linux-kernel - Re: [PATCH v3 3/4] arch, mm: restore dependency of __kernel_map_pages() of DEBUG

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Date:   Mon, 2 Nov 2020 10:23:20 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Albert Ou <aou@...s.berkeley.edu>,
        Andy Lutomirski <luto@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Christoph Lameter <cl@...ux.com>,
        "David S. Miller" <davem@...emloft.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Len Brown <len.brown@...el.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Pavel Machek <pavel@....cz>, Pekka Enberg <penberg@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-pm@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org,
        x86@...nel.org
Subject: Re: [PATCH v3 3/4] arch, mm: restore dependency of
 __kernel_map_pages() of DEBUG_PAGEALLOC


>   int __init kernel_map_pages_in_pgd(pgd_t *pgd, u64 pfn, unsigned long address,
>   				   unsigned numpages, unsigned long page_flags)
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 14e397f3752c..ab0ef6bd351d 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2924,7 +2924,11 @@ static inline bool debug_pagealloc_enabled_static(void)
>   	return static_branch_unlikely(&_debug_pagealloc_enabled);
>   }
>   
> -#if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_ARCH_HAS_SET_DIRECT_MAP)
> +#ifdef CONFIG_DEBUG_PAGEALLOC
> +/*
> + * To support DEBUG_PAGEALLOC architecture must ensure that
> + * __kernel_map_pages() never fails

Maybe add here, that this implies mapping everything via PTEs during boot.

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb