From patchwork Wed Apr 9 00:08:30 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Kisel X-Patchwork-Id: 879286 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0D1851C32; Wed, 9 Apr 2025 00:08:44 +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=1744157326; cv=none; b=upVM4jy8GBeQxOwxQTwH6Bv8WTDbFUJR9D6uXj+UGRYCciUF4UjjZ4OcFV16lJiCs6+CdqSk/Y2DngKwPbA9jJDxyCvWTvUt5lgmNVGcSZcG9pt/ekWvg962CD7IPcZu62AE5dRd7xUeNW0gs45NeEpXyBDl9kq9KKPXCSGirk4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744157326; c=relaxed/simple; bh=FeY7FUjVyZnX86xAQafH+ENKHx7xrhl+RJwwvbDtetA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GQhozN1r3+7IGYG+gc9vDSwvbEhLDCAz2LPEDOL7xp3RBc7Yo/GyQJnX2NbXf1rC2gaxeECMyINQhPsAw9zpdkyTq4QX7MlWZkpMLk+p3tqofe3hfVbpizHec0Q29MwKOtq8XWSvzVeUBulaMM/wP1Cx/GtXfcgCS7FzItB33oA= 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=fQm9USqT; 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="fQm9USqT" Received: from romank-3650.corp.microsoft.com (unknown [131.107.160.188]) by linux.microsoft.com (Postfix) with ESMTPSA id 278202113E98; Tue, 8 Apr 2025 17:08:38 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 278202113E98 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1744157318; bh=ASGce+NyaGbEoSjdawfaStxr+cxlfQcFzJFI1lv07Aw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fQm9USqTIK36LAB4mqAvsqseTTmnZCrw+zHCmm9m+yyGhhqzi6bXCY9O+iMchHVrc W/4PTasl5/WaavJ0SoPdl1fdv1jRtRpnQKf1WJexVHnoVXObTXQQ81K3Kvi5IlTmoC YH2yCK8gsKTJc/v1dacCQvG3lBGHWH/xZ2RaG9j0= From: Roman Kisel To: aleksander.lobakin@intel.com, andriy.shevchenko@linux.intel.com, arnd@arndb.de, bp@alien8.de, catalin.marinas@arm.com, corbet@lwn.net, dakr@kernel.org, dan.j.williams@intel.com, dave.hansen@linux.intel.com, decui@microsoft.com, gregkh@linuxfoundation.org, haiyangz@microsoft.com, hch@lst.de, hpa@zytor.com, James.Bottomley@HansenPartnership.com, Jonathan.Cameron@huawei.com, kys@microsoft.com, leon@kernel.org, lukas@wunner.de, luto@kernel.org, m.szyprowski@samsung.com, martin.petersen@oracle.com, mingo@redhat.com, peterz@infradead.org, quic_zijuhu@quicinc.com, robin.murphy@arm.com, tglx@linutronix.de, wei.liu@kernel.org, will@kernel.org, iommu@lists.linux.dev, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, x86@kernel.org Cc: apais@microsoft.com, benhill@microsoft.com, bperkins@microsoft.com, sunilmut@microsoft.com Subject: [PATCH hyperv-next 1/6] Documentation: hyperv: Confidential VMBus Date: Tue, 8 Apr 2025 17:08:30 -0700 Message-ID: <20250409000835.285105-2-romank@linux.microsoft.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250409000835.285105-1-romank@linux.microsoft.com> References: <20250409000835.285105-1-romank@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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..f600e3d09800 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 trsuted 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.