From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qv1-f45.google.com (mail-qv1-f45.google.com [209.85.219.45]) (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 8EBDA41A50B for ; Mon, 17 Aug 2026 17:35:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.45 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786988157; cv=none; b=qr+dqr/Pkt/6aAz2MqH9ODxRNv/3HqZyWxUlp8Ch4iD/f21y5wOnnwejp4l/Mb2dsNbR/0wxNeEmlNi5r7BDQa2Gz8QydcW/cIDJhK/jTck8x0IybOleMcM9v65OjEzOrYTDxjzF5nTXps0+nqQ80y/HnG4g3JsUYgmjrRU7Zmk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786988157; c=relaxed/simple; bh=+e98k4168mAh10/uMiEYObv7JgiKCyhKONJNJqBtoX0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OsHJ5IIdDwfrXL4w7hCSl71yDG0v4XfG5hPbOIlbM8vwccyLwGbXrn2xIuji+CMKmQi4FBeU2AIxJ18/l6uBODC/CmlcZ/gw8XHhHWCRwUI+DfQoS5K4fmt3Od4BnebzfAfFMSyegZXjvB02lyf5LrnnpSKKRpuXPKZ6Mgp85qQ= 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=gw7r+pwV; arc=none smtp.client-ip=209.85.219.45 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="gw7r+pwV" Received: by mail-qv1-f45.google.com with SMTP id 6a1803df08f44-8f186025973so34250206d6.0 for ; Mon, 17 Aug 2026 10:35:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; t=1786988154; x=1787592954; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=7xTL49KfLwAq5Qv044eqsaTTNVVybZ9ovZEhY6mKMv0=; b=gw7r+pwV6rzaKBcmZKbwEorQMsOdlVWe4SFpxiD/v+PRtMIy4J6HyT5Oi7RHiQrWWs S7sgNNTz0bKsFxxJi4ZjqFSvTstHa3USTWT2Eipq3w3i5siHj0sMdeJ9G9HfzAN9AFGw AS/9rqZoB4O5CVatSRFs+PHzWOL8pLryM/kM8YG5pChw0pWNRZTJ/m0Bvs3BjAwXOAOY SlFoeDIVLBpfLDfq6xuZMB+RAtAaXbsiayBy7+lC48SmZo3iRK62RcUwpJOrqErVGTVF VDrG6vkwao1Nu9bVUxqDAOulVQVW88mTNz2SToj8FaeXahz2c02MFx4esKc7GrCtQmo1 4yPQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786988154; x=1787592954; h=in-reply-to:content-disposition:content-type: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 :content-type; bh=7xTL49KfLwAq5Qv044eqsaTTNVVybZ9ovZEhY6mKMv0=; b=RQdMUTxdMFXGVcxjnsBHDSu4rdgxdguj1+cy5fRIiLiIUjbxRCHPxdZFhh18/OWKOq ZCTk5QAAUG4ALxOxoWvuoMBpDMcXyAGjFpMFuYmZXnToWSYzO5QpXmtMtfCd51YIBeMh 5ljwb9qpH/DjlrWTtVj8Dr6TbAH4Gg9DQ0KMuyw1FS1XEOr6GpmAsKNHhVSgcL/DRowJ vsmf33iUd1yeqmrQJsFjFECQoVyTLyZwF6+5RYaJn66uN5dxwToGk7ZSptZ6WKitkulX Pr+VUJExMkovVLVCRSDwlvHsp6Sb2ysWqz7zD1Q5/65ewnSHzFcuoBnbRhbIgxIPB5Jl 9Dcg== X-Forwarded-Encrypted: i=1; AHgh+RqppiO0A3vO0bl5zJf8unOcqAT67hv5aZobD3ovDTYOPLRIQsVazFu8nDPC8M7nGG8bicPhBTwLM2qs8Jc=@vger.kernel.org X-Gm-Message-State: AOJu0YyVBkds3QM6A8HxaWn21SvITAQTvhow5aw5t3jZ/TC2wIdnM4c/ UrYVwybH9QhfNPWrxssQGy6y667i3fgZDdySvDAZYj3Hzj+H8f07u8SdII4gqvquIJ0= X-Gm-Gg: AR+sD11BIYJb0OuoQntadO+0Rqvi4w5WBJ1riAim9s0AVk46He47gqvbv9dEuH5BJhs zcQKDnCwXT5AZBlgfK/Han9a/qZy3/2ZWQ5EhEBLerUCQa4AchJSesrHxyCh3LdhgI8M5LgGzBw tBWQtcwaplSaQz0cfy2UMW5sq//avo/cLTtbC56R+CwjhaLy2iqNmzRzOBDFyF79llZCs85t6UP tMR6Qj902ynhWuUZNUHdluiRBt0KPwo87BtbPXFDaIweD99eDwj/bdkFHHm4dUkZGdQVrX4WrJ7 hDefZlUMwIth7DJUfq9Z8tWA43NRGWflW6hOpDixTlxsC+npNFbUEzyRK/oNG83al0/t1NRFap2 42tIRWntsjL7zbfAePbOCNiKhAhC8p2ABe+1yWAf09xSamKdRysPOmZcd3XWAv2eFUm03j9Wzt9 Qeh7KtfoHO4Zmqo2vDEKVayIy2btghcFT17GNDXA== X-Received: by 2002:a05:6214:e6e:b0:907:bf7a:9771 with SMTP id 6a1803df08f44-90a91def3cdmr277120766d6.21.1786988154391; Mon, 17 Aug 2026 10:35:54 -0700 (PDT) Received: from ziepe.ca ([142.166.156.215]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-90c4580f90csm13765356d6.9.2026.08.17.10.35.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Aug 2026 10:35:53 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1ww1FY-00000006A9C-3bVH; Mon, 17 Aug 2026 14:35:52 -0300 Date: Mon, 17 Aug 2026 14:35:52 -0300 From: Jason Gunthorpe To: Yu Zhang Cc: Jacob Pan , linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, iommu@lists.linux.dev, linux-pci@vger.kernel.org, linux-arch@vger.kernel.org, x86@kernel.org, wei.liu@kernel.org, kys@microsoft.com, haiyangz@microsoft.com, decui@microsoft.com, longli@microsoft.com, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, bhelgaas@google.com, kwilczynski@kernel.org, lpieralisi@kernel.org, mani@kernel.org, robh@kernel.org, arnd@arndb.de, mhklinux@outlook.com, tgopinath@linux.microsoft.com, easwar.hariharan@linux.microsoft.com, mrathor@linux.microsoft.com, baolu.lu@linux.intel.com, suravee.suthikulpanit@amd.com, vasant.hegde@amd.com Subject: Re: [PATCH v3 4/5] iommu/hyperv: Add para-virtualized IOMMU support for Hyper-V guest Message-ID: <20260817173552.GA1418894@ziepe.ca> References: <20260811155022.108148-1-zhangyu1@linux.microsoft.com> <20260811155022.108148-5-zhangyu1@linux.microsoft.com> <20260813152913.00003d8a@linux.microsoft.com> <20260813224627.GA933791@ziepe.ca> <20260817122216.GD933791@ziepe.ca> 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 Tue, Aug 18, 2026 at 01:22:03AM +0800, Yu Zhang wrote: > So we could > - either keep the duplicate check in hv_iommu_blocking_attach_dev(); > - or add code in our common helper, hv_iommu_attach_dev(), to treat > HV_STATUS_DEVICE_ALREADY_IN_DOMAIN also as successful explicitly. > > And since normal paging-domain attaches do not have this duplicate > case, I'd prefer the first choice, to keep current check in > hv_iommu_blocking_attach_dev(). I think everything can technically be re-attached and must not fail, you have to handle that possibility everywhere. So accepting that code as success seems like it might be needed anyhow? Jason