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Subject: Re: [PATCH v12 04/10] set_memory: allow querying whether
 set_direct_map_*() is actually enabled
To:     Mike Rapoport <rppt@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Andy Lutomirski <luto@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
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        Christopher Lameter <cl@linux.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Elena Reshetova <elena.reshetova@intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        James Bottomley <jejb@linux.ibm.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Matthew Wilcox <willy@infradead.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Rick Edgecombe <rick.p.edgecombe@intel.com>,
        Roman Gushchin <guro@fb.com>, Shuah Khan <shuah@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tycho Andersen <tycho@tycho.ws>, Will Deacon <will@kernel.org>,
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        x86@kernel.org
References: <20201125092208.12544-1-rppt@kernel.org>
 <20201125092208.12544-5-rppt@kernel.org>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <5ea6eacd-79e8-0645-da39-d3461f60e627@redhat.com>
Date:   Wed, 25 Nov 2020 12:22:52 +0100
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>  #include <asm-generic/cacheflush.h>
>  
>  #endif /* __ASM_CACHEFLUSH_H */
> diff --git a/arch/arm64/include/asm/set_memory.h b/arch/arm64/include/asm/set_memory.h
> new file mode 100644
> index 000000000000..ecb6b0f449ab
> --- /dev/null
> +++ b/arch/arm64/include/asm/set_memory.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef _ASM_ARM64_SET_MEMORY_H
> +#define _ASM_ARM64_SET_MEMORY_H
> +
> +#include <asm-generic/set_memory.h>
> +
> +bool can_set_direct_map(void);
> +#define can_set_direct_map can_set_direct_map

Well, that looks weird.
[...]

>  }
> +#else /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */
> +/*
> + * Some architectures, e.g. ARM64 can disable direct map modifications at
> + * boot time. Let them overrive this query.
> + */
> +#ifndef can_set_direct_map
> +static inline bool can_set_direct_map(void)
> +{
> +	return true;
> +}

I think we prefer __weak functions for something like that, avoids the
ifdefery.

Apart from that, LGTM.

-- 
Thanks,

David / dhildenb