From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by 2002:a05:7022:120c:b0:76:3752:a982 with SMTP id ox12csp40942dlb; Tue, 27 Feb 2024 22:30:03 -0800 (PST) X-Forwarded-Encrypted: i=2; AJvYcCXen6NEltms98vfU9fK+L8m2PjPOzuk+YyKI4Ww901QQjtes5lv2zT6jeiI7OoKbm90x8ItCvf9JkYepJ6tF/vJjOKxW+w6 X-Google-Smtp-Source: AGHT+IGv3lxdGwUXF9m9bQ50CLrvnqGV1/PN1yXnUlgehcHSP/tQC0+bb6aPYn+femGVMtVouqW4 X-Received: by 2002:a05:620a:5e11:b0:787:bdc5:7cb0 with SMTP id xz17-20020a05620a5e1100b00787bdc57cb0mr4259480qkn.3.1709101803099; Tue, 27 Feb 2024 22:30:03 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1709101803; cv=none; d=google.com; s=arc-20160816; b=gv5ZPtNioH7hRo9/cYDurqg/+xEkxxh8lVjeM+kj54e34f5w5u03uo268IpB1Qf1Za tw0ACzWchq2t//nIMf53Y18RDPvYxhJXcBgoQA7Jtb4rGxa/6LoKKzo5H+S8DJx5SWY0 xCmFQ0k12Ude5JeCStIJ9oHCKJNQQS3P2f5fjY9QmXSBvSSsMXfU53Qbr7d/oXEF5ZJd 3B7e/BJUIYc+flTF0VmoblUaqwe2mMZoD8on+XfhgP9bCzVKkOpYXCSQAK7r0NcYcH2F M5RYNT68Xr5mamo6jrHbZRXf27bfhwHKGWFOSZopLtBz7Vwi6VFSeWuVt7UKycyaUwVH Ej8A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:message-id:date:references:in-reply-to :subject:cc:to:from:dkim-signature; bh=HtJcM8MeiQuDt8oTen0T+D/ITXNS5s2KD/Y3kyt7mo0=; fh=J2ghTm4PdECeW0dOE4goFbMA3ATHz+aLwgaexA57/d0=; b=T1wYxg/vHc9ygqnaSnFn549xerpXr6ujrbmz73AZC/qfUjKQSRVlAy8uCXg/eGI9BV XiKxyVXQm1af9195JmldRAgkoMTdOhxmY6YmRPF+IsugnFbh9pH2nBX791hS0UCwODJQ vEPhQZRt5TKcZGgvqLc+3h4qk5x9dfd7bqT6zyRGrfRndWXMD5trKw/KyTqaluYxgHop cYC6lYNCse1RP90UKLjGNOAmq7wIoCFUP+Px59sorPHkktKgWBZq0fG3UDZzgqTzWJQs 4XuPflIJimxMo9dnjeZ+IRPUeurrudxFfDdQRQrvR1lSxxZ8sGaEbo3yzXONhHmD3dEd um6A==; dara=google.com ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=LtVvPCKN; spf=pass (google.com: domain of armbru@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=armbru@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com. [170.10.129.124]) by mx.google.com with ESMTPS id f21-20020a05620a20d500b00787b7df206esi8794099qka.201.2024.02.27.22.30.02 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Feb 2024 22:30:03 -0800 (PST) Received-SPF: pass (google.com: domain of armbru@redhat.com designates 170.10.129.124 as permitted sender) client-ip=170.10.129.124; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=LtVvPCKN; spf=pass (google.com: domain of armbru@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=armbru@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709101802; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=HtJcM8MeiQuDt8oTen0T+D/ITXNS5s2KD/Y3kyt7mo0=; b=LtVvPCKNHfS9e7Ujul8qJRjIEVXdA/MOLEGJo5xloeQjIvzqsqgQWoIw1Ctt1I4rDI0ONj phoy3y40wxnlN7kIZ6l4c/ooJsSRCHHdSfFrfdh5zhwKKUpvSWsARWSvqspny/aPzZ2xi0 vEKcI5260qGiTI+yaUi4FMPpN/Pm96Q= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-557-dA63K2UUMD2ZLXRxMCZ57g-1; Wed, 28 Feb 2024 01:30:00 -0500 X-MC-Unique: dA63K2UUMD2ZLXRxMCZ57g-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7644785CE43; Wed, 28 Feb 2024 06:30:00 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.4]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5252DC185C3; Wed, 28 Feb 2024 06:30:00 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 257AC21E66F4; Wed, 28 Feb 2024 07:29:59 +0100 (CET) From: Markus Armbruster To: Gustavo Romero Cc: qemu-devel@nongnu.org, philmd@linaro.org, thuth@redhat.com, lvivier@redhat.com, qemu-arm@nongnu.org, alex.bennee@linaro.org, pbonzini@redhat.com, anton.kochkov@proton.me, richard.henderson@linaro.org, peter.maydell@linaro.org Subject: Re: [PATCH 0/6] Add ivshmem-flat device In-Reply-To: <20240222222218.2261956-1-gustavo.romero@linaro.org> (Gustavo Romero's message of "Thu, 22 Feb 2024 22:22:12 +0000") References: <20240222222218.2261956-1-gustavo.romero@linaro.org> Date: Wed, 28 Feb 2024 07:29:59 +0100 Message-ID: <87wmqp3xug.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 X-TUID: xMso3COBRt6r Gustavo Romero writes: [...] > This patchset introduces a new device, ivshmem-flat, which is similar to the > current ivshmem device but does not require a PCI bus. It implements the ivshmem > status and control registers as MMRs and the shared memory as a directly > accessible memory region in the VM memory layout. It's meant to be used on > machines like those with Cortex-M MCUs, which usually lack a PCI bus, e.g., > lm3s6965evb and mps2-an385. Additionally, it has the benefit of requiring a tiny > 'device driver,' which is helpful on some RTOSes, like Zephyr, that run on > memory-constrained resource targets. > > The patchset includes a QTest for the ivshmem-flat device, however, it's also > possible to experiment with it in two ways: > > (a) using two Cortex-M VMs running Zephyr; or > (b) using one aarch64 VM running Linux with the ivshmem PCI device and another > arm (Cortex-M) VM running Zephyr with the new ivshmem-flat device. > > Please note that for running the ivshmem-flat QTests the following patch, which > is not committed to the tree yet, must be applied: > > https://lists.nongnu.org/archive/html/qemu-devel/2023-11/msg03176.html What problem are you trying to solve with ivshmem? Shared memory is not a solution to any communication problem, it's merely a building block for building such solutions: you invariably have to layer some protocol on top. What do you intend to put on top of ivshmem? [...]