Re: [PATCH 1/6] xen: extend XEN_DOMCTL_memory_mapping to handle cacheability

[Stefano Stabellini <sstabellini@kernel.org>]

On Wed, 27 Feb 2019, Julien Grall wrote:
> Hi Stefano,
> 
> On 2/26/19 11:07 PM, Stefano Stabellini wrote:
> > Reuse the existing padding field to pass cacheability information about
> > the memory mapping, specifically, whether the memory should be mapped as
> > normal memory or as device memory (this is what we have today).
> > 
> > Add a cacheability parameter to map_mmio_regions. 0 means device
> > memory, which is what we have today.
> > 
> > On ARM, map device memory as p2m_mmio_direct_dev (as it is already done
> > today) and normal memory as p2m_ram_rw.
> > 
> > On x86, return error if the cacheability requested is not device memory.
> > 
> > Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>
> > CC: JBeulich@suse.com
> > CC: andrew.cooper3@citrix.com
> > ---
> >   xen/arch/arm/gic-v2.c            |  3 ++-
> >   xen/arch/arm/p2m.c               | 19 +++++++++++++++++--
> >   xen/arch/arm/platforms/exynos5.c |  4 ++--
> >   xen/arch/arm/platforms/omap5.c   |  8 ++++----
> >   xen/arch/arm/vgic-v2.c           |  2 +-
> >   xen/arch/arm/vgic/vgic-v2.c      |  2 +-
> >   xen/arch/x86/hvm/dom0_build.c    |  7 +++++--
> >   xen/arch/x86/mm/p2m.c            |  6 +++++-
> >   xen/common/domctl.c              |  8 +++++---
> >   xen/drivers/vpci/header.c        |  3 ++-
> >   xen/include/public/domctl.h      |  4 +++-
> >   xen/include/xen/p2m-common.h     |  3 ++-
> >   12 files changed, 49 insertions(+), 20 deletions(-)
> > 
> > diff --git a/xen/arch/arm/gic-v2.c b/xen/arch/arm/gic-v2.c
> > index e7eb01f..1ea3da2 100644
> > --- a/xen/arch/arm/gic-v2.c
> > +++ b/xen/arch/arm/gic-v2.c
> > @@ -690,7 +690,8 @@ static int gicv2_map_hwdown_extra_mappings(struct domain
> > *d)
> >             ret = map_mmio_regions(d, gaddr_to_gfn(v2m_data->addr),
> >                                  PFN_UP(v2m_data->size),
> > -                               maddr_to_mfn(v2m_data->addr));
> > +                               maddr_to_mfn(v2m_data->addr),
> > +                               CACHEABILITY_DEVMEM);
> >           if ( ret )
> >           {
> >               printk(XENLOG_ERR "GICv2: Map v2m frame to d%d failed.\n",
> > diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> > index 30cfb01..5b8fcc5 100644
> > --- a/xen/arch/arm/p2m.c
> > +++ b/xen/arch/arm/p2m.c
> > @@ -1068,9 +1068,24 @@ int unmap_regions_p2mt(struct domain *d,
> >   int map_mmio_regions(struct domain *d,
> >                        gfn_t start_gfn,
> >                        unsigned long nr,
> > -                     mfn_t mfn)
> > +                     mfn_t mfn,
> > +                     uint32_t cache_policy)
> 
> Rather than extending map_mmio_regions, I would prefer if we kill this
> function (and unmap_mmio_mmio_regions) and instead use map_regions_p2mt.
> 
> This means the conversation to p2mt should be done in the DOMCTL handling.

map_regions_p2mt is an arm specific function. map_mmio_regions is the
common function across x86 and arm, called from common code.


> >   {
> > -    return p2m_insert_mapping(d, start_gfn, nr, mfn, p2m_mmio_direct_dev);
> > +    p2m_type_t t;
> > +
> > +    switch ( cache_policy )
> > +    {
> > +    case CACHEABILITY_MEMORY:
> > +        t = p2m_ram_rw;
> > +        break;
> > +    case CACHEABILITY_DEVMEM:
> > +        t = p2m_mmio_direct_dev;
> > +        break;
> > +    default:
> > +        return -ENOSYS;
> 
> We tend to use EOPNOTSUPP in such a case.

Yes, OK

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