Re: [PATCH v7 3/4] arm64: Make use of memblock_isolate_memory for the linear mapping

[Alexandre Ghiti]

Hi Andrew,

On 3/13/23 10:43, Andrew Jones wrote:
> On Fri, Mar 10, 2023 at 10:45:38AM +0100, Alexandre Ghiti wrote:
> > In order to isolate the kernel text mapping, we used some sort of hack
> > to isolate the kernel text range which consisted in marking this region
> > as not mappable with memblock_mark_nomap. Simply use the newly introduced
> > memblock_isolate_memory function which does exactly the same but does not
> > uselessly mark the region as not mappable.
> >
> > Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
> > ---
> >   arch/arm64/mm/mmu.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index 6f9d8898a025..408dc852805c 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -552,7 +552,7 @@ static void __init map_mem(pgd_t *pgdp)
> >   	 * So temporarily mark them as NOMAP to skip mappings in
> >   	 * the following for-loop
> >   	 */
> The comment above doesn't apply anymore.


Yep, noticed this one after sending, thanks anyway!


> > -	memblock_mark_nomap(kernel_start, kernel_end - kernel_start);
> > +	memblock_isolate_memory(kernel_start, kernel_end - kernel_start);
> >   
> >   #ifdef CONFIG_KEXEC_CORE
> >   	if (crash_mem_map) {
> > @@ -568,6 +568,7 @@ static void __init map_mem(pgd_t *pgdp)
> >   	for_each_mem_range(i, &start, &end) {
> >   		if (start >= end)
> >   			break;
> > +
> Mark nomap is also used for the crash kernel. Does the new API not work
> for it?


Seems you're right, I missed it.

Thanks,

Alex


> Thanks,
> drew
>
> >   		/*
> >   		 * The linear map must allow allocation tags reading/writing
> >   		 * if MTE is present. Otherwise, it has the same attributes as
> > @@ -589,7 +590,6 @@ static void __init map_mem(pgd_t *pgdp)
> >   	 */
> >   	__map_memblock(pgdp, kernel_start, kernel_end,
> >   		       PAGE_KERNEL, NO_CONT_MAPPINGS);
> > -	memblock_clear_nomap(kernel_start, kernel_end - kernel_start);
> >   
> >   	/*
> >   	 * Use page-level mappings here so that we can shrink the region
> > --
> > 2.37.2
> >
> >
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