From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33977) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZdwRD-0008D4-K9 for qemu-devel@nongnu.org; Mon, 21 Sep 2015 04:27:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZdwR9-0007YZ-Kq for qemu-devel@nongnu.org; Mon, 21 Sep 2015 04:27:03 -0400 References: <1442479781-20164-1-git-send-email-thuth@redhat.com> <20150918110552.6487a506@bahia.local> <20150921021000.GI20331@voom.fritz.box> <20150921100157.3d6561aa@bahia.local> From: Thomas Huth Message-ID: <55FFBF4C.9030908@redhat.com> Date: Mon, 21 Sep 2015 10:26:52 +0200 MIME-Version: 1.0 In-Reply-To: <20150921100157.3d6561aa@bahia.local> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="LIQAp4Nxumkb1k1awO5tk5Ge116ebH9EW" 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: Greg Kurz , David Gibson Cc: agraf@suse.de, kvm-ppc@vger.kernel.org, qemu-devel@nongnu.org, michael@ellerman.id.au, qemu-ppc@nongnu.org, amit.shah@redhat.com, sam.bobroff@au1.ibm.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --LIQAp4Nxumkb1k1awO5tk5Ge116ebH9EW Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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. =2E.. >>> 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 :) Maybe it would be at least ok to enable it by default as long as "-nodefaults" has not been specified as command line option? > 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 Thanks! Thomas --LIQAp4Nxumkb1k1awO5tk5Ge116ebH9EW Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJV/79MAAoJEC7Z13T+cC21qikP/i0aSv5TCONdt0qkyXIYpihu eEgaFICK4+MOMSGb27fKDcANpYI6TmRJIuUDEYf06bdPi2+p0rOx5VIsf1y71buw GwZUGjLJDCaWdp96D+rc4cHnP1lxoxAu4s/xlNQL3+BqQYOJslk2+Tv40pbLvpe9 xYcLLOD1NnmlpTExbKvOCii5p2aJ382/czlNe1H/ZPYepmuqp19WxxhrntcRkXeL wPOAZoi9G3hOzTnmVgyEAq6E8SwutjlIIjpt5kZqv/+0hpN/zhRIMH+e/+K6FARJ qmxTd8Lt53KP8JgVk5YB3WFdkPZT9k0NSjrdYwCSdacUEUr1JQlVBW2Xxljwxp1F DfYuQUS2M0LWC0VTc+c+wcNfzj3EXnyVVZrW20kPsrqO6hyCFW/47/DwpCBz0LRB sfFY5ZoZdl1FDyhfVu7qRmkj2vM7byqGooamCdnPtGh9yjTIzn7W6POB0whG+LfU FHZnVMP/jHh5UorDhKYlVPP9XgHNii57TOe8BwvKCXLvQFPs7TvLPiyhAc0AA6FB Jqdoh3xChVk7qG0Ioit0OQ/KhsRMeCNC1t0kHlmeM3R34WwyxXyxJiL95gdzudI+ 9XOMY3eordjbNIAv7A+oEngPgl5mU0a9R8jSm/ekwr/iNdBoeHo83RFbjz0FKJ0Y fdcP/2QQ+NxfA8l0TdVj =6Sxg -----END PGP SIGNATURE----- --LIQAp4Nxumkb1k1awO5tk5Ge116ebH9EW--