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Wed, 25 Mar 2020 11:15:46 -0700 (PDT) Date: Wed, 25 Mar 2020 14:15:43 -0400 From: Peter Xu To: "Dr. David Alan Gilbert" Subject: Re: [PATCH RFC 5/9] KVM: Provide helper to get kvm dirty log Message-ID: <20200325181543.GA404034@xz-x1> References: <20200205141749.378044-1-peterx@redhat.com> <20200205141749.378044-6-peterx@redhat.com> <20200325175220.GD2635@work-vm> MIME-Version: 1.0 In-Reply-To: <20200325175220.GD2635@work-vm> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 216.205.24.74 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , qemu-devel@nongnu.org, "Michael S . Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Mar 25, 2020 at 05:52:20PM +0000, Dr. David Alan Gilbert wrote: > * Peter Xu (peterx@redhat.com) wrote: > > Provide a helper kvm_slot_get_dirty_log() to make the function > > kvm_physical_sync_dirty_bitmap() clearer. We can even cache the as_id > > into KVMSlot when it is created, so that we don't even need to pass it > > down every time. > >=20 > > Since at it, remove return value of kvm_physical_sync_dirty_bitmap() > > because it should never fail. > >=20 > > Signed-off-by: Peter Xu > > --- > > accel/kvm/kvm-all.c | 39 +++++++++++++++++++-------------------- > > include/sysemu/kvm_int.h | 2 ++ > > 2 files changed, 21 insertions(+), 20 deletions(-) > >=20 > > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c > > index bb635c775f..608216fd53 100644 > > --- a/accel/kvm/kvm-all.c > > +++ b/accel/kvm/kvm-all.c > > @@ -553,6 +553,18 @@ static void kvm_slot_init_dirty_bitmap(KVMSlot *me= m) > > mem->dirty_bmap =3D g_malloc0(bitmap_size); > > } > > =20 > > +/* Sync dirty bitmap from kernel to KVMSlot.dirty_bmap */ > > +static void kvm_slot_get_dirty_log(KVMState *s, KVMSlot *slot) > > +{ > > + struct kvm_dirty_log d =3D {}; > > + int ret; > > + > > + d.dirty_bitmap =3D slot->dirty_bmap; > > + d.slot =3D slot->slot | (slot->as_id << 16); > > + ret =3D kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d); > > + assert(ret !=3D -1); >=20 > As discussed on irc, that -1 check seems odd given your previous check > but there seems to be some history as to why it was still there. Hmm. >=20 > It also seems very trusting that it can never possibly fail! Yeah I agree. I've asked the question under patch 1. Before we know the answer, I'll remove the assertion to print an error if it triggers; check against -1 (-EPERM) explicitly does look odd... Thanks, --=20 Peter Xu