Re: [PATCH] kvm_s390_vm_start_migration: check dirty_bitmap before using it as target for memset()

From: Claudio Imbrenda <imbrenda@linux.ibm.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Igor Mammedov <imammedo@redhat.com>,
	linux-kernel@vger.kernel.org, david@redhat.com,
	cohuck@redhat.com, Janosch Frank <frankja@linux.ibm.com>
Subject: Re: [PATCH] kvm_s390_vm_start_migration: check dirty_bitmap before using it as target for memset()
Date: Tue, 10 Sep 2019 12:21:12 +0200	[thread overview]
Message-ID: <20190910122112.098e3494@p-imbrenda.boeblingen.de.ibm.com> (raw)
In-Reply-To: <4668e4e9-c0bc-3647-6387-20c6f8107ed3@de.ibm.com>

On Mon, 9 Sep 2019 18:21:47 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

[...]

> > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > index f329dcb3f44c..dfba51c9d60c 100644
> > --- a/arch/s390/kvm/kvm-s390.c
> > +++ b/arch/s390/kvm/kvm-s390.c
> > @@ -1018,6 +1018,10 @@ static int
> > kvm_s390_vm_start_migration(struct kvm *kvm) /* mark all the pages
> > in active slots as dirty */ for (slotnr = 0; slotnr <
> > slots->used_slots; slotnr++) { ms = slots->memslots + slotnr;
> > +		if (!ms->dirty_bitmap) {
> > +			WARN(1, "ms->dirty_bitmap == NULL\n");  
> 
> I would prefer to not have a WARN_ON. Otherwise this would allow a
> malicious user to spam the log. 

I agree, the WARN is not needed.

> 
> > +			return -EINVAL;
> > +		}
> >  		/*
> >  		 * The second half of the bitmap is only used on
> > x86,
> >  		 * and would be wasted otherwise, so we put it to
> > good 

Otherwise it looks good.

Claudio Imbrenda