Re: [PATCH v7] xen/domain: rewrite emulation_flags_ok()

["Roger Pau Monné" <roger.pau@citrix.com>]

On Mon, Jun 16, 2025 at 04:03:14PM +0200, Roger Pau Monné wrote:
> On Tue, Jun 10, 2025 at 02:45:12PM +0000, dmkhn@proton.me wrote:
> > From: Denis Mukhin <dmukhin@ford.com>
> > 
> > Rewrite emulation_flags_ok() to simplify future modifications.
> > 
> > No functional change intended.
> > 
> > Signed-off-by: Denis Mukhin <dmukhin@ford.com>
> > ---
> > Changes since v6:
> > - simplified checks for PV further
> > 
> > Link to v6: https://lore.kernel.org/xen-devel/20250610004216.3012253-1-dmukhin@ford.com/
> > Link to CI: https://gitlab.com/xen-project/people/dmukhin/xen/-/pipelines/1862559089
> > ---
> >  xen/arch/x86/domain.c | 78 +++++++++++++++++++++++++++++++++----------
> >  1 file changed, 60 insertions(+), 18 deletions(-)
> > 
> > diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> > index 7536b6c871..fdbd064ebf 100644
> > --- a/xen/arch/x86/domain.c
> > +++ b/xen/arch/x86/domain.c
> > @@ -743,32 +743,74 @@ int arch_sanitise_domain_config(struct xen_domctl_createdomain *config)
> >      return 0;
> >  }
> >  
> > +/*
> > + * Verify that the domain's emulation flags resolve to a supported configuration.
> > + *
> > + * This ensures we only allow a known, safe subset of emulation combinations
> > + * (for both functionality and security). Arbitrary mixes are likely to cause
> > + * errors (e.g. null pointer dereferences).
> > + *
> > + * NB: use the internal X86_EMU_XXX symbols, not the public XEN_X86_EMU_XXX
> > + * symbols.
> 
> Not sure if it's worth expanding the sentence a bit to add the reason
> why X86_EMU_XXX should be used (so that we take build-time config
> options into account for short-circuited emulations).

With this comment adjusted as you have in v8:

Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.