Re: [PATCH] riscv: Start of DRAM should at least be aligned on PMD size for the direct mapping

[Song Shuai]

在 2023/7/4 21:16, Alexandre Ghiti 写道:
> On Tue, Jul 4, 2023 at 2:26 PM Conor Dooley <conor.dooley@xxxxxxxxxxxxx> wrote:
> > Hey Alex,
> >
> > On Tue, Jul 04, 2023 at 02:18:37PM +0200, Alexandre Ghiti wrote:
> > > So that we do not end up mapping the whole linear mapping using 4K
> > > pages, which is slow at boot time, and also very likely at runtime.
> > >
> > > So make sure we align the start of DRAM on a PMD boundary.
> > >
> > > Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
> >
> > Obviously correct me if I am wrong here, but was this not reported by
> > Song Shuai as a regression?
> > Accordingly, should this not have Reported-by, Closes/Link & Fixes tags?
>
> Sure we should add the reported by from Song as he did the proper report :)
>
> Reported-by: Song Shuai <suagrfillet@xxxxxxxxx>
> Closes: https://lore.kernel.org/linux-riscv/20230625140931.1266216-1-songshuaishuai@xxxxxxxxxxx/
>
> And yes sorry, I thought it was there before, but it was actually when
> I retrieved the first 2MB that the problem appeared, so:
>
> Fixes: 3335068f8721 ("riscv: Use PUD/P4D/PGD pages for the linear mapping")
>
> Thanks!
And you can add my tested-by:

Tested-by: Song Shuai <suagrfillet@xxxxxxxxx>
> > Cheers,
> > Conor.
> >
> > > ---
> > >   arch/riscv/mm/init.c | 7 ++++++-
> > >   1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > > index 4fa420faa780..4a43ec275c6d 100644
> > > --- a/arch/riscv/mm/init.c
> > > +++ b/arch/riscv/mm/init.c
> > > @@ -214,8 +214,13 @@ static void __init setup_bootmem(void)
> > >        memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
> > >
> > >        phys_ram_end = memblock_end_of_DRAM();
> > > +
> > > +     /*
> > > +      * Make sure we align the start of the memory on a PMD boundary so that
> > > +      * at worst, we map the linear mapping with PMD mappings.
> > > +      */
> > >        if (!IS_ENABLED(CONFIG_XIP_KERNEL))
> > > -             phys_ram_base = memblock_start_of_DRAM();
> > > +             phys_ram_base = memblock_start_of_DRAM() & PMD_MASK;
> > >
> > >        /*
> > >         * In 64-bit, any use of __va/__pa before this point is wrong as we
> > > --
> > > 2.39.2

--
Thanks
Song Shuai