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Message-ID: <20170214155436.GC23718@leverpostej>
Date: Tue, 14 Feb 2017 15:54:36 +0000
From: Mark Rutland <mark.rutland@....com>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC: <linux-arm-kernel@...ts.infradead.org>, <catalin.marinas@....com>,
<will.deacon@....com>, <labbott@...oraproject.org>,
<kvmarm@...ts.cs.columbia.edu>, <marc.zyngier@....com>,
<andre.przywara@....com>, <Suzuki.Poulose@....com>, <james.morse@....com>,
<keescook@...omium.org>, <kernel-hardening@...ts.openwall.com>, <nd@....com>
Subject: Re: [PATCH v2 2/5] arm64: mmu: move TLB maintenance from callers to
create_mapping_late()
On Sat, Feb 11, 2017 at 08:23:03PM +0000, Ard Biesheuvel wrote:
> In preparation of changing the way we invoke create_mapping_late() (which
> is currently invoked twice from the same function), move the TLB flushing
> it performs from the caller into create_mapping_late() itself, and change
> it to a TLB maintenance by VA rather than a full flush, which is more
> appropriate here.
It's not immediately clear what's meant by "changing the way we invoke
create_mapping_late()" here.
It's probably worth explicitly mentioning that we need to add another
caller of create_mapping_late(), and this saves us adding (overly
strong) TLB maintenance to all callers.
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> ---
> arch/arm64/mm/mmu.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 2131521ddc24..9e0ec1a8cd3b 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -356,6 +356,9 @@ static void create_mapping_late(phys_addr_t phys, unsigned long virt,
>
> __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot,
> NULL, debug_pagealloc_enabled());
> +
> + /* flush the TLBs after updating live kernel mappings */
> + flush_tlb_kernel_range(virt, virt + size);
> }
It feels a little odd to have the maintenance here given we still call
this *create*_mapping_late.
Given the only users of this are changing permissions, perhaps we should
rename this to change_mapping_prot(), or something like that?
Otherwise, this looks fine to me, and boots fine. Either way:
Reviewed-by: Mark Rutland <mark.rutland@....com>
Tested-by: Mark Rutland <mark.rutland@....com>
Thanks,
Mark.
> static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end)
> @@ -438,9 +441,6 @@ void mark_rodata_ro(void)
> create_mapping_late(__pa_symbol(__start_rodata), (unsigned long)__start_rodata,
> section_size, PAGE_KERNEL_RO);
>
> - /* flush the TLBs after updating live kernel mappings */
> - flush_tlb_all();
> -
> debug_checkwx();
> }
>
> --
> 2.7.4
>
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