Re: [Xen-devel] [PATCH v7 3/6] iommu: make iommu_inclusive_mapping a suboption of dom0-iommu

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 22/08/18 16:22, Roger Pau Monné wrote:
> On Wed, Aug 22, 2018 at 04:07:26PM +0100, Julien Grall wrote:
> > Hi Roger,
> >
> > On 22/08/18 08:51, Roger Pau Monne wrote:
> > > Introduce a new dom0-iommu=map-inclusive generic option that
> > > supersedes iommu_inclusive_mapping. The previous behavior is preserved
> > > and the option should only be enabled by default on Intel hardware.
> > >
> > > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > > Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> > > Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> > > Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> > > ---
> > > Changes since v4:
> > >    - Use an if to set the default option value.
> > >    - Set the option to false unconditionally on ARM.
> > >
> > > Changes since v2:
> > >    - Fix typo in commit message.
> > >    - Change style and text of the documentation in xen command line.
> > >    - Set the defaults in {intel/amd}_iommu_hwdom_init for inclusive.
> > >    - Re-add the iommu_dom0_passthrough || !is_pv_domain(d) check.
> > >
> > > Changes since v1:
> > >    - Use dom0-iommu instead of the iommu option.
> > >    - Only enable by default on Intel hardware.
> > > ---
> > > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > > Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> > > Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> > > Cc: Jan Beulich <jbeulich@xxxxxxxx>
> > > Cc: Julien Grall <julien.grall@xxxxxxx>
> > > Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > > Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > > Cc: Tim Deegan <tim@xxxxxxx>
> > > Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> > > Cc: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> > > Cc: Brian Woods <brian.woods@xxxxxxx>
> > > Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
> > > ---
> > >    docs/misc/xen-command-line.markdown         | 13 ++++-
> > >    xen/drivers/passthrough/amd/pci_amd_iommu.c |  4 ++
> > >    xen/drivers/passthrough/arm/iommu.c         |  4 ++
> > >    xen/drivers/passthrough/arm/smmu.c          |  2 +
> > >    xen/drivers/passthrough/iommu.c             | 12 +++++
> > >    xen/drivers/passthrough/vtd/extern.h        |  2 -
> > >    xen/drivers/passthrough/vtd/iommu.c         |  8 ++-
> > >    xen/drivers/passthrough/vtd/x86/vtd.c       | 58 +-------------------
> > >    xen/drivers/passthrough/x86/iommu.c         | 59 +++++++++++++++++++++
> > >    xen/include/xen/iommu.h                     |  2 +
> > >    10 files changed, 99 insertions(+), 65 deletions(-)
> > >
> > > diff --git a/docs/misc/xen-command-line.markdown 
> > > b/docs/misc/xen-command-line.markdown
> > > index cd57960ede..98f0f3b68b 100644
> > > --- a/docs/misc/xen-command-line.markdown
> > > +++ b/docs/misc/xen-command-line.markdown
> > > @@ -682,7 +682,7 @@ Flag that makes a dom0 use shadow paging. Only works when 
> > > "pvh" is
> > >    enabled.
> > >    ### dom0-iommu
> > > -> `= List of [ passthrough | strict ]`
> > > +> `= List of [ passthrough | strict | map-inclusive ]`
> > >    This list of booleans controls the iommu usage by Dom0:
> > > @@ -696,6 +696,14 @@ This list of booleans controls the iommu usage by Dom0:
> > >      `true` for a PVH Dom0 and any attempt to overwrite it from the command line
> > >      is ignored.
> > > +* `map-inclusive`: sets up DMA remapping for all the non-RAM regions below 4GB
> > > +  except for unusable ranges. Use this to work around firmware issues providing
> > > +  incorrect RMRR/IVMD entries. Rather than only mapping RAM pages for IOMMU
> > > +  accesses for Dom0, with this option all pages up to 4GB, not marked as
> > > +  unusable in the E820 table, will get a mapping established. Note that this
> > > +  option is only applicable to a PV Dom0 and is enabled by default on Intel
> > > +  hardware.
> > > +
> > >    ### dom0\_ioports\_disable (x86)
> > >    > `= List of <hex>-<hex>`
> > > @@ -1233,6 +1241,9 @@ wait descriptor timed out', try increasing this value.
> > >    ### iommu\_inclusive\_mapping (VT-d)
> > >    > `= <boolean>`
> > > +**WARNING: This command line option is deprecated, and superseded by
> > > +_dom0-iommu=map-inclusive_ - using both options in combination is undefined.**
> > > +
> > >    > Default: `true`
> > >    Use this to work around firmware issues providing incorrect RMRR entries.
> > > diff --git a/xen/drivers/passthrough/amd/pci_amd_iommu.c 
> > > b/xen/drivers/passthrough/amd/pci_amd_iommu.c
> > > index ab39e7500d..27eb49619d 100644
> > > --- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
> > > +++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
> > > @@ -253,6 +253,10 @@ static void __hwdom_init amd_iommu_hwdom_init(struct 
> > > domain *d)
> > >        unsigned long i;
> > >        const struct amd_iommu *iommu;
> > > +    /* Inclusive IOMMU mappings are disabled by default on AMD hardware. */
> > > +    if ( iommu_hwdom_inclusive == -1 )
> > > +        iommu_hwdom_inclusive = false;
> > This is a quite bad practice to mix boolean and integer. Can you please
> > rework the code to avoid that?
> I don't think I can fix that. An integer is used so that the default
> value is set to -1. Then at runtime a default value based on the
> hardware is set unless the user has already specified a value on the
> command line.
>
> It needs to be a tristate in order to detect whether the user has
> specified a value on the command line.
In that case the solution is to use -1, 0, 1. So replacing false with 0 
and true with 1.
Cheers,

--
Julien Grall

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