linux-kernel - Re: [v2 3/5] arm64: mte: implement CONFIG_ARM64_MTE

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Date:   Thu, 13 Jul 2023 18:37:43 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     glider@...gle.com, catalin.marinas@....com, will@...nel.org,
        pcc@...gle.com, andreyknvl@...il.com,
        andriy.shevchenko@...ux.intel.com, linux@...musvillemoes.dk,
        yury.norov@...il.com
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        eugenis@...gle.com
Subject: Re: [v2 3/5] arm64: mte: implement CONFIG_ARM64_MTE_COMP

> +/* Compress the data inline. */
> +static u64 ea0_compress_inline(int len, u8 *tags, short *sizes)
> +{
> +       u64 result;
> +
> +       ea0_compress_to_buf(len, tags, sizes, (u8 *)&result, sizeof(result));
> +       result = be64_to_cpu(result);
This be64_to_cpu() is leftover from the previous compressor
implementation which treated u64 as u8[8] (i.e. big-endian).
The new implementation works with the native u64 representation, so
the conversion is not needed anymore (and actually produces invalid
handles that can't be stored in Xarray).
I will drop this call in v3.


> +bool ea0_decompress(u64 handle, u8 *tags)
> +{
> +       u8 *storage = ea0_storage(handle);
> +       int size = ea0_storage_size(handle);
> +
> +       if (size == 128) {
> +               memcpy(tags, storage, size);
> +               return true;
> +       }
> +       if (size == 8) {
> +               handle = cpu_to_be64(handle);
Ditto.