Re: [PATCH 08/12] xen/arm: if is_domain_direct_mapped use native addresses for GICv2

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 15 Apr 2020, Julien Grall wrote:
> On 15/04/2020 02:02, Stefano Stabellini wrote:
> > Today we use native addresses to map the GICv2 for Dom0 and fixed
> > addresses for DomUs.
> > 
> > This patch changes the behavior so that native addresses are used for
> > any domain that is_domain_direct_mapped.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> > ---
> >   xen/arch/arm/domain_build.c | 10 +++++++---
> >   xen/arch/arm/vgic-v2.c      | 12 ++++++------
> >   xen/arch/arm/vgic/vgic-v2.c |  2 +-
> >   xen/include/asm-arm/vgic.h  |  1 +
> >   4 files changed, 15 insertions(+), 10 deletions(-)
> > 
> > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> > index 627e0c5e8e..303bee60f6 100644
> > --- a/xen/arch/arm/domain_build.c
> > +++ b/xen/arch/arm/domain_build.c
> > @@ -1643,8 +1643,12 @@ static int __init make_gicv2_domU_node(struct
> > kernel_info *kinfo)
> >       int res = 0;
> >       __be32 reg[(GUEST_ROOT_ADDRESS_CELLS + GUEST_ROOT_SIZE_CELLS) * 2];
> >       __be32 *cells;
> > +    struct domain *d = kinfo->d;
> > +    char buf[38];
> >   -    res = fdt_begin_node(fdt,
> > "interrupt-controller@"__stringify(GUEST_GICD_BASE));
> > +    snprintf(buf, sizeof(buf), "interrupt-controller@%"PRIx64,
> > +             d->arch.vgic.dbase);
> > +    res = fdt_begin_node(fdt, buf);
> >       if ( res )
> >           return res;
> >   @@ -1666,9 +1670,9 @@ static int __init make_gicv2_domU_node(struct
> > kernel_info *kinfo)
> >         cells = &reg[0];
> >       dt_child_set_range(&cells, GUEST_ROOT_ADDRESS_CELLS,
> > GUEST_ROOT_SIZE_CELLS,
> > -                       GUEST_GICD_BASE, GUEST_GICD_SIZE);
> > +                       d->arch.vgic.dbase, GUEST_GICD_SIZE);
> >       dt_child_set_range(&cells, GUEST_ROOT_ADDRESS_CELLS,
> > GUEST_ROOT_SIZE_CELLS,
> > -                       GUEST_GICC_BASE, GUEST_GICC_SIZE);
> > +                       d->arch.vgic.cbase, GUEST_GICC_SIZE);
> 
> You can't use the native base address and not the native size. Particularly,
> this is going to screw any GIC using 8KB alias.

I don't follow why it could cause problems with a GIC using the 8KB
alias. Maybe an example (even a fake example) would help.



> It would be preferable if only expose part of the CPU interface as we do for
> the guest. So d->arch.vgic.cbase would be equal to vgic_v2_hw.dbase +
> vgic_v2.hw.aliased_offset.