From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 153603D4131; Wed, 8 Apr 2026 16:55:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775667303; cv=none; b=tWZTxt1MEoX2oiT/SxDt/Ls5uRiv7EMOBC51YRPyq2GFW2yx0DbjeqmlcPUp8CJkCx4brWuBrvxEZb9jLVbywBgtYdvrdsJgSZl2HH2sugON0BIWjO4c9PwthK5E4Gie5GkDGWn/mngbsFaNPKBJQTGMxoZMBbRZJvDF7Og3LQ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775667303; c=relaxed/simple; bh=l9DP0GH9MCurTbEQAjdMKc4uZTFoMdfijB0YEpGLnNY=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=qbgfCl769l3lP3lkS9nPh/oPud23HDdAQ4miU4ohrR72KRbSXMEN3lGGiM/rxPHVVwFaZV8GqIxuRAsPjpbZ3nA/hvBmt5CgEKFLL9QYURFCJO2n3W1E4Dcq1Wbfz3/qAKK69XPN4RFNtFgQwSjiu5E+OoSRG7GgUyexH0M7ujg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=Pb3rU9Qw; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="Pb3rU9Qw" Received: from [10.17.145.186] (unknown [4.194.122.170]) by linux.microsoft.com (Postfix) with ESMTPSA id 234D120B710C; Wed, 8 Apr 2026 09:54:54 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 234D120B710C DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1775667301; bh=mD29zgGmHKg3hWcuJVIIaqH6LjpveyUTNfBgAyLvtHE=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=Pb3rU9QwvNHEwiYOVAh5gJPGtC33xq6v0fUTu3ZF84PMTL+oHXI7Di3V/rI70cZeq 499g33dTbLEdxy70aRYL2GJXyBJoYlmRt98XSg0m4WEFQqsV+M2LtoXhfuRDeGIdM3 MWqOTmVnp3BJ+DIZvXdkDj6A1P+jeFWoW/QYkHj8= Message-ID: <2a80b7a6-2cfe-4bd0-a799-ff855df7bd41@linux.microsoft.com> Date: Wed, 8 Apr 2026 09:54:52 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, longli@microsoft.com, James.Bottomley@HansenPartnership.com, martin.petersen@oracle.com, apais@microsoft.com, easwar.hariharan@linux.microsoft.com, Tianyu Lan , linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, vdso@hexbites.dev, mhklinux@outlook.com Subject: Re: [PATCH] x86/VMBus: Confidential VMBus for dynamic DMA transfers To: Tianyu Lan References: <20260408073105.272255-1-tiala@microsoft.com> From: Easwar Hariharan Content-Language: en-US In-Reply-To: <20260408073105.272255-1-tiala@microsoft.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/8/2026 12:31 AM, Tianyu Lan wrote: > Hyper-V provides Confidential VMBus to communicate between > device model and device guest driver via encrypted/private > memory in Confidential VM. The device model is in OpenHCL > (https://openvmm.dev/guide/user_guide/openhcl.html) that > plays the paravisor role. > > For a VMBus device, there are two communication methods to > talk with Host/Hypervisor. 1) VMBUS Ring buffer 2) Dynamic > DMA transfer. > > The Confidential VMBus Ring buffer has been upstreamed by > Roman Kisel(commit 6802d8af47d1). > > The dynamic DMA transition of VMBus device normally goes > through DMA core and it uses SWIOTLB as bounce buffer in > a CoCo VM. > > The Confidential VMBus device can do DMA directly to > private/encrypted memory. Because the swiotlb is decrypted > memory, the DMA transfer must not be bounced through the > swiotlb, so as to preserve confidentiality. This is different > from the default for Linux CoCo VMs, so not use DMA(SWIOTLB) > API in VMBus driver when confidential dynamic DMA transfers > capability is present. > > Signed-off-by: Tianyu Lan > --- > drivers/scsi/storvsc_drv.c | 28 +++++++++++++++++++++------- > include/linux/hyperv.h | 1 + > 2 files changed, 22 insertions(+), 7 deletions(-) > Does netvsc not need this same sort of patch? Thanks, Easwar (he/him)