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[88.187.86.199]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-477bf3b4c13sm182560995e9.13.2025.11.24.00.48.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Nov 2025 00:48:57 -0800 (PST) Message-ID: Date: Mon, 24 Nov 2025 09:48:56 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: 64mb limitation of qemu-system-sh4 board Content-Language: en-US To: John Paul Adrian Glaubitz , Rob Landley , Thorsten Glaser , Michael Tokarev , QEMU Developers Cc: Yoshinori Sato , Rich Felker , linux-sh@vger.kernel.org References: <6abe2750-5e2c-43a1-be57-1dc2ccabdd91@tls.msk.ru> <119d5858-52f4-ce1b-9ee7-9615ce2054b9@debian.org> <79f14fef-123f-4938-b069-10f07e7d0405@landley.net> <91b74af52f69c360a27269ab3145eeb377ef816a.camel@physik.fu-berlin.de> From: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= In-Reply-To: <91b74af52f69c360a27269ab3145eeb377ef816a.camel@physik.fu-berlin.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::32f; envelope-from=philmd@linaro.org; helo=mail-wm1-x32f.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 24/11/25 08:33, John Paul Adrian Glaubitz wrote: > Hi Philippe, > > On Mon, 2025-11-24 at 08:31 +0100, Philippe Mathieu-Daudé wrote: >> On 24/8/25 20:07, Rob Landley wrote: >>> On 8/23/25 09:19, Thorsten Glaser wrote: >>>>> There are no alternatives - qemu is unique in this regard.  And >>>>> it has never been designed for this usage.  What we had for 15+ >>>>> years, unnoticed, is like `chmod u+s /bin/sh`, which is never >>>>> supposed to be used like this. >>>> >>>> Perhaps, but there’s shades in between. >>> >>> I find qemu system emulation a LOT less problematic. >>> >>> For sh4 I boot qemu-system-sh4 and then use a network block device to >>> provide swap (so the 64mb limitation of the board isn't a limiting >>> factor). >> >> The R2D+ board uses a SH7751 SoC, which memory controller can access >> 7 external banks. This board has its boot flash on CS#0, a FPGA on CS#1, >> 64MB of SDRAM on CS#3, a SM501 display on CS#4 and some ISA bus on CS#5; >> leaving CS#2, and CS#6 available. CS#2 can have SDRAM, while CS#6 only >> SRAM (not really a difference in emulation). >> >> From QEMU side, we could fill these empty slots with 2*64MB of RAM, so >> the machine could use up to 192MB. But then it is up to the guest to >> use it. >> >> Looking at Linux i.e. it seems to hardcode the RAM base/size in >> arch/sh/include/asm/page.h, so we'd need changes there to use more >> memory, which seems unlikely to get for a such old board... > > I'm the upstream kernel maintainer for arch/sh and I would be happy to make > the necessary changes to get the Linux kernel support more than 64 MB in > QEMU. Great :) I should post something shortly so you can play with. Regards, Phil.