linux-kernel - Re: [RFC PATCH v8 08/14] arm64/mm: disable section/contiguous mappings if XPFO is enabled

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Message-ID: <20190215130942.GD53520@lakrids.cambridge.arm.com>
Date:   Fri, 15 Feb 2019 13:09:42 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Khalid Aziz <khalid.aziz@...cle.com>
Cc:     juergh@...il.com, tycho@...ho.ws, jsteckli@...zon.de,
        ak@...ux.intel.com, torvalds@...ux-foundation.org,
        liran.alon@...cle.com, keescook@...gle.com,
        akpm@...ux-foundation.org, mhocko@...e.com,
        catalin.marinas@....com, will.deacon@....com, jmorris@...ei.org,
        konrad.wilk@...cle.com, Tycho Andersen <tycho@...ker.com>,
        deepa.srinivasan@...cle.com, chris.hyser@...cle.com,
        tyhicks@...onical.com, dwmw@...zon.co.uk,
        andrew.cooper3@...rix.com, jcm@...hat.com,
        boris.ostrovsky@...cle.com, kanth.ghatraju@...cle.com,
        oao.m.martins@...cle.com, jmattson@...gle.com,
        pradeep.vincent@...cle.com, john.haxby@...cle.com,
        tglx@...utronix.de, kirill.shutemov@...ux.intel.com, hch@....de,
        steven.sistare@...cle.com, labbott@...hat.com, luto@...nel.org,
        dave.hansen@...el.com, peterz@...radead.org,
        kernel-hardening@...ts.openwall.com, linux-mm@...ck.org,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v8 08/14] arm64/mm: disable section/contiguous
 mappings if XPFO is enabled

Hi,

On Wed, Feb 13, 2019 at 05:01:31PM -0700, Khalid Aziz wrote:
> From: Tycho Andersen <tycho@...ker.com>
> 
> XPFO doesn't support section/contiguous mappings yet, so let's disable it
> if XPFO is turned on.
> 
> Thanks to Laura Abbot for the simplification from v5, and Mark Rutland for
> pointing out we need NO_CONT_MAPPINGS too.
> 
> CC: linux-arm-kernel@...ts.infradead.org
> Signed-off-by: Tycho Andersen <tycho@...ker.com>
> Reviewed-by: Khalid Aziz <khalid.aziz@...cle.com>

There should be no point in this series where it's possible to enable a
broken XPFO. Either this patch should be merged into the rest of the
arm64 bits, or it should be placed before the rest of the arm64 bits.

That's a pre-requisite for merging, and it significantly reduces the
burden on reviewers.

In general, a patch series should bisect cleanly. Could you please
restructure the series to that effect?

Thanks,
Mark.

> ---
>  arch/arm64/mm/mmu.c  | 2 +-
>  include/linux/xpfo.h | 4 ++++
>  mm/xpfo.c            | 6 ++++++
>  3 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index d1d6601b385d..f4dd27073006 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -451,7 +451,7 @@ static void __init map_mem(pgd_t *pgdp)
>  	struct memblock_region *reg;
>  	int flags = 0;
>  
> -	if (debug_pagealloc_enabled())
> +	if (debug_pagealloc_enabled() || xpfo_enabled())
>  		flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>  
>  	/*
> diff --git a/include/linux/xpfo.h b/include/linux/xpfo.h
> index 1ae05756344d..8b029918a958 100644
> --- a/include/linux/xpfo.h
> +++ b/include/linux/xpfo.h
> @@ -47,6 +47,8 @@ void xpfo_temp_map(const void *addr, size_t size, void **mapping,
>  void xpfo_temp_unmap(const void *addr, size_t size, void **mapping,
>  		     size_t mapping_len);
>  
> +bool xpfo_enabled(void);
> +
>  #else /* !CONFIG_XPFO */
>  
>  static inline void xpfo_kmap(void *kaddr, struct page *page) { }
> @@ -69,6 +71,8 @@ static inline void xpfo_temp_unmap(const void *addr, size_t size,
>  }
>  
>  
> +static inline bool xpfo_enabled(void) { return false; }
> +
>  #endif /* CONFIG_XPFO */
>  
>  #endif /* _LINUX_XPFO_H */
> diff --git a/mm/xpfo.c b/mm/xpfo.c
> index 92ca6d1baf06..150784ae0f08 100644
> --- a/mm/xpfo.c
> +++ b/mm/xpfo.c
> @@ -71,6 +71,12 @@ struct page_ext_operations page_xpfo_ops = {
>  	.init = init_xpfo,
>  };
>  
> +bool __init xpfo_enabled(void)
> +{
> +	return !xpfo_disabled;
> +}
> +EXPORT_SYMBOL(xpfo_enabled);
> +
>  static inline struct xpfo *lookup_xpfo(struct page *page)
>  {
>  	struct page_ext *page_ext = lookup_page_ext(page);
> -- 
> 2.17.1
>