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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=8I8m7SSC/snr0cHsf2WBlkwE7bpgw/OQ5jKqCBoq9zo=; b=ZXVp86feEbRVxYoFJl0OVK5G/0fGpjjfHE/YY6eJqG05r7Ysvkc6byFxECzcE80+9T nCKc5kA0sjFDPydd7QCrUGqJyiiR0RyAgzC6uof4aOzqdbXAdTDNy/ZGiAecGk68fDb+ Wlzlr3KFdbFA4wQbBnj3nCbvbkAmvCLZjDzblLfk/YLgMtKFuuw5o3tpFSEInsHET9YC vNAZoanNmgaoNLuW/ywnlj5P1IFF6C6pqQRrCostCjDbjlgMEWTnv+aVly3tSu1EiNRB 8loVDvDUYUvW+hNRuLfzaUvF3ZjtQV7WrKQBhR7hTnfxsKJHe7Pp1eeuCSP4Jnr1wNfO wYmA== X-Gm-Message-State: APjAAAXSNglQYguv+6PrNhWB1mFEL9VCno+p5De5sso9rw0XW5z8maJZ Hpb0KdBGNh65pmO4AtaMuEdA0Kf+ttiSXBRCVBXJDA== X-Google-Smtp-Source: APXvYqwvVpi/LoncOYPYpBig+SQjHxP1DEaiXzYYe2cURFDrQOVHHYJ4xS0lDAEgDIJDOniOxhm435shCG4GgfH5Ksw= X-Received: by 2002:adf:f6c8:: with SMTP id y8mr6002760wrp.61.1554444081974; Thu, 04 Apr 2019 23:01:21 -0700 (PDT) MIME-Version: 1.0 References: <20190405054909.3238-1-anup.patel@wdc.com> <20190405055421.GA7087@infradead.org> In-Reply-To: <20190405055421.GA7087@infradead.org> From: Anup Patel Date: Fri, 5 Apr 2019 11:31:11 +0530 Message-ID: Subject: Re: [PATCH v3] RISC-V: Fix Maximum Physical Memory 2GiB option for 64bit systems To: Christoph Hellwig X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190404_230124_222544_067CF24E X-CRM114-Status: GOOD ( 12.73 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Palmer Dabbelt , Anup Patel , "linux-kernel@vger.kernel.org" , Mike Rapoport , Atish Patra , Albert Ou , Paul Walmsley , "linux-riscv@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org On Fri, Apr 5, 2019 at 11:24 AM Christoph Hellwig wrote: > > On Fri, Apr 05, 2019 at 05:49:34AM +0000, Anup Patel wrote: > > The Maximum Physical Memory 2GiB option for 64bit systems is currently > > broken because kernel hangs at boot-time when this option is enabled > > and the underlying system has more than 2GiB memory. > > > > This issue can be easily reproduced on SiFive Unleashed board where > > we have 8GiB of memory. > > > > This patch fixes above issue by removing unusable memory region in > > setup_bootmem(). > > > > Signed-off-by: Anup Patel > > Reviewed-by: Christoph Hellwig > > Btw, what is the rationale behind even offering the 2GiB option and > the medlow model on 64-bit? Do we reall have use cases where the > slightly more effient generated code matters so much to keep up > the support burden of this mostly unused and unusual configuration? Yes, if we want to use medlow with 64bit then max physical memory can be 2GiB. Otherwise, I don't any practical use of restricting max physical memory to 2GiB on 64bit systems. BTW, as-per latest revision of RISC-V priviledge spece the MMU SV32 mode will be able to access 34bit physical memory (i.e. 16GiB) so max physical memory 2GiB will also be required for 32bit system for medlow. Regards, Anup _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv