: <20210929145113.1935778-1-alexandre.ghiti@canonical.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- arch/riscv/mm/init.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index a304f2b3c178..676635f5d98a 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -641,10 +641,31 @@ static void __init disable_pgtable_l4(void) * then read SATP to see if the configuration was taken into account * meaning sv48 is supported. */ -static __init void set_satp_mode(void) +static __init void set_satp_mode(uintptr_t dtb_pa) { u64 identity_satp, hw_satp; uintptr_t set_satp_mode_pmd; + int cpus_node; + + /* 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; + } + } set_satp_mode_pmd = ((unsigned long)set_satp_mode) & PMD_MASK; create_pgd_mapping(early_pg_dir, @@ -802,7 +823,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) #endif #if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL) - set_satp_mode(); + set_satp_mode(dtb_pa); #endif kernel_map.va_pa_offset = PAGE_OFFSET - kernel_map.phys_addr; -- 2.30.2