From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50641) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WYJp8-0000Fe-Dw for qemu-devel@nongnu.org; Thu, 10 Apr 2014 14:35:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WYJp2-0002Db-I3 for qemu-devel@nongnu.org; Thu, 10 Apr 2014 14:35:42 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:46470) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WYJp2-0002DL-9x for qemu-devel@nongnu.org; Thu, 10 Apr 2014 14:35:36 -0400 Date: Thu, 10 Apr 2014 13:47:09 -0500 From: Serge Hallyn Message-ID: <20140410184708.GA3352@ac100> References: <20140409032106.GA5163@sergelap> <5346C71D.6070606@msgid.tls.msk.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5346C71D.6070606@msgid.tls.msk.ru> Subject: Re: [Qemu-devel] [PATCH 1/1] kvm_physical_sync_dirty_bitmap: ignore ENOENT from kvm_vm_ioctl List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Michael Tokarev Cc: qemu-devel@nongnu.org, 1303926@bugs.launchpad.net, Mario Smarduch Quoting Michael Tokarev (mjt@tls.msk.ru): > 09.04.2014 07:21, Serge Hallyn wrote: > > ENOENT (iiuc) means the kernel has an empty dirty bitmap for this > > slot. Don't abort in that case. This appears to solve the bug > > reported at > > > > https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1303926 > > > > which first showed up with commit b533f658a98325d: fix return check for > > KVM_GET_DIRTY_LOG ioctl > > > > Signed-off-by: Serge Hallyn > > --- > > kvm-all.c | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > diff --git a/kvm-all.c b/kvm-all.c > > index 82a9119..7b7ea8d 100644 > > --- a/kvm-all.c > > +++ b/kvm-all.c > > @@ -441,10 +441,13 @@ static int kvm_physical_sync_dirty_bitmap(MemoryRegionSection *section) > > > > d.slot = mem->slot; > > > > - if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) == -1) { > > + ret = kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d); > > + if (ret < 0 && ret != -ENOENT) { > > DPRINTF("ioctl failed %d\n", errno); > > ret = -1; > > break; > > + } else if (ret < 0) { > > + ret = 0; > > } > > > > kvm_get_dirty_pages_log_range(section, d.dirty_bitmap); > > Should we omit calling kvm_get_dirty_pages_log_range() if there's > no bitmap from kernel? If that's something we can know then certainly that'll be better. It'll save an ioctl and copy_from_user of the whole of &d. > In particular, do we trust kernel to not > touch d.dirty_bitmap when it returns ENOENT? Seems ok, kvm_vm_ioctl_get_dirty_log() doesn't change anything in *log before returning when it finds no dirty_mapslot. -serge