Re: [PATCH v1 5/6] xen: move domain_use_host_layout() to common header

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 16 Feb 2026, Jan Beulich wrote:
> On 12.02.2026 17:21, Oleksii Kurochko wrote:
> > domain_use_host_layout() is generic enough to be moved to the
> > common header xen/domain.h.
> 
> Maybe, but then something DT-specific, not xen/domain.h. Specifically, ...
> 
> > --- a/xen/include/xen/domain.h
> > +++ b/xen/include/xen/domain.h
> > @@ -62,6 +62,22 @@ void domid_free(domid_t domid);
> >  #define is_domain_direct_mapped(d) ((d)->cdf & CDF_directmap)
> >  #define is_domain_using_staticmem(d) ((d)->cdf & CDF_staticmem)
> >  
> > +/*
> > + * Is the domain using the host memory layout?
> > + *
> > + * Direct-mapped domain will always have the RAM mapped with GFN == MFN.
> > + * To avoid any trouble finding space, it is easier to force using the
> > + * host memory layout.
> > + *
> > + * The hardware domain will use the host layout regardless of
> > + * direct-mapped because some OS may rely on a specific address ranges
> > + * for the devices.
> > + */
> > +#ifndef domain_use_host_layout
> > +# define domain_use_host_layout(d) (is_domain_direct_mapped(d) || \
> > +                                    is_hardware_domain(d))
> 
> ... is_domain_direct_mapped() isn't something that I'd like to see further
> proliferate in common (non-DT) code.

Hi Jan, we have a requirement for 1:1 mapped Dom0 (I should say hardware
domain) on x86 as well. In fact, we already have a working prototype,
although it is not suitable for upstream yet.

In addition to the PSP use case that we discussed a few months ago,
where the PSP is not behind an IOMMU and therefore exchanged addresses
must be 1:1 mapped, we also have a new use case. We are running the full
Xen-based automotive stack on an Azure instance where SVM (vmentry and
vmexit) is available, but an IOMMU is not present. All virtual machines
are configured as PVH.