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Date:   Wed, 25 Nov 2020 18:36:45 +0000
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Mike Rapoport <rppt@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andy Lutomirski <luto@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Christopher Lameter <cl@linux.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        David Hildenbrand <david@redhat.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>,
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Subject: Re: [PATCH v12 04/10] set_memory: allow querying whether
 set_direct_map_*() is actually enabled
Message-ID: <20201125183645.GB16801@gaia>
References: <20201125092208.12544-1-rppt@kernel.org>
 <20201125092208.12544-5-rppt@kernel.org>
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On Wed, Nov 25, 2020 at 11:22:02AM +0200, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@linux.ibm.com>
> 
> On arm64, set_direct_map_*() functions may return 0 without actually
> changing the linear map. This behaviour can be controlled using kernel
> parameters, so we need a way to determine at runtime whether calls to
> set_direct_map_invalid_noflush() and set_direct_map_default_noflush() have
> any effect.
> 
> Extend set_memory API with can_set_direct_map() function that allows
> checking if calling set_direct_map_*() will actually change the page table,
> replace several occurrences of open coded checks in arm64 with the new
> function and provide a generic stub for architectures that always modify
> page tables upon calls to set_direct_map APIs.
> 
> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>