Re: [Xen-devel] [PATCH v8 5/6] iommu: tidy up iommu_use_hap_pt() and need_iommu_pt_sync() macros

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Julien Grall <julien.grall@xxxxxxx>
> Sent: 05 September 2019 20:38
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Jan Beulich <jbeulich@xxxxxxxx>; Andrew Cooper 
> <Andrew.Cooper3@xxxxxxxxxx>; George Dunlap
> <George.Dunlap@xxxxxxxxxx>; Ian Jackson <Ian.Jackson@xxxxxxxxxx>; Konrad 
> Rzeszutek Wilk
> <konrad.wilk@xxxxxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>; Tim 
> (Xen.org) <tim@xxxxxxx>;
> Wei Liu <wl@xxxxxxx>; Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>; Roger 
> Pau Monne
> <roger.pau@xxxxxxxxxx>
> Subject: Re: [PATCH v8 5/6] iommu: tidy up iommu_use_hap_pt() and 
> need_iommu_pt_sync() macros
> 
> Hi Paul,
> 
> On 9/2/19 3:50 PM, Paul Durrant wrote:
> > Thes macros really ought to live in the common xen/iommu.h header rather
> > then being distributed amongst architecture specific iommu headers and
> > xen/sched.h. This patch moves them there.
> >
> > NOTE: Disabling 'sharept' in the command line iommu options should really
> >        be hard error on ARM (as opposed to just being ignored), so define
> >        'iommu_hap_pt_share' to be true for ARM then then gate parsing the
> >        command line option on '#ifndef iommu_hap_pt_share'.
> >
> > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> > Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> > ---
> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> > Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> > 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 <wl@xxxxxxx>
> > Cc: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
> > Cc: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
> >
> > Previously part of 
> > https://lists.xenproject.org/archives/html/xen-devel/2019-07/msg02267.html
> >
> > v7:
> >   - Re-work the ARM handling of 'sharept' as suggested by Jan
> >   - Make sure that need_iommu_pt_sync() always evaluates its argument
> > ---
> >   xen/drivers/passthrough/iommu.c |  8 +++++++-
> >   xen/include/asm-arm/iommu.h     |  3 ---
> >   xen/include/asm-x86/iommu.h     |  4 ----
> >   xen/include/xen/iommu.h         | 19 ++++++++++++++++++-
> >   xen/include/xen/sched.h         |  6 ------
> >   5 files changed, 25 insertions(+), 15 deletions(-)
> >
> > diff --git a/xen/drivers/passthrough/iommu.c 
> > b/xen/drivers/passthrough/iommu.c
> > index 4f71db95ea..aaf3b9fac0 100644
> > --- a/xen/drivers/passthrough/iommu.c
> > +++ b/xen/drivers/passthrough/iommu.c
> > @@ -49,7 +49,11 @@ int8_t __hwdom_initdata iommu_hwdom_reserved = -1;
> >    * default until we find a good solution to resolve it.
> >    */
> >   bool_t __read_mostly iommu_intpost;
> > -bool_t __read_mostly iommu_hap_pt_share = 1;
> > +
> > +#ifndef iommu_hap_pt_share
> > +bool __read_mostly iommu_hap_pt_share = true;
> > +#endif
> > +
> >   bool_t __read_mostly iommu_debug;
> >   bool_t __read_mostly amd_iommu_perdev_intremap = 1;
> >
> > @@ -102,8 +106,10 @@ static int __init parse_iommu_param(const char *s)
> >               iommu_hwdom_passthrough = val;
> >           else if ( (val = parse_boolean("dom0-strict", s, ss)) >= 0 )
> >               iommu_hwdom_strict = val;
> > +#ifndef iommu_hap_pt_share
> >           else if ( (val = parse_boolean("sharept", s, ss)) >= 0 )
> >               iommu_hap_pt_share = val;
> > +#endif
> >           else
> >               rc = -EINVAL;
> >
> > diff --git a/xen/include/asm-arm/iommu.h b/xen/include/asm-arm/iommu.h
> > index 1577e83d2b..77a94b29eb 100644
> > --- a/xen/include/asm-arm/iommu.h
> > +++ b/xen/include/asm-arm/iommu.h
> > @@ -20,9 +20,6 @@ struct arch_iommu
> >       void *priv;
> >   };
> >
> > -/* Always share P2M Table between the CPU and the IOMMU */
> > -#define iommu_use_hap_pt(d) is_iommu_enabled(d)
> > -
> >   const struct iommu_ops *iommu_get_ops(void);
> >   void iommu_set_ops(const struct iommu_ops *ops);
> >
> > diff --git a/xen/include/asm-x86/iommu.h b/xen/include/asm-x86/iommu.h
> > index 5071afd6a5..85741f7c96 100644
> > --- a/xen/include/asm-x86/iommu.h
> > +++ b/xen/include/asm-x86/iommu.h
> > @@ -86,10 +86,6 @@ struct iommu_init_ops {
> >
> >   extern const struct iommu_init_ops *iommu_init_ops;
> >
> > -/* Are we using the domain P2M table as its IOMMU pagetable? */
> > -#define iommu_use_hap_pt(d) \
> > -    (hap_enabled(d) && is_iommu_enabled(d) && iommu_hap_pt_share)
> > -
> >   void iommu_update_ire_from_apic(unsigned int apic, unsigned int reg, 
> > unsigned int value);
> >   unsigned int iommu_read_apic_from_ire(unsigned int apic, unsigned int 
> > reg);
> >   int iommu_setup_hpet_msi(struct msi_desc *);
> > diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
> > index 4b6871936c..87f9129b99 100644
> > --- a/xen/include/xen/iommu.h
> > +++ b/xen/include/xen/iommu.h
> > @@ -55,7 +55,13 @@ static inline bool_t dfn_eq(dfn_t x, dfn_t y)
> >   extern bool_t iommu_enable, iommu_enabled;
> >   extern bool_t force_iommu, iommu_verbose, iommu_igfx;
> >   extern bool_t iommu_snoop, iommu_qinval, iommu_intremap, iommu_intpost;
> > -extern bool_t iommu_hap_pt_share;
> > +
> > +#ifdef CONFIG_ARM
> > +#define iommu_hap_pt_share true
> > +#else
> > +extern bool iommu_hap_pt_share;
> > +#endif
> 
> I don't particularly like #ifdef CONFIG_<ARCH> in common header. How
> about other arch? I can see two solutions:
> 
> 1) Move the define in asm/iommu.h. This would require to move the
> declaration a bit later and then protect as you did in iommu.c
> 2) Replace CONFIG_ARM with a new Kconfig selected by Arm only so far.
> 

I had wondered about a Kconfig but I can't really think of a good name. How 
about CONFIG_FORCE_PT_SHARE?

  Paul

> Cheers,
> 
> --
> Julien Grall
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