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[83.42.66.234]) by smtp.gmail.com with ESMTPSA id h2sm8046103wme.45.2020.11.18.22.09.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Nov 2020 22:09:16 -0800 (PST) Subject: Re: [RFC PATCH 0/5] ARM: reduce the memory consumed when mapping UEFI flash images To: Markus Armbruster , David Edmondson References: <20201116104216.439650-1-david.edmondson@oracle.com> <3da830b6-8200-6df9-9ba3-1f51bf887c4e@redhat.com> <87a6vhxvit.fsf@dusky.pond.sub.org> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: Date: Thu, 19 Nov 2020 07:09:14 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <87a6vhxvit.fsf@dusky.pond.sub.org> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/19 01:09:21 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] 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, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action 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: Kevin Wolf , Peter Maydell , qemu-block@nongnu.org, "Michael S. Tsirkin" , Xu Yandong , qemu-devel@nongnu.org, Max Reitz , Shannon Zhao , Zheng Xiang , qemu-arm@nongnu.org, =?UTF-8?B?aGFpYmluemhhbmco5byg5rW35paMKQ==?= , Igor Mammedov , John Snow Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 11/16/20 2:48 PM, Markus Armbruster wrote: > Philippe Mathieu-Daudé writes: > >> Hi David, >> >> On 11/16/20 11:42 AM, David Edmondson wrote: >>> Currently ARM UEFI images are typically built as 2MB/768kB flash >>> images for code and variables respectively. These images are both then >>> padded out to 64MB before being loaded by QEMU. >>> >>> Because the images are 64MB each, QEMU allocates 128MB of memory to >>> read them, and then proceeds to read all 128MB from disk (dirtying the >>> memory). Of this 128MB less than 3MB is useful - the rest is zero >>> padding. >> >> 2 years ago I commented the same problem, and suggested to access the >> underlying storage by "block", as this is a "block storage". >> >> Back then the response was "do not try to fix something that works". >> This is why we choose the big hammer "do not accept image size not >> matching device size" way. >> >> While your series seems to help, it only postpone the same >> implementation problem. If what you want is use the least memory >> required, I still believe accessing the device by block is the >> best approach. > > "Do not try to fix something that works" is hard to disagree with. > However, at least some users seem to disagree with "this works". Enough > to overcome the resistance to change? Yeah, at least 3 big users so far: - Huawei https://www.mail-archive.com/qemu-devel@nongnu.org/msg607292.html - Tencent https://www.mail-archive.com/qemu-devel@nongnu.org/msg742066.html - Oracle (this series). Then Huawei tried the MicroVM approach: https://www.mail-archive.com/qemu-devel@nongnu.org/msg680103.html I simply wanted to save David time by remembering this other approach, since Peter already commented on David's one (see Huawei link). Regards, Phil.