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Re: [Qemu-devel] [PATCH 3/4] spapr_iommu: Provide a function to switch a
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH 3/4] spapr_iommu: Provide a function to switch a TCE table to allowing VFIO |
Date: |
Thu, 1 Oct 2015 10:45:44 +1000 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Wed, Sep 30, 2015 at 12:07:39PM +0200, Thomas Huth wrote:
> On 30/09/15 05:48, David Gibson wrote:
> > Because of the way non-VFIO guest IOMMU operations are KVM accelerated, not
> > all TCE tables (guest IOMMU contexts) can support VFIO devices. Currently,
> > this is decided at creation time.
> >
> > To support hotplug of VFIO devices, we need to allow a TCE table which
> > previously didn't allow VFIO devices to be switched so that it can. This
> > patch adds an spapr_tce_set_need_vfio() function to do this, by
> > reallocating the table in userspace if necessary.
> >
> > Currently this doesn't allow the KVM acceleration to be re-enabled if all
> > the VFIO devices are removed. That's an optimization for another time.
> >
> > Signed-off-by: David Gibson <address@hidden>
> > ---
> > hw/ppc/spapr_iommu.c | 32 ++++++++++++++++++++++++++++++++
> > include/hw/ppc/spapr.h | 2 ++
> > 2 files changed, 34 insertions(+)
> >
> > diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
> > index 5166cde..8d60f8b 100644
> > --- a/hw/ppc/spapr_iommu.c
> > +++ b/hw/ppc/spapr_iommu.c
> > @@ -168,6 +168,38 @@ static int spapr_tce_table_realize(DeviceState *dev)
> > return 0;
> > }
> >
> > +void spapr_tce_set_need_vfio(sPAPRTCETable *tcet, bool need_vfio)
> > +{
> > + size_t table_size = tcet->nb_table * sizeof(uint64_t);
> > + void *newtable;
> > +
> > + if (need_vfio == tcet->need_vfio) {
> > + /* Nothing to do */
> > + return;
> > + }
> > +
> > + if (!need_vfio) {
> > + /* FIXME: We don't support transition back to KVM accelerated
> > + * TCEs yet */
> > + return;
> > + }
> > +
> > + tcet->need_vfio = true;
> > +
> > + if (tcet->fd < 0) {
> > + /* Table is already in userspace, nothing to be do */
> > + return;
> > + }
> > +
> > + newtable = g_malloc0(table_size);
>
> Since you immediately fill the whole table with the memcpy below, you do
> not need to zero the memory here, i.e. g_malloc instead of g_malloc0
> should be sufficient.
True, I just used malloc0 out of habit.
--
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
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- Re: [Qemu-devel] [PATCH 4/4] spapr_pci: Allow VFIO devices to work on the normal PCI host bridge, (continued)