From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752709AbcBZL2i (ORCPT ); Fri, 26 Feb 2016 06:28:38 -0500 Received: from mail-pa0-f47.google.com ([209.85.220.47]:33720 "EHLO mail-pa0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751310AbcBZL2g convert rfc822-to-8bit (ORCPT ); Fri, 26 Feb 2016 06:28:36 -0500 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 9.2 \(3112\)) Subject: Re: [PATCH] KVM: x86: fix missed hardware breakpoints From: Nadav Amit In-Reply-To: <56D02C01.2040400@linux.intel.com> Date: Fri, 26 Feb 2016 03:28:33 -0800 Cc: Paolo Bonzini , Linux Kernel Mailing List , kvm , oleg@redhat.com, Nadav Amit , avagin@gmail.com, stable@vger.kernel.org Content-Transfer-Encoding: 8BIT Message-Id: <6DD9380A-1EF7-4226-9405-017D17859472@gmail.com> References: <1455879402-23009-1-git-send-email-pbonzini@redhat.com> <56D02C01.2040400@linux.intel.com> To: Xiao Guangrong X-Mailer: Apple Mail (2.3112) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Xiao Guangrong wrote: > On 02/19/2016 06:56 PM, Paolo Bonzini wrote: >> Sometimes when setting a breakpoint a process doesn't stop on it. >> This is because the debug registers are not loaded correctly on >> VCPU load. >> >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index 4244c2baf57d..f4891f2ece23 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -2752,6 +2752,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) >> } >> >> kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); >> + vcpu->arch.switch_db_regs |= KVM_DEBUGREG_RELOAD; > > Er, i do not understand how it works. The BP is enabled in this test case so > the debug registers are always reloaded before entering guest as > KVM_DEBUGREG_BP_ENABLED bit is always set on switch_db_regs. What did i miss? Note that KVM_DEBUGREG_BP_ENABLED does not have to be set, since kvm_update_dr7() is not called once the guest has KVM_DEBUGREG_WONT_EXIT. Nadav