From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751580AbdINPko (ORCPT ); Thu, 14 Sep 2017 11:40:44 -0400 Received: from mx2.suse.de ([195.135.220.15]:49540 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751463AbdINPkl (ORCPT ); Thu, 14 Sep 2017 11:40:41 -0400 Date: Thu, 14 Sep 2017 17:40:32 +0200 From: Borislav Petkov To: Brijesh Singh Cc: linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org, Thomas Gleixner , Joerg Roedel , "Michael S . Tsirkin" , Paolo Bonzini , =?utf-8?B?XCJSYWRpbSBLcsSNbcOhxZlcIg==?= , Tom Lendacky Subject: Re: [RFC Part2 PATCH v3 26/26] KVM: X86: Restart the guest when insn_len is zero and SEV is enabled Message-ID: <20170914154032.mvrwjblf3sz4sibi@pd.tnic> References: <20170724200303.12197-1-brijesh.singh@amd.com> <20170724200303.12197-27-brijesh.singh@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170724200303.12197-27-brijesh.singh@amd.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 24, 2017 at 03:03:03PM -0500, Brijesh Singh wrote: > On AMD platform, under certain conditions insn_len may be zero on #NPF. "On AMD platforms... " > This can happen if guest gets a page-fault on data access, but HW table " ... if a guest... .. but the HW table walker ..." > walker is not able to read the instruction page (e.g instuction 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. Same question as in the previous patch: should we make this a proper interface? > I have encountered this issue when running kernbench inside the guest. > > 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 ccb70b8..be41ad0 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -4850,6 +4850,23 @@ 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 platform, under certain conditions insn_len may be zero on #NPF. Same typos as above. > + * This can happen if guest gets a page-fault on data access, but HW table > + * walker is not able to read the instruction page (e.g instuction page > + * is not present). > + * > + * Typically, when insn_len is zero, x86_emulate_instruction() walks the > + * guest page table and fetches the instruction bytes. When SEV is active, > + * the guest memory is encrypted with guest key hence we will not able to > + * fetch the instruction bytes. In those cases we simply restart the guest. > + */ > + if (unlikely(!insn_len)) { > + if (kvm_x86_ops->memory_encryption_enabled && > + kvm_x86_ops->memory_encryption_enabled(vcpu)) Align vertically. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --