From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH 2/3] KVM: x86: let reexecute_instruction work for tdp Date: Tue, 27 Nov 2012 11:13:11 +0800 Message-ID: <50B42FC7.2080805@linux.vnet.ibm.com> References: <50AAC77C.8040505@linux.vnet.ibm.com> <50AAC7CE.2050506@linux.vnet.ibm.com> <20121126223712.GA10634@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Avi Kivity , LKML , KVM To: Marcelo Tosatti Return-path: Received: from e28smtp01.in.ibm.com ([122.248.162.1]:33880 "EHLO e28smtp01.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755400Ab2K0DNY (ORCPT ); Mon, 26 Nov 2012 22:13:24 -0500 Received: from /spool/local by e28smtp01.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 27 Nov 2012 08:43:21 +0530 In-Reply-To: <20121126223712.GA10634@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: On 11/27/2012 06:37 AM, Marcelo Tosatti wrote: > On Tue, Nov 20, 2012 at 07:59:10AM +0800, Xiao Guangrong wrote: >> Currently, reexecute_instruction refused to retry all instructions. If >> nested npt is used, the emulation may be caused by shadow page, it can >> be fixed by dropping the shadow page >> >> Signed-off-by: Xiao Guangrong >> --- >> arch/x86/kvm/x86.c | 14 ++++++++------ >> 1 files changed, 8 insertions(+), 6 deletions(-) >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index 7be8452..5fe72cc 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -4469,17 +4469,19 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu) >> return r; >> } >> >> -static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t gva) >> +static bool reexecute_instruction(struct kvm_vcpu *vcpu, unsigned long cr2) >> { >> - gpa_t gpa; >> + gpa_t gpa = cr2; >> pfn_t pfn; >> >> - if (tdp_enabled) >> + if (!ACCESS_ONCE(vcpu->kvm->arch.indirect_shadow_pages)) >> return false; > > How is indirect_shadow_pages protected? Why is ACCESS_ONCE() being used > to read it? Hi Marcelo, It is protected by mmu-lock for it only be changed when mmu-lock is hold. And ACCESS_ONCE is used on read path avoiding magic optimization from compiler.