From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752456AbdJTCgR (ORCPT ); Thu, 19 Oct 2017 22:36:17 -0400 Received: from mail-bl2nam02on0071.outbound.protection.outlook.com ([104.47.38.71]:59884 "EHLO NAM02-BL2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752297AbdJTCgA (ORCPT ); Thu, 19 Oct 2017 22:36:00 -0400 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=brijesh.singh@amd.com; From: Brijesh Singh To: kvm@vger.kernel.org Cc: bp@alien8.de, Brijesh Singh , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Joerg Roedel , Borislav Petkov , Tom Lendacky , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [Part2 PATCH v6 38/38] KVM: X86: Restart the guest when insn_len is zero and SEV is enabled Date: Thu, 19 Oct 2017 21:34:13 -0500 Message-Id: <20171020023413.122280-39-brijesh.singh@amd.com> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20171020023413.122280-1-brijesh.singh@amd.com> References: <20171020023413.122280-1-brijesh.singh@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Originating-IP: [165.204.78.1] X-ClientProxiedBy: MWHPR1701CA0020.namprd17.prod.outlook.com (10.172.58.30) To SN1PR12MB0157.namprd12.prod.outlook.com (10.162.3.144) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 0178cb4a-fc3b-4c5a-f459-08d5176347d3 X-MS-Office365-Filtering-HT: Tenant X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(22001)(48565401081)(4534020)(4602075)(4627075)(201703031133081)(201702281549075)(2017052603199);SRVR:SN1PR12MB0157; 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This can happen if a guest gets a page-fault on data access but the HW table walker is not able to read the instruction page (e.g instruction page is not present in memory). Typically, when insn_len is zero, x86_emulate_instruction() walks the guest page table and fetches the instruction bytes from guest memory. When SEV is enabled, the guest memory is encrypted with guest-specific key hence hypervisor will not able to fetch the instruction bytes. In those cases we simply restart the guest. I have encountered this issue when running kernbench inside the guest. Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Joerg Roedel Cc: Borislav Petkov Cc: Tom Lendacky Cc: x86@kernel.org Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Brijesh Singh --- arch/x86/kvm/mmu.c | 10 ++++++++++ arch/x86/kvm/svm.c | 3 ++- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 7a69cf053711..0d4776b855bb 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -4954,6 +4954,16 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code, if (mmio_info_in_cache(vcpu, cr2, direct)) emulation_type = 0; emulate: + /* + * On AMD platforms, under certain conditions insn_len may be zero on #NPF. + * This can happen if a guest gets a page-fault on data access but the HW + * table walker is not able to read the instruction page (e.g instruction + * page is not present in memory). In those cases we simply restart the + * guest. + */ + if (unlikely(insn && !insn_len)) + return 1; + er = x86_emulate_instruction(vcpu, cr2, emulation_type, insn, insn_len); switch (er) { diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index cd0a94e12c2a..d6e62d41545d 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -2409,7 +2409,8 @@ static int pf_interception(struct vcpu_svm *svm) u64 error_code = svm->vmcb->control.exit_info_1; return kvm_handle_page_fault(&svm->vcpu, error_code, fault_address, - svm->vmcb->control.insn_bytes, + static_cpu_has(X86_FEATURE_DECODEASSISTS) ? + svm->vmcb->control.insn_bytes : NULL, svm->vmcb->control.insn_len, !npt_enabled); } -- 2.9.5