From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f170.google.com (mail-qk1-f170.google.com [209.85.222.170]) (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 A4CF626ED54 for ; Fri, 6 Feb 2026 14:30:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770388216; cv=none; b=nk7mYn0RlBFA1N1J8b6UH4wJQyvAXTxcw3C6TeA+Hs0/HnvwXJI5KGjaAJQGdEDCIhEDpv/0F56XBTndjNtAtxmJkU1QRSMR6SR2mUadvBivpk1anb34PAlt6AMCV0ELu+Qwb3MB0orhgShxhhg3HzR/az/xS26NuNmekzj9afU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770388216; c=relaxed/simple; bh=VJUJxiaiSyjn06mFjR9T+fjRixI6F335byZ5Sx4J6MA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=pW5qoPBjl99YMNQGQACdXa5MTd1SwVakAI25fWNX+B1DfSc1JaCoyDy6Cpx2hiEuusQ+PbqV36o7aiZeIDa2PHxR5Ueg4IJB+C3+1pgqs5f+S0uzWziLz+hz5glBIh3QYC5+8uaNorYWaKjr4WNwGh2Q/4nV3uB6hDsjcK2bCew= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ziepe.ca; spf=pass smtp.mailfrom=ziepe.ca; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b=MhRMdg6C; arc=none smtp.client-ip=209.85.222.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ziepe.ca Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ziepe.ca Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="MhRMdg6C" Received: by mail-qk1-f170.google.com with SMTP id af79cd13be357-8c5386f1c9fso103090885a.1 for ; Fri, 06 Feb 2026 06:30:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; t=1770388215; x=1770993015; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=THMhyPMr7sNTge9zhp9X3LUNdQ3UJ8Jh3cljXKT38Os=; b=MhRMdg6CtqlbF7iKKGKaGbhOxe1RV3MOMli+pKnDmCoLW/3bQkQp47HBogAV5D7wv6 0Dd9HrKr2h/dD53unnVrYBXOgqtU1LzggTT0bB0uNgru6HjjGKpkHHs2/ph2DLxC6ow8 BvLoU7ZfgyyXglMj9sLFegIz72JE3nc4uiEfaZ8RXYKskGvDiCStEVzdEt/dqFI1uJ/3 YPbCDAyhpNKSwna6wkV0BXGIA5Dp9INTXgG1K8W3Or7WD9Li5IY8EFDpmewKq1T6vo/x 2dgNLZhHQIbj0kUJxk8SoHfMSk+yukranDg8yjEwqv1t+XjW66u07c2vEC7/nOAeOmNf Yfww== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1770388215; x=1770993015; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=THMhyPMr7sNTge9zhp9X3LUNdQ3UJ8Jh3cljXKT38Os=; b=lObiF0pnzQZ8XlXSxSaunVvwyPpvGYxLr8ov4MYr13MPxAqo8oxzV3XV3rlGxyhfje 4cxe2Qz4EZDM8efWUVevIBg49j6ROQ0eO6iy8EV6bwYFKxnALLy4DAWuUOMdvVZOqO8M Z1qVfl7oOdSdKOizf8xG2fabw512i55GJED3/jQuhHEQgHyeI5yBqBwHovH4a/LUDjyG jtPQ8qaszBDp4K19t0E1rr4+vQu5iAiCtJpbuhOQhRL3y1qN4/WoixNjQYtbu/yRotA0 QNDA1okBwME2S3sH6a1uzhbwmSw9MiuXCzh5XDaF5ih2ZHGvxKBqraamI7c43cGF1Pbf VlNQ== X-Forwarded-Encrypted: i=1; AJvYcCWmg11r7+KBYjTTcIdpuunulMews3wXAlR3sK/AHrdq6XnmWGTAdNQ3kdJhKP6QawO9GZGF84uRWN/kvO8=@vger.kernel.org X-Gm-Message-State: AOJu0Yztfyvsd9TYZL5Vy3gjCEFrcJi3+NwVniJ+ksT9h+lTBRmBAvC8 Q5EnWONQwsSXgQD811jVyLibt4rS2G5T/fJHXB+XdVg/f3S/xCXT9M24JJi0oiOCyMk= X-Gm-Gg: AZuq6aKYYnHtuLPJ4xWVfgBtR5ZzoesgwujSWX+4E8ZA5O1ziqJHrSfb38f+BAQ5nBM VgdkWWCQGghNdOdA3OTMkZ4/CbnMgGpY5GfH/s1ldVBqMwS63jDfh3f42bHLbd+spNV5AZj+Yw1 2Y9Zh9ryob1rM6+jl0xLbY08Lm/No7+yG3MWs7pOIRxYfJuPM7l8tjnQnY6AecrPr2Z1sZRoFWf d4I+9Llkd4dDACtNCJKd2vlt1v5VYn6h3bEqKtX/84X38zIwsDg38NF4P8Nol79JhQQFUKTkxwr 8sqsE3e4HJM9/TcmTqRnVA0yYmUzHwvyGCw9dh4X4f4C8zu9WUAvYOYKgYg7V7Xsd+9pDXRldN8 40EQTyUGmM4869pp/khfxW/vDOLmjplXXnRw3UY8lpo/Gk3RBnEzlQZ5FKk/06PSsKiMe0B6ZBB EVfa+D1qsYErQTy9HSG3ZLGRufXfCW71Q605W7NuH8hJQvzIiSLnsTisqtSpnToqTz3XA= X-Received: by 2002:a05:620a:448c:b0:8c9:737e:3840 with SMTP id af79cd13be357-8caf130a55emr392847185a.67.1770388215425; Fri, 06 Feb 2026 06:30:15 -0800 (PST) Received: from ziepe.ca (hlfxns017vw-142-162-112-119.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.162.112.119]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8caf77f6badsm160617385a.11.2026.02.06.06.30.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Feb 2026 06:30:14 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1voMqc-00000008O8R-0VMF; Fri, 06 Feb 2026 10:30:14 -0400 Date: Fri, 6 Feb 2026 10:30:14 -0400 From: Jason Gunthorpe To: Manivannan Sadhasivam Cc: Bjorn Helgaas , Manivannan Sadhasivam , Bjorn Helgaas , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, Naresh Kamboju , Pavankumar Kondeti , Xingang Wang , Marek Szyprowski , Robin Murphy , Alex Williamson , James Puthukattukaran Subject: Re: [PATCH v3 3/4] PCI: Disable ACS SV capability for the broken IDT switches Message-ID: <20260206143014.GH943673@ziepe.ca> References: <20260102-pci_acs-v3-3-72280b94d288@oss.qualcomm.com> <20260205233920.GA17083@bhelgaas> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Feb 06, 2026 at 02:41:36PM +0530, Manivannan Sadhasivam wrote: > > It'd be worth expanding on this and what the effect of avoiding ACS SV > > is. Does this change which devices can be safely passed through to > > virtual guests? Does it give up isolation that users expect? > > > > IMO, ACS SV is somewhat broken on this switch. But we can still passthrough the > downstream devices to the guests. There won't be ACS SV apparently, but that's > what users will get with broken hw. I agree with this, the HW is very broken, let's have it at least work properly in Linux on bare metal out of the box. If someone really insists they need virtualization with narrow groups on this HW then they need to come with a more complete fix. Using VFIO is going to open up the reset flows that are problematic with the current solution, so it isn't like that is already working fully. Somehow I suspect nobody would use this switch for virtualization :) Jason