[linux-next PATCH] arm64: fix kernel crash with 48-bit VA and 64KB granule
dennis.chen at arm.com
Tue Jan 5 00:40:44 PST 2016
On Tue, Jan 05, 2016 at 09:38:11AM +0100, Ard Biesheuvel wrote:
> On 5 January 2016 at 09:35, Dennis Chen <dennis.chen at arm.com> wrote:
> > On Tue, Jan 05, 2016 at 08:36:39AM +0100, Ard Biesheuvel wrote:
> >> On 5 January 2016 at 03:18, Dennis Chen <dennis.chen at arm.com> wrote:
> >> > The commit 3400749b5a22 ("arm64/efi: refactor EFI init and runtime
> >> > code for reuse by 32-bit ARM") uses pgd_alloc() to allocate space for
> >> > efi_mm.pgd while not the static efi_pgd, since this function will be
> >> > called with early_initcall, which results in the pgd_cache used by
> >> > pgd_alloc() has not been initialized yet, kernel will hang in this
> >> > case. This patch is trying to make the pgd_cache_init() called before
> >> > arm_enable_runtime_services() by changing its core_initcall to
> >> > early_initcall.
> >> >
> >> > Signed-off-by: Dennis Chen <dennis.chen at arm.com>
> >> > Tested-by: Sudeep Holla <sudeep.holla at arm.com>
> >> >
> >> > Cc: Will Deacon <will.deacon at arm.com>
> >> > Cc: Catalin Marinas <catalin.marinas at arm.com>
> >> > Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> >> > Cc: Sudeep Holla <sudeep.holla at arm.com>
> >> > ---
> >> > arch/arm64/mm/pgd.c | 2 +-
> >> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >> >
> >> > diff --git a/arch/arm64/mm/pgd.c b/arch/arm64/mm/pgd.c
> >> > index cb3ba1b..859a788 100644
> >> > --- a/arch/arm64/mm/pgd.c
> >> > +++ b/arch/arm64/mm/pgd.c
> >> > @@ -56,4 +56,4 @@ static int __init pgd_cache_init(void)
> >> > SLAB_PANIC, NULL);
> >> > return 0;
> >> > }
> >> > -core_initcall(pgd_cache_init);
> >> > +early_initcall(pgd_cache_init);
> >> Hello all,
> >> Apologies for not spotting this before sending it out.
> >> The issue only occurs when PGD_SIZE != PAGE_SIZE, which is why I did
> >> not see it myself. I only tested with 4k/39-bits and 64k/42-bits IIRC,
> >> since the series this is part of primarily concerns ARM not arm64.
> >> Anyway, shuffling init ordering is my least favorite way of fixing
> >> bugs. Since only ARM requires pgd_alloc() (for the kernel mappings),
> >> we could also simply factor out pgd_alloc() into efi_pgd_alloc(), and
> >> define it to mean '__get_free_page(PGALLOC_GFP)' on arm64.
> > Ard,
> > Both arm and arm64 provide pgd_alloc(), I don't think it's a good idea to create
> > another efi_pgd_alloc() used by efi only, which looks more like a temp workaround.
> > Plus, for 64KB page granule when VA = 48bit, the PGD_SIZE = 0x200, it doesn't make
> > sense to get an entire page as the space for the efi.pgd. Changing the init order
> > sequence is a reasonable way to fix it unless you can see some potential issues there.
> Well, since arm_enable_runtime_services() is an early_initcall()
> itself, how are you guaranteeing the ordering between the two? Link
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