From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f50.google.com (mail-wm1-f50.google.com [209.85.128.50]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4739112D20D for ; Wed, 25 Sep 2024 09:23:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.50 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727256222; cv=none; b=l1haRu1fdFg6mT+X5y5QdKORGsSYgSE0FXrPp1Z1T1x5yUQ3GvKBMtZr0w8C8EpHdli+QD8sX2apiq5XIrYYaLth2SVHeP2cg/R31q6sIpE132SQ/wxSbYriVNsATg+5ywXZvHpAw5vwwQLLqIqL4M1SP4iTCyocMoyKB5Zl72A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727256222; c=relaxed/simple; bh=CsHNgHDX5NSd5k6WebfGUFU35z5a3oFsvU7LyCdz15k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YbpIYYymSafqk08Ppo094O2FKlTPpj2CecpMooiEDzr5+RBckKLqFADgiDdiiwPI4U5pFvAxqlvcz1YfokFbwys+LZjmIzN3NV+tbQk8I53R/sWAaTjWZN3qvF+fyzxD5f5lK7Ks+/7nX84uSD3CfEOeQnq9fzQs+dWHc3XE7qU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org; spf=pass smtp.mailfrom=linaro.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b=EY4Tcl0E; arc=none smtp.client-ip=209.85.128.50 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linaro.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="EY4Tcl0E" Received: by mail-wm1-f50.google.com with SMTP id 5b1f17b1804b1-42cb1758e41so53135205e9.1 for ; Wed, 25 Sep 2024 02:23:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1727256218; x=1727861018; darn=vger.kernel.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=Erl2ISmU+k1lGSmb71kUBr7EKO9urA/bALpyymmkCKY=; b=EY4Tcl0E4q9fYrFUiO0XrAgtXK8dNs3SVxIz4qz8lgSGa2+NVp7Q09YWZqojK7ZVHy 1tZ9J3xJrC6GDOQqQ48Y5TkZZuDsAjrQML3j7NYnekDmG/Wq8ykgxmy8KFaLWLDBqjng nd8kn1kOLmK8BHCTuc0gzviAj8poCmUJm3m96IfpZFmry1Lny81c0cuTCtR+0uxf9Cg0 ANBsy3842Qq8hTaRZpNV0fpwUi2Opd0KrxcOXI+LRu+hl7maz084EMPBcH3Ao5bYSHtO 7o7Insqkwynv+n+6p/uWIUcHd4md5M7ZrsEQkGCzA/iU8BQi5+TBWISkEe+13Ii5UJEc Gk4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1727256218; x=1727861018; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Erl2ISmU+k1lGSmb71kUBr7EKO9urA/bALpyymmkCKY=; b=cnOrJpZB6i9mfM1TcS2Y/rtDJJdOeYu9kgNdcNaPcTM0KpMDNA6CBJ2Km6UZPdzvkq jZ0wvgVrdCs1nS3wgwNIHzZQ8aZoGj8VCNUMt22sCxRPyVsRwPtrJyVJr0Wwe9jZkd4i CX34vJJEv6KAS2Sn25gJXP1cISC5SVbmROOwtrSJxNY0IAO6dN3JVhIwHsQsRagoKDG2 /ylwFCm9oGTIiwDsu8zytsXWNEBO0AXx+cD2Q7tdBdhjVFlIwfrr5clkBYaqRC3hyQxD xKVzZY/UK0Key1rwmmO/NxkWShB/m285MUhD+BZ9QQ+VM5/W6+jA9deB663vMMr5z6AV R+zQ== X-Forwarded-Encrypted: i=1; AJvYcCU3rnazMuKBvSw61qOiKftk4uGlrDgc8n2LzQ45171tZhT7Xj3r11nSdA5d2BmKEQ36Wj+Jw4upZTi72A==@vger.kernel.org X-Gm-Message-State: AOJu0Yz7MQIBONVui0Wyjxq1653kvD62Us9Bu4Iplx02ITiNC3jm9od6 5a8bSPWCE4ab97QMGQH/F54y1OryAYe7lOA1EaMo3zyihmPxiRvu7sCy3wEJVA== X-Google-Smtp-Source: AGHT+IHRfauL5Udmy6C13QIxy5atPl9zt31xORaSC3ESwbQ7cvwTL7aLRZCIbVJrka2xQA7ywfRrPQ== X-Received: by 2002:a05:600c:4755:b0:428:10ec:e5ca with SMTP id 5b1f17b1804b1-42e9610ac97mr13190325e9.14.1727256218476; Wed, 25 Sep 2024 02:23:38 -0700 (PDT) Received: from thinkpad ([80.66.138.17]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42e96a168bdsm12264245e9.37.2024.09.25.02.23.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Sep 2024 02:23:37 -0700 (PDT) Date: Wed, 25 Sep 2024 11:23:36 +0200 From: Manivannan Sadhasivam To: Wadim Mueller Cc: Bjorn Helgaas , Jonathan Corbet , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Kishon Vijay Abraham I , Jens Axboe , Lorenzo Pieralisi , Damien Le Moal , Shunsuke Mie , linux-pci@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: [PATCH 0/3] Add support for Block Passthrough Endpoint function driver Message-ID: <20240925092336.mf6plixpqe7fcsoa@thinkpad> References: <20240224210409.112333-1-wafgo01@gmail.com> <20240225160926.GA58532@thinkpad> <20240225203917.GA4678@bhlegrsu.conti.de> <20240226094530.GA2778@thinkpad> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Feb 26, 2024 at 07:47:30PM +0100, Wadim Mueller wrote: [...] > Okay, I understand this. The hypervisor was more of an example. I will > try to explain. > > I am currently reading through the virtio spec [1]. > In chapter 4.1.4.5.1 there is the following statement: > > "The device MUST reset ISR status to 0 on driver read." > > So I was wondering, how we, as an PCI EP Device, supposed to clear a > register when the driver reads the same register? I mean how do we detect a > register read? > If you are a hypervisor its easy to do so, because you can intercept > every memory access made my the guest (the same applies if you build > custom HW for this purpose). But for us as an EP device its > difficult to detect this, even with MSIs and Doorbell Registers in > place. > Sorry for not responding earlier. Conversation got lost. Yes, I do agree that some of the expecatations of the current Virtio spec cannot be satisfied by the physical endpoint device. So I presented some of these problems at this year plumbers and the Virtio maintainer in the room agreed to have changes in the spec to fix these issues. But it is not clear atm on whether we should introduce the changes in the virtio-pci transport or introduce a new transport altogether. I can include you in the discussions if you are still interested. - Mani -- மணிவண்ணன் சதாசிவம்