From patchwork Thu Mar 10 21:38:36 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Maciej S. Szmigiero" X-Patchwork-Id: 12776946 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E3AABC433F5 for ; Thu, 10 Mar 2022 21:39:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232848AbiCJVkN (ORCPT ); Thu, 10 Mar 2022 16:40:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55554 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237075AbiCJVkL (ORCPT ); Thu, 10 Mar 2022 16:40:11 -0500 Received: from vps-vb.mhejs.net (vps-vb.mhejs.net [37.28.154.113]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 29FFABECC3; Thu, 10 Mar 2022 13:39:07 -0800 (PST) Received: from MUA by vps-vb.mhejs.net with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1nSQUh-0006Ir-2l; Thu, 10 Mar 2022 22:38:47 +0100 From: "Maciej S. Szmigiero" To: Paolo Bonzini Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Tom Lendacky , Brijesh Singh , Jon Grimm , David Kaplan , Boris Ostrovsky , Liam Merwick , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 0/5] nSVM: L1 -> L2 event injection fixes and a self-test Date: Thu, 10 Mar 2022 22:38:36 +0100 Message-Id: X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: "Maciej S. Szmigiero" There are some issues with respect to nSVM L1 -> L2 event injection. First, the next_rip field of a VMCB is *not* an output-only field for a VMRUN. This field value (instead of the saved guest RIP) in used by the CPU for the return address pushed on stack when injecting a software interrupt or INT3 or INTO exception (this was confirmed by AMD). On a VMRUN that does event injection it has similar function as VMX's VM_ENTRY_INSTRUCTION_LEN field, although, in contrast to VMX, it holds an absolute RIP value, not a relative increment. However, KVM seems to treat this field as a unidirectional hint from the CPU to the hypervisor - there seems to be no specific effort to maintain this field consistency for such VMRUN. This is mostly visible with running a nested guest, with L1 trying to inject an event into its L2. In this case, we need to make sure the next_rip field gets synced from vmcb12 to vmcb02. Another issue is that pending L1 -> L2 events are forgotten if there is an intervening L0 VMEXIT during their delivery. We need to make sure they are remembered (including their desired next_rip field value) until they are either re-injected into L2 successfully or returned back to L1 in the EXITINTINFO field upon a nested VMEXIT. A new KVM self-test that checks for the nSVM issues described above is included in this patch series. These issues are SVM-specific - all the use cases described above already work correctly with VMX. This patch set was tested with both Linux and Windows nested guests. KVM: nSVM: Sync next_rip field from vmcb12 to vmcb02 KVM: SVM: Downgrade BUG_ON() to WARN_ON() in svm_inject_irq() KVM: nSVM: Don't forget about L1-injected events KVM: nSVM: Restore next_rip when doing L1 -> L2 event re-injection KVM: selftests: nSVM: Add svm_nested_soft_inject_test arch/x86/kvm/svm/nested.c | 69 +++++++- arch/x86/kvm/svm/svm.c | 60 ++++++- arch/x86/kvm/svm/svm.h | 48 ++++++ tools/testing/selftests/kvm/.gitignore | 1 + tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/include/x86_64/svm_util.h | 2 + .../kvm/x86_64/svm_nested_soft_inject_test.c | 147 ++++++++++++++++++ 7 files changed, 324 insertions(+), 4 deletions(-) create mode 100644 tools/testing/selftests/kvm/x86_64/svm_nested_soft_inject_test.c