linux-kernel - Re: [PATCH 1/3] csky: Fixup arch_get_unmapped

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Message-ID: <20190821021650.GA32710@infradead.org>
Date:   Tue, 20 Aug 2019 19:16:50 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     guoren@...nel.org
Cc:     arnd@...db.de, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-csky@...r.kernel.org,
        douzhk@...ionalchip.com, Guo Ren <ren_guo@...ky.com>
Subject: Re: [PATCH 1/3] csky: Fixup arch_get_unmapped_area() implementation

> +/*
> + * We need to ensure that shared mappings are correctly aligned to
> + * avoid aliasing issues with VIPT caches.  We need to ensure that
> + * a specific page of an object is always mapped at a multiple of
> + * SHMLBA bytes.
> + *
> + * We unconditionally provide this function for all cases.
> + */

On something unrelated: If csky has virtually indexed caches you also
need to implement the flush_kernel_vmap_range and
invalidate_kernel_vmap_range functions to avoid data corruption when
doing I/O on vmalloc/vmap ranges.