Re: [Minios-devel] [PATCH v3 19/43] arm64: add shared_info support

[Julien Grall <julien.grall@xxxxxxx>]

On 04/25/2018 06:48 AM, Huang Shijie wrote:
> On Mon, Apr 23, 2018 at 12:05:51PM +0100, Julien Grall wrote:
> > Hi Shijie,
> >
> > On 23/04/18 09:49, Huang Shijie wrote:
> > > On Wed, Apr 18, 2018 at 09:34:18PM +0100, Julien Grall wrote:
> > > > Hi,
> > > >
> > > > On 16/04/2018 07:31, Huang Shijie wrote:
> > > > > Add the shared_info page.
> > > > >
> > > > > Signed-off-by: Huang Shijie <shijie.huang@xxxxxxx>
> > > > > ---
> > > > >   arch/arm/arm64/arm64.S | 3 +++
> > > > >   1 file changed, 3 insertions(+)
> > > > >
> > > > > diff --git a/arch/arm/arm64/arm64.S b/arch/arm/arm64/arm64.S
> > > > > index 9eb7ea0..fa3406f 100644
> > > > > --- a/arch/arm/arm64/arm64.S
> > > > > +++ b/arch/arm/arm64/arm64.S
> > > > > @@ -25,6 +25,7 @@
> > > > >       .globl boot_l2_pgtable
> > > > >       .globl idmap_l0_pgtable
> > > > >       .globl idmap_l1_pgtable
> > > > > +    .globl shared_info
> > > > >       .align 12
> > > > >   boot_l0_pgtable:
> > > > > @@ -37,6 +38,8 @@ idmap_l0_pgtable:
> > > > >       .fill  PAGE_SIZE,1,0
> > > > >   idmap_l1_pgtable:
> > > > >       .fill  PAGE_SIZE,1,0
> > > > > +shared_info:
> > > > > +    .fill  PAGE_SIZE,1,0
> > > > Why does it have to be defined in assembly? Can't this be done in C? Or even
> > > I think we'd better keep it here.
> > Assembly should really only be used when this is strictly necessary...
> >
> > > We used the shared_info at arch_init() which the memory system is not ready yet.
> > ... if it is used in arch_init() then it should be defined in C statically.
> I found it is hard to code it in C.
>
> The following is what I did:
>
>    ----------------------------------------------------------
>    shared_info_t shared_info __attribute__((aligned(PAGE_SIZE)));
>    ----------------------------------------------------------
>
> But we need the shared_info to occupy a whole page which is
> used in map_shared_info().
>
> Is there a good way to solve it?
char shared_info[PAGE_SIZE] __attribute__((aligned(PAGE_SIZE));

Cheers,

--
Julien Grall

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