From mboxrd@z Thu Jan 1 00:00:00 1970 From: ard.biesheuvel@linaro.org (Ard Biesheuvel) Date: Tue, 5 Jan 2016 09:38:11 +0100 Subject: [linux-next PATCH] arm64: fix kernel crash with 48-bit VA and 64KB granule In-Reply-To: <20160105083533.GD13942@arm.org> References: <1451960299-14123-1-git-send-email-dennis.chen@arm.com> <20160105083533.GD13942@arm.org> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 5 January 2016 at 09:35, Dennis Chen wrote: > On Tue, Jan 05, 2016 at 08:36:39AM +0100, Ard Biesheuvel wrote: >> On 5 January 2016 at 03:18, Dennis Chen 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 >> > Tested-by: Sudeep Holla >> > >> > Cc: Will Deacon >> > Cc: Catalin Marinas >> > Cc: Ard Biesheuvel >> > Cc: Sudeep Holla >> > --- >> > 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 order?