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

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Message-ID: <259cac45-3337-d446-5abc-21b694d916e1@oracle.com>
Date:   Fri, 15 Feb 2019 07:47:37 -0700
From:   Khalid Aziz <khalid.aziz@...cle.com>
To:     Mark Rutland <mark.rutland@....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,
        joao.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

On 2/15/19 6:09 AM, Mark Rutland wrote:
> 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.

That sounds reasonable to me. I will merge this with patch 5 ("arm64/mm:
Add support for XPFO") for the next version unless there are objections.

Thanks,
Khalid

> 
>> ---
>>  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
>>