From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752011AbdISUrg (ORCPT ); Tue, 19 Sep 2017 16:47:36 -0400 Received: from mail-by2nam01on0052.outbound.protection.outlook.com ([104.47.34.52]:32170 "EHLO NAM01-BY2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751884AbdISUr0 (ORCPT ); Tue, 19 Sep 2017 16:47:26 -0400 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=brijesh.singh@amd.com; From: Brijesh Singh To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: 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 Subject: [Part2 PATCH v4 28/29] KVM: X86: Restart the guest when insn_len is zero and SEV is enabled Date: Tue, 19 Sep 2017 15:46:26 -0500 Message-Id: <20170919204627.3875-29-brijesh.singh@amd.com> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20170919204627.3875-1-brijesh.singh@amd.com> References: <20170919204627.3875-1-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: CY4PR04CA0071.namprd04.prod.outlook.com (10.171.243.164) To SN1PR12MB0158.namprd12.prod.outlook.com (10.162.3.145) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: c81c544b-c297-4cd0-1662-08d4ff9f9f75 X-MS-Office365-Filtering-HT: Tenant X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(300000500095)(300135000095)(300000501095)(300135300095)(22001)(300000502095)(300135100095)(2017030254152)(48565401081)(300000503095)(300135400095)(2017052603199)(201703131423075)(201703031133081)(201702281549075)(300000504095)(300135200095)(300000505095)(300135600095)(300000506095)(300135500095);SRVR:SN1PR12MB0158; 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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 | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index eca30c1eb1d9..2bc0fe84aca2 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -4953,6 +4953,23 @@ 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). + * + * 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. + */ + if (unlikely(!insn_len) && + kvm_x86_ops->mem_enc_enabled && + kvm_x86_ops->mem_enc_enabled(vcpu)) + return 1; + er = x86_emulate_instruction(vcpu, cr2, emulation_type, insn, insn_len); switch (er) { -- 2.9.5