RE: [PATCH v2] KVM: x86: enable dirty log gradually in small chunks

From: "Zhoujian (jay)" <jianjay.zhou@huawei.com>
To: Peter Xu <peterx@redhat.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"wangxin (U)" <wangxinxin.wang@huawei.com>,
	"Huangweidong (C)" <weidong.huang@huawei.com>,
	"Liujinsong (Paul)" <liu.jinsong@huawei.com>
Subject: RE: [PATCH v2] KVM: x86: enable dirty log gradually in small chunks
Date: Fri, 21 Feb 2020 09:43:52 +0000	[thread overview]
Message-ID: <B2D15215269B544CADD246097EACE7474BB0653E@DGGEMM528-MBX.china.huawei.com> (raw)
In-Reply-To: <20200220194229.GB15253@xz-x1>


> -----Original Message-----
> From: Peter Xu [mailto:peterx@redhat.com]
> Sent: Friday, February 21, 2020 3:42 AM
> To: Sean Christopherson <sean.j.christopherson@intel.com>
> Cc: Zhoujian (jay) <jianjay.zhou@huawei.com>; kvm@vger.kernel.org;
> pbonzini@redhat.com; wangxin (U) <wangxinxin.wang@huawei.com>;
> Huangweidong (C) <weidong.huang@huawei.com>; Liujinsong (Paul)
> <liu.jinsong@huawei.com>
> Subject: Re: [PATCH v2] KVM: x86: enable dirty log gradually in small chunks
> 
> On Thu, Feb 20, 2020 at 11:23:50AM -0800, Sean Christopherson wrote:
> > On Thu, Feb 20, 2020 at 02:17:06PM -0500, Peter Xu wrote:
> > > On Thu, Feb 20, 2020 at 12:28:28PM +0800, Jay Zhou wrote:
> > > > @@ -3348,7 +3352,14 @@ static int
> kvm_vm_ioctl_enable_cap_generic(struct kvm *kvm,
> > > >  	switch (cap->cap) {
> > > >  #ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
> > > >  	case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2:
> > > > -		if (cap->flags || (cap->args[0] & ~1))
> > > > +		if (cap->flags ||
> > > > +		    (cap->args[0] & ~KVM_DIRTY_LOG_MANUAL_CAPS) ||
> > > > +		    /* The capability of KVM_DIRTY_LOG_INITIALLY_SET
> depends
> > > > +		     * on KVM_DIRTY_LOG_MANUAL_PROTECT, it should not
> be
> > > > +		     * set individually
> > > > +		     */
> > > > +		    ((cap->args[0] & KVM_DIRTY_LOG_MANUAL_CAPS) ==
> > > > +			KVM_DIRTY_LOG_INITIALLY_SET))
> > >
> > > How about something easier to read? :)
> > >
> > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index
> > > 70f03ce0e5c1..9dfbab2a9929 100644
> > > --- a/virt/kvm/kvm_main.c
> > > +++ b/virt/kvm/kvm_main.c
> > > @@ -3348,7 +3348,10 @@ static int
> kvm_vm_ioctl_enable_cap_generic(struct kvm *kvm,
> > >         switch (cap->cap) {
> > >  #ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
> > >         case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2:
> > > -               if (cap->flags || (cap->args[0] & ~1))
> > > +               if (cap->flags || (cap->args[0] & ~3))
> > > +                       return -EINVAL;
> > > +               /* Allow 00, 01, and 11. */
> > > +               if (cap->args[0] == KVM_DIRTY_LOG_INITIALLY_SET)
> > >                         return -EINVAL;
> >
> > Oof, "easier" is subjective :-)  How about this?
> >
> > 	case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2: {
> > 		u64 allowed_options = KVM_DIRTY_LOG_MANUAL_PROTECT;
> >
> > 		if (cap->args[0] & KVM_DIRTY_LOG_MANUAL_PROTECT)
> > 			allowed_options = KVM_DIRTY_LOG_INITIALLY_SET;

I believe you mean

		if (cap->args[0] & KVM_DIRTY_LOG_MANUAL_PROTECT)
			allowed_options |= KVM_DIRTY_LOG_INITIALLY_SET;

?

> >
> > 		if (cap->flags || (cap->args[0] & ~allowed_options))
> > 			return -EINVAL;
> > 		kvm->manual_dirty_log_protect = cap->args[0];
> > 		return 0;
> > 	}
> 
> Fine by me! (But I won't tell I still prefer mine ;)

:-)


Regards,
Jay Zhou

> 
> --
> Peter Xu