From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53892) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1avJ76-0000Co-Ah for qemu-devel@nongnu.org; Wed, 27 Apr 2016 02:38:21 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1avJ74-0000y7-Eu for qemu-devel@nongnu.org; Wed, 27 Apr 2016 02:38:20 -0400 Date: Wed, 27 Apr 2016 16:39:31 +1000 From: David Gibson Message-ID: <20160427063931.GF18476@voom.redhat.com> References: <1459762426-18440-1-git-send-email-aik@ozlabs.ru> <1459762426-18440-15-git-send-email-aik@ozlabs.ru> <20160407004056.GE16485@voom.fritz.box> <571748A3.4070105@ozlabs.ru> <20160421035954.GH1133@voom> <57185569.3070405@ozlabs.ru> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="NGIwU0kFl1Z1A3An" Content-Disposition: inline In-Reply-To: <57185569.3070405@ozlabs.ru> Subject: Re: [Qemu-devel] [PATCH qemu v15 14/17] spapr_iommu, vfio, memory: Notify IOMMU about starting/stopping being used by VFIO List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexey Kardashevskiy Cc: qemu-devel@nongnu.org, qemu-ppc@nongnu.org, Alex Williamson , Alexander Graf --NGIwU0kFl1Z1A3An Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Apr 21, 2016 at 02:22:01PM +1000, Alexey Kardashevskiy wrote: > On 04/21/2016 01:59 PM, David Gibson wrote: > >On Wed, Apr 20, 2016 at 07:15:15PM +1000, Alexey Kardashevskiy wrote: > >>On 04/07/2016 10:40 AM, David Gibson wrote: > >>>On Mon, Apr 04, 2016 at 07:33:43PM +1000, Alexey Kardashevskiy wrote: > >>>>The sPAPR TCE tables manage 2 copies when VFIO is using an IOMMU - > >>>>a guest view of the table and a hardware TCE table. If there is no VF= IO > >>>>presense in the address space, then just the guest view is used, if > >>>>this is the case, it is allocated in the KVM. However since there is = no > >>>>support yet for VFIO in KVM TCE hypercalls, when we start using VFIO, > >>>>we need to move the guest view from KVM to the userspace; and we need > >>>>to do this for every IOMMU on a bus with VFIO devices. > >>>> > >>>>This adds vfio_start/vfio_stop callbacks in MemoryRegionIOMMUOps to > >>>>notifiy IOMMU about changing environment so it can reallocate the tab= le > >>>>to/from KVM or (when available) hook the IOMMU groups with the logical > >>>>bus (LIOBN) in the KVM. > >>>> > >>>>This removes explicit spapr_tce_set_need_vfio() call from PCI hotplug > >>>>path as the new callbacks do this better - they notify IOMMU at > >>>>the exact moment when the configuration is changed, and this also > >>>>includes the case of PCI hot unplug. > >>>> > >>>>As there can be multiple containers attached to the same PHB/LIOBN, > >>>>this replaces the @need_vfio flag in sPAPRTCETable with the counter > >>>>of VFIO users. > >>>> > >>>>Signed-off-by: Alexey Kardashevskiy > >>> > >>>This looks correct, but there's one remaining ugly. > >>> > >>>>--- > >>>>Changes: > >>>>v15: > >>>>* s/need_vfio/vfio-Users/g > >>>>--- > >>>> hw/ppc/spapr_iommu.c | 30 ++++++++++++++++++++---------- > >>>> hw/ppc/spapr_pci.c | 6 ------ > >>>> hw/vfio/common.c | 9 +++++++++ > >>>> include/exec/memory.h | 4 ++++ > >>>> include/hw/ppc/spapr.h | 2 +- > >>>> 5 files changed, 34 insertions(+), 17 deletions(-) > >>>> > >>>>diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c > >>>>index c945dba..ea09414 100644 > >>>>--- a/hw/ppc/spapr_iommu.c > >>>>+++ b/hw/ppc/spapr_iommu.c > >>>>@@ -155,6 +155,16 @@ static uint64_t spapr_tce_get_page_sizes(MemoryR= egion *iommu) > >>>> return 1ULL << tcet->page_shift; > >>>> } > >>>> > >>>>+static void spapr_tce_vfio_start(MemoryRegion *iommu) > >>>>+{ > >>>>+ spapr_tce_set_need_vfio(container_of(iommu, sPAPRTCETable, iommu= ), true); > >>>>+} > >>>>+ > >>>>+static void spapr_tce_vfio_stop(MemoryRegion *iommu) > >>>>+{ > >>>>+ spapr_tce_set_need_vfio(container_of(iommu, sPAPRTCETable, iommu= ), false); > >>>>+} > >>>>+ > >>>> static void spapr_tce_table_do_enable(sPAPRTCETable *tcet); > >>>> static void spapr_tce_table_do_disable(sPAPRTCETable *tcet); > >>>> > >>>>@@ -239,6 +249,8 @@ static const VMStateDescription vmstate_spapr_tce= _table =3D { > >>>> static MemoryRegionIOMMUOps spapr_iommu_ops =3D { > >>>> .translate =3D spapr_tce_translate_iommu, > >>>> .get_page_sizes =3D spapr_tce_get_page_sizes, > >>>>+ .vfio_start =3D spapr_tce_vfio_start, > >>>>+ .vfio_stop =3D spapr_tce_vfio_stop, > >>> > >>>Ok, so AFAICT these callbacks are called whenever a VFIO context is > >>>added / removed from the gIOMMU's address space, and it's up to the > >>>gIOMMU code to ref count that to see if there are any current vfio > >>>users. That makes "vfio_start" and "vfio_stop" not great names. > >>> > >>>But.. better than changing the names would be to move the refcounting > >>>to the generic code if you can manage it, so the individual gIOMMU > >>>backends don't need to - they just told when they need to start / stop > >>>providing VFIO support. > >> > >>Everything is manageable... > >> > >>This referencing is needed for the case of >=3D2 containers so > >>2xvfio_listener_region_add will create 2xVFIOGuestIOMMU as they are per > >>VFIOContainer so VFIOGuestIOMMU is not the right place for the reference > >>counting, VFIOAddressSpace seems to be that place (=3D> add list of IOM= MU MRs > >>with refcounter). Or even IOMMU MR. Or move VFIOGuestIOMMU list from > >>VFIOContainer to VFIOAddressSpace and then gIOMMU can handle > >>refcounting? > > > >I'm having a lot of trouble parsing that. I think the ref parsing has > >to be per-giommu (because individual giommus could, in theory, be > >mapped or unmapped from an address space). >=20 >=20 > Example 1. > POWER8, no DDW, one QEMU PHB, 2 IOMMU groups, table sharing so just 1 > container, one TCE table (aka gIOMMU), one TCE table in KVM, no reference > counting needed at all, simple. >=20 > Example 2. > POWER7, no DDW, one QEMU PHB, 2 IOMMU groups, no table sharing so there a= re > 2 containers but still one IOMMU MR which is added to each container so > there are 2 gIOMMU objects. And there is still one TCE table in KVM (which > is a guest view). Where do I put the reference counter which will count t= hat > there are 2 gIOMMUs per KVM TCE table in this example? Ah.. I'd forgotten that the gIOMMU object is per guest IOMMU window *and* per container, not just per guest IOMMU window. Ultimately it's the code implementing the guest side IOMMU which needs to know if it is supporting VFIO or not, so in generic terms that means per IOMMU-type MemoryRegion. Essentially you need to count the number of VFIOGuestIOMMU objects associated with each (gIOMMU) MemoryRegion, and notify the MemoryRegion if that changes from zero to non-zero or vice versa. I'd prefer if we can maintain that count from just the VFIO code and just notify the gIOMMU code on zero / non-zero changes. But I guess we'd need approval from Paolo to add that count to the MemoryRegion. The fallback would be similar to what you have - instead the MemoryRegion gets notified whenever a VFIOGuestIOMMU is attached or removed, and the MR (i.e. the guest side IOMMU code) has to maintain the count itself. --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson --NGIwU0kFl1Z1A3An Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJXIF6jAAoJEGw4ysog2bOSptsP/jrWW7OKPPyrlXdXoUY5fJgx 9KGCYbRdHi9O8jYNsRNlzL6IS4PP9rp0G6KNGJBbd93Id7/jhgx6JlB6KWk7vlut wTmytO+ltJj7+2L5vAFKJJfb9fUQgN2RkYthF0TCmFQc1j0sGitZjnPA9+3q1Fza lXVU6DxjadXHFa/47pVJchZn5eOliOfiFtEAhYhr6Vj/+zHNmgC6bNDTj41L8JWg t00Ei9nw61EPaEMxX/Pjel5pjxHj5GPlyFM1upevaVJYrGdl03akEGlXm+9WWwK2 3peQVMzXBC1DxrxYh2TWFjOrd8/1qW4Ohwhk+eYMYesDxLkNzHCUVh+mk8W2hozx CqBAtwn8qQB/qVXBDjJPQqiB1B92eTkIlrhHk0zfOHXnP9E+vtHbJmLMS+MyyLMQ OGiRQrf7U39la37PgfohDNWF+1ReBpd1k2adnmd57sbv7r0OH+HcKNO5TD3/KBh0 rG8YPfo7QMTwXvzq0T2SJ4qNgybjp5WXoe6EGbyrx9RD7xeQLFnL+ayhXDumkuRJ e+7RYvMLgrUchE+bCh2XWXVl+YnXqcc/m4ALxpSUW6qEUCQPvMrbt+WXF4vfTTdt W4942U0Z0VGp1EVn8337AdnBuOHRc6e83s0KUFwHL5OXpdJDw05TpIxRDPNPlt7H WTtOp3yZrwsZ1hZcbLGj =h1uG -----END PGP SIGNATURE----- --NGIwU0kFl1Z1A3An--