From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 01F0B98642E for ; Mon, 31 Oct 2022 19:33:17 +0000 (UTC) Date: Mon, 31 Oct 2022 15:33:05 -0400 From: "Michael S. Tsirkin" Message-ID: <20221031153240-mutt-send-email-mst@kernel.org> References: <20221007165643.3920613-1-usama.arif@bytedance.com> <20221007165643.3920613-4-usama.arif@bytedance.com> <20221031114132-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: Subject: Re: [virtio-dev] Re: [PATCH v3 3/4] content: Introduce driver/device auxiliary notifications for MMIO Content-Type: text/plain; charset=us-ascii Content-Disposition: inline To: Stefan Hajnoczi Cc: Usama Arif , virtio-dev@lists.oasis-open.org, ndragazis@arrikto.com, fam.zheng@bytedance.com, liangma@liangbit.com List-ID: On Mon, Oct 31, 2022 at 01:24:30PM -0400, Stefan Hajnoczi wrote: > On Mon, Oct 31, 2022 at 11:45:55AM -0400, Michael S. Tsirkin wrote: > > On Thu, Oct 27, 2022 at 05:27:28PM -0400, Stefan Hajnoczi wrote: > > > On Fri, Oct 07, 2022 at 05:56:42PM +0100, Usama Arif wrote: > > > > This includes the additions to the corresponding device and driver > > > > conformances. > > > > > > > > Signed-off-by: Usama Arif > > > > Signed-off-by: Stefan Hajnoczi > > > > > > You can keep this. One thought: > > > > > > I realized that virtio-mmio support won't be very useful until > > > virtio-mmio gets MSI-X support because drivers currently cannot > > > differentiate between device auxiliary notifications. > > > > > > Stefan > > > > > > The big issue with MSI is it actually needs a ton of registers > > for interrupt rebalancing, masking etc and they need to be fast. > > Maybe a status bit like pci has makes sense here. > > This patch does add an ISR bit: > > diff --git a/content.tex b/content.tex > index 33362b7..8968fcd 100644 > --- a/content.tex > +++ b/content.tex > @@ -2049,6 +2049,8 @@ \subsection{MMIO Device Register Layout}\label{sec:Virtio Transport Options / Vi > in at least one of the active virtual queues. > \item [Configuration Change Notification] - bit 1 - the interrupt was > asserted because the configuration of the device has changed. > + \item [Device-specific Driver Auxiliary Notification] - bit 2 - the interrupt was > + asserted because a device-specific event occurred to notify the driver. > > The problem is that the driver doesn't know which device-specific event > occurred, so the mechanism is less useful than the MSI-X approach where > the driver knows exactly which (of potentially many) device-specific > events occurred. > > Stefan Right I figured that out after sending this. So it's limited to one event type. --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org