Received-SPF: pass (google.com: domain of linux-kernel+bounces-170326-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Date: Mon, 6 May 2024 12:10:39 -0700
From: Isaku Yamahata <isaku.yamahata@intel.com>
To: Binbin Wu <binbin.wu@linux.intel.com>
Cc: isaku.yamahata@intel.com, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, isaku.yamahata@gmail.com,
	Paolo Bonzini <pbonzini@redhat.com>, erdemaktas@google.com,
	Sean Christopherson <seanjc@google.com>,
	Sagi Shahar <sagis@google.com>, Kai Huang <kai.huang@intel.com>,
	chen.bo@intel.com, hang.yuan@intel.com, tina.zhang@intel.com,
	Xiaoyao Li <xiaoyao.li@intel.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Chao Gao <chao.gao@intel.com>,
	Reinette Chatre <reinette.chatre@intel.com>,
	rick.p.edgecombe@intel.com
Subject: Re: [PATCH v19 088/130] KVM: x86: Add a switch_db_regs flag to
 handle TDX's auto-switched behavior
Message-ID: <20240506191039.GE13783@ls.amr.corp.intel.com>
References: <cover.1708933498.git.isaku.yamahata@intel.com>
 <ca5d0399cdbbaa6c7c6528ad85b3560cec0f0752.1708933498.git.isaku.yamahata@intel.com>
 <fdf2d5fa-64dc-4429-8529-66106632a95b@linux.intel.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <fdf2d5fa-64dc-4429-8529-66106632a95b@linux.intel.com>

On Mon, May 06, 2024 at 11:30:52AM +0800,
Binbin Wu <binbin.wu@linux.intel.com> wrote:

> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 1b189e86a1f1..fb7597c22f31 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -11013,7 +11013,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> >   	if (vcpu->arch.guest_fpu.xfd_err)
> >   		wrmsrl(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err);
> > -	if (unlikely(vcpu->arch.switch_db_regs)) {
> > +	if (unlikely(vcpu->arch.switch_db_regs & ~KVM_DEBUGREG_AUTO_SWITCH)) {
> 
> As pointed by Paolo in
> https://lore.kernel.org/lkml/ea136ac6-53cf-cdc5-a741-acfb437819b1@redhat.com/
> KVM_DEBUGREG_BP_ENABLED could be set in vcpu->arch.switch_db_regs,  by
> userspace
> kvm_vcpu_ioctl_x86_set_debugregs()  --> kvm_update_dr7()
> 
> So it should be fixed as:
> 
> -       if (unlikely(vcpu->arch.switch_db_regs)) {
> +       if (unlikely(vcpu->arch.switch_db_regs &&
> +                    !(vcpu->arch.switch_db_regs &
> KVM_DEBUGREG_AUTO_SWITCH))) {

Yes, that's true. Thanks for catching this.
-- 
Isaku Yamahata <isaku.yamahata@intel.com>