From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37946) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zdwbp-0004zy-Cu for qemu-devel@nongnu.org; Mon, 21 Sep 2015 04:38:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zdwbl-0004aa-SX for qemu-devel@nongnu.org; Mon, 21 Sep 2015 04:38:01 -0400 Received: from e06smtp07.uk.ibm.com ([195.75.94.103]:55998) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zdwbl-0004a7-Js for qemu-devel@nongnu.org; Mon, 21 Sep 2015 04:37:57 -0400 Received: from /spool/local by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 21 Sep 2015 09:37:56 +0100 Date: Mon, 21 Sep 2015 10:37:28 +0200 From: Greg Kurz Message-ID: <20150921103728.5524d0ce@bahia.local> In-Reply-To: <55FFBF4C.9030908@redhat.com> References: <1442479781-20164-1-git-send-email-thuth@redhat.com> <20150918110552.6487a506@bahia.local> <20150921021000.GI20331@voom.fritz.box> <20150921100157.3d6561aa@bahia.local> <55FFBF4C.9030908@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/X39zduMU29S2mugtvBs5D7R"; protocol="application/pgp-signature" Subject: Re: [Qemu-devel] [PATCH v4] ppc/spapr: Implement H_RANDOM hypercall in QEMU List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth Cc: qemu-devel@nongnu.org, kvm-ppc@vger.kernel.org, agraf@suse.de, michael@ellerman.id.au, qemu-ppc@nongnu.org, amit.shah@redhat.com, sam.bobroff@au1.ibm.com, David Gibson --Sig_/X39zduMU29S2mugtvBs5D7R Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Mon, 21 Sep 2015 10:26:52 +0200 Thomas Huth wrote: > On 21/09/15 10:01, Greg Kurz wrote: > > On Mon, 21 Sep 2015 12:10:00 +1000 > > David Gibson wrote: > >=20 > >> On Fri, Sep 18, 2015 at 11:05:52AM +0200, Greg Kurz wrote: > >>> On Thu, 17 Sep 2015 10:49:41 +0200 > >>> Thomas Huth wrote: > >>> > >>>> The PAPR interface defines a hypercall to pass high-quality > >>>> hardware generated random numbers to guests. Recent kernels can > >>>> already provide this hypercall to the guest if the right hardware > >>>> random number generator is available. But in case the user wants > >>>> to use another source like EGD, or QEMU is running with an older > >>>> kernel, we should also have this call in QEMU, so that guests that > >>>> do not support virtio-rng yet can get good random numbers, too. > >>>> > >>>> This patch now adds a new pseudo-device to QEMU that either > >>>> directly provides this hypercall to the guest or is able to > >>>> enable the in-kernel hypercall if available. > ... > >>> It is a good thing that the user can choose between in-kernel and bac= kend, > >>> and this patch does the work. > >>> > >>> This being said, I am not sure about the use case where a user has a = hwrng > >>> capable platform and wants to run guests without any hwrng support at= all is > >>> an appropriate default behavior... I guess we will find more users th= at want > >>> in-kernel being the default if it is available. > >>> > >>> The patch below modifies yours to do just this: the pseudo-device is = only > >>> created if hwrng is present and not already created. > >> > >> I have mixed feelings about this. On the one hand, I agree that it > >> would be nice to allow H_RANDOM support by default. On the other hand > >> the patch below leaves no way to turn it off for testing purposes. It > >> also adds another place where the guest hardware depends on the host > >> configuration, which adds to the already substantial mess of ensuring > >> that source and destination hardware configuration matches for > >> migration. > >=20 > > Yeah, describing the guest hw is really essential for migration... this > > is best addressed at the libvirt level with a full XML description of > > the machine... but FWIW if we are talking about running pseries on a > > POWER8 or newer host, I am not aware about "hwrng-less" boards... but > > I am probably missing something :) >=20 > Maybe it would be at least ok to enable it by default as long as > "-nodefaults" has not been specified as command line option? >=20 It makes a lot of sense indeed. I guess David should take your patch as it is now and the default behavior could be a follow up. > > Back to Thomas' patch, it does the job and brings H_RANDOM, which is > > currently missing. > >=20 > > Acked-by: Greg Kurz > >=20 > > I could test both use-kvm and backend flavors (including migration). > >=20 > > Tested-by: Greg Kurz >=20 > Thanks! >=20 > Thomas >=20 >=20 --Sig_/X39zduMU29S2mugtvBs5D7R Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEYEARECAAYFAlX/wcgACgkQAvw66wEB28KJ8gCfWhOQnw6kFp+fIXNWYvT5InkA tMkAoJ3y6JRo/IbzN7z7yvtg716lnKGf =LHyH -----END PGP SIGNATURE----- --Sig_/X39zduMU29S2mugtvBs5D7R--