Re: [PATCH v5 1/5] xen/arm32: head: Widen the use of the temporary mapping

[Julien Grall <julien@xxxxxxx>]

On 30/01/2023 08:58, Michal Orzel wrote:
> Hi Julien,
Hi Michal,

> On 27/01/2023 20:55, Julien Grall wrote:
> > From: Julien Grall <jgrall@xxxxxxxxxx>
> >
> > At the moment, the temporary mapping is only used when the virtual
> > runtime region of Xen is clashing with the physical region.
> >
> > In follow-up patches, we will rework how secondary CPU bring-up works
> > and it will be convenient to use the fixmap area for accessing
> > the root page-table (it is per-cpu).
> >
> > Rework the code to use temporary mapping when the Xen physical address
> > is not overlapping with the temporary mapping.
> >
> > This also has the advantage to simplify the logic to identity map
> > Xen.
> >
> > Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
> >
> > ---
> >
> > Even if this patch is rewriting part of the previous patch, I decided
> > to keep them separated to help the review.
> >
> > The "follow-up patches" are still in draft at the moment. I still haven't
> > find a way to split them nicely and not require too much more work
> > in the coloring side.
> >
> > I have provided some medium-term goal in the cover letter.
> >
> >      Changes in v5:
> >          - Fix typo in a comment
> >          - No need to link boot_{second, third}_id again if we need to
> >            create a temporary area.
> >
> >      Changes in v3:
> >          - Resolve conflicts after switching from "ldr rX, <label>" to
> >            "mov_w rX, <label>" in a previous patch
> >
> >      Changes in v2:
> >          - Patch added
> > ---
> >   xen/arch/arm/arm32/head.S | 85 +++++++--------------------------------
> >   1 file changed, 15 insertions(+), 70 deletions(-)
> >
> > diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> > index df51550baa8a..93b0af114b0c 100644
> > --- a/xen/arch/arm/arm32/head.S
> > +++ b/xen/arch/arm/arm32/head.S
> ...
> > @@ -675,33 +641,12 @@ remove_identity_mapping:
> >           /* r2:r3 := invalid page-table entry */
> >           mov   r2, #0x0
> >           mov   r3, #0x0
> > -        /*
> > -         * Find the first slot used. Remove the entry for the first
> > -         * table if the slot is not XEN_FIRST_SLOT.
> > -         */
> Could you please add an empty line here to improve readability?
Sure. I will do that on commit.

> > +        /* Find the first slot used and remove it */
> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
Thanks!

Cheers,

--
Julien Grall