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[209.85.160.180]) by smtp.gmail.com with ESMTPSA id j22sm37991276qtp.0.2019.08.07.13.55.34 for (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Wed, 07 Aug 2019 13:55:35 -0700 (PDT) Received: by mail-qt1-f180.google.com with SMTP id k10so20705362qtq.1 for ; Wed, 07 Aug 2019 13:55:34 -0700 (PDT) X-Received: by 2002:ac8:23b3:: with SMTP id q48mr37884qtq.110.1565211334655; Wed, 07 Aug 2019 13:55:34 -0700 (PDT) MIME-Version: 1.0 References: <1564577101-29020-1-git-send-email-bmeng.cn@gmail.com> <581a0284-c658-265f-1b0f-6f4be5406cee@linaro.org> In-Reply-To: From: Palmer Dabbelt Date: Wed, 7 Aug 2019 13:55:23 -0700 X-Gmail-Original-Message-ID: Message-ID: To: Bin Meng X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::844 Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.23 Subject: Re: [Qemu-devel] [PATCH] riscv: rv32: Root page table address can be larger than 32-bit X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: QEMU riscv , Sagar Karandikar , Bastian Koppelmann , Palmer Dabbelt , Richard Henderson , QEMU devel , Alistair Francis Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Aug 1, 2019 at 7:58 AM Bin Meng wrote: > On Thu, Aug 1, 2019 at 10:16 PM Richard Henderson > wrote: > > > > On 7/31/19 6:53 PM, Bin Meng wrote: > > > I am not sure how (idx * ptesize) could overflow. It represents the > > > offset by a page table which is [0, 4096). > > > > You're right, I mis-read what was going on there. > > > > However, lower down, "target_ulong ppn" needs to be promoted to hwaddr, > so that > > > > ppn = pte >> PTE_PPN_SHIFT; > > ... > > base = ppn << PGSHIFT; > > > > does not overflow. (Which is the part of the page table walk that I > thought I > > had gleaned from the patch without actually reading the entire function.) > > Ah, yes. ppn should be promoted. Thanks for the review! > Did I miss a v2?