Re: [PATCH v3] xen: introduce XENFEAT_direct_mapped and XENFEAT_not_direct_mapped

[Julien Grall <julien@xxxxxxx>]

Hi Stefano,

On 17/03/2021 00:04, Stefano Stabellini wrote:
> On Tue, 16 Mar 2021, Jan Beulich wrote:
> > On 15.03.2021 21:01, Stefano Stabellini wrote:
> > > On Mon, 15 Mar 2021, Jan Beulich wrote:
> > > > On 13.03.2021 00:16, Stefano Stabellini wrote:
> > > > > Introduce two feature flags to tell the domain whether it is
> > > > > direct-mapped or not. It allows the guest kernel to make informed
> > > > > decisions on things such as swiotlb-xen enablement.
> > > > >
> > > > > The introduction of both flags (XENFEAT_direct_mapped and
> > > > > XENFEAT_not_direct_mapped) allows the guest kernel to avoid any
> > > > > guesswork if one of the two is present, or fallback to the current
> > > > > checks if neither of them is present.
> > > > >
> > > > > XENFEAT_direct_mapped is always set for not auto-translated guests.
> > > > >
> > > > > For auto-translated guests, only Dom0 on ARM is direct-mapped. Also,
> > > > > see is_domain_direct_mapped() which refers to auto-translated guests:
> > > > > xen/include/asm-arm/domain.h:is_domain_direct_mapped
> > > > > xen/include/asm-x86/domain.h:is_domain_direct_mapped
> > > > >
> > > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> > > > > CC: jbeulich@xxxxxxxx
> > > > > CC: andrew.cooper3@xxxxxxxxxx
> > > > > CC: julien@xxxxxxx
> > > > Any particular reason my previously given R-b isn't here?
> > > I reworded part of the comment in the public header, and I decided to
> > > err on the side of caution and not add your R-b given this change
> > > compared to the previous version.
> > I see. FAOD, despite me not being overly happy with the "older
> > Xen assumptions" part of the comment, feel free to add it back.
> Thank you!
>
> Julien, please go ahead and commit it to your for-next/4.16 branch when
> it is convenient.
I have committed it to my for-next/4.16 branch. I will merge the branch 
after the tree has re-opened.
Cheers,

--
Julien Grall