From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2B606C3ABCB for ; Sun, 11 May 2025 23:10:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=C6e1Sd2wwIBHFKi64bmr0cXUFCAbG2BTPif+GBdvk8k=; b=uFfoJ32q05Y2/LiJkkgEKuEs8Z t/tQjd7NxbznUKL2EFKVysak6xNIeNGX9jLeaHCMmaiQjHARwJPUIvwz/JX2YxEi7A6b8SGUBhpK5 l0Q6HRS0B+peEKuZ9JrgN2++oEqrIuyKQx7BQwdMSQsSg6dds+NPXk5wwnTuyjByQmfGXebYq2v+L 4blIfFVZMUQ/6wcC8ahInl9qJzXeBJxtqPfAye/ZK1rM+8MMdOQx5fAEYEgNtnpiI0auJN1Y2Gs8Z 2v4OJ3VCFIb7ccVq/rG7vPXE7wvxUkGdu9/uRe8rQP2YJ0rS/pZOXkf3O5aQpysLRanhRMRsWqCcC P/WfuNJA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uEFo9-000000080M6-3ROM; Sun, 11 May 2025 23:10:09 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uEFm6-00000007zkY-3ljW for linux-arm-kernel@lists.infradead.org; Sun, 11 May 2025 23:08:04 +0000 Received: from romank-3650.corp.microsoft.com (unknown [131.107.1.188]) by linux.microsoft.com (Postfix) with ESMTPSA id B2B49211D8B6; Sun, 11 May 2025 16:08:00 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com B2B49211D8B6 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1747004880; bh=C6e1Sd2wwIBHFKi64bmr0cXUFCAbG2BTPif+GBdvk8k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=i/uIweLM/AnCi7PqtxtdfyJTudA/+61xNiWRDAoghEYqfW7si/lWX7uVlaaVMDyX4 9jA91EjAJ3yihJuaC9vdYgkFDLfWxORvxvnRIEuSYhal1jDUg7Xu1XR3GOg9Em6cLH npeCsKoJGHstFIFm1zrocmvdPk38BL1CW+0I/kEY= From: Roman Kisel To: arnd@arndb.de, bp@alien8.de, catalin.marinas@arm.com, corbet@lwn.net, dave.hansen@linux.intel.com, decui@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com, kys@microsoft.com, mingo@redhat.com, tglx@linutronix.de, wei.liu@kernel.org, will@kernel.org, x86@kernel.org, linux-hyperv@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org Cc: apais@microsoft.com, benhill@microsoft.com, bperkins@microsoft.com, sunilmut@microsoft.com Subject: [PATCH hyperv-next v2 1/4] Documentation: hyperv: Confidential VMBus Date: Sun, 11 May 2025 16:07:55 -0700 Message-ID: <20250511230758.160674-2-romank@linux.microsoft.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250511230758.160674-1-romank@linux.microsoft.com> References: <20250511230758.160674-1-romank@linux.microsoft.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250511_160802_985209_C60A7FA2 X-CRM114-Status: GOOD ( 13.13 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Define what the confidential VMBus is and describe what advantages it offers on the capable hardware. Signed-off-by: Roman Kisel --- Documentation/virt/hyperv/vmbus.rst | 41 +++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/Documentation/virt/hyperv/vmbus.rst b/Documentation/virt/hyperv/vmbus.rst index 1dcef6a7fda3..ca2b948e5070 100644 --- a/Documentation/virt/hyperv/vmbus.rst +++ b/Documentation/virt/hyperv/vmbus.rst @@ -324,3 +324,44 @@ rescinded, neither Hyper-V nor Linux retains any state about its previous existence. Such a device might be re-added later, in which case it is treated as an entirely new device. See vmbus_onoffer_rescind(). + +Confidential VMBus +------------------ + +The confidential VMBus provides the control and data planes where +the guest doesn't talk to either the hypervisor or the host. Instead, +it relies on the trusted paravisor. The hardware (SNP or TDX) encrypts +the guest memory and the register state also measuring the paravisor +image via using the platform security processor to ensure trusted and +confidential computing. + +To support confidential communication with the paravisor, a VMBus client +will first attempt to use regular, non-isolated mechanisms for communication. +To do this, it must: + +* Configure the paravisor SIMP with an encrypted page. The paravisor SIMP is + configured by setting the relevant MSR directly, without using GHCB or tdcall. + +* Enable SINT 2 on both the paravisor and hypervisor, without setting the proxy + flag on the paravisor SINT. Enable interrupts on the paravisor SynIC. + +* Configure both the paravisor and hypervisor event flags page. + Both pages will need to be scanned when VMBus receives a channel interrupt. + +* Send messages to the paravisor by calling HvPostMessage directly, without using + GHCB or tdcall. + +* Set the EOM MSR directly in the paravisor, without using GHCB or tdcall. + +If sending the InitiateContact message using non-isolated HvPostMessage fails, +the client must fall back to using the hypervisor synic, by using the GHCB/tdcall +as appropriate. + +To fall back, the client will have to reconfigure the following: + +* Configure the hypervisor SIMP with a host-visible page. + Since the hypervisor SIMP is not used when in confidential mode, + this can be done up front, or only when needed, whichever makes sense for + the particular implementation. + +* Set the proxy flag on SINT 2 for the paravisor. -- 2.43.0