Re: [Qemu-devel] [RFC PATCH 2/9] jhash: add linux kernel jhashtable in qemu

[Dr. David Alan Gilbert]

* Zhang Chen (address@hidden) wrote:
> From: zhangchen <address@hidden>
> 
> This used by colo-proxy to save and lookup
> connection info
> 
> Signed-off-by: zhangchen <address@hidden>
> ---
>  include/qemu/jhash.h | 52 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
>  create mode 100644 include/qemu/jhash.h
> 
> diff --git a/include/qemu/jhash.h b/include/qemu/jhash.h
> new file mode 100644
> index 0000000..f6cc7b3
> --- /dev/null
> +++ b/include/qemu/jhash.h
> @@ -0,0 +1,52 @@
> +/*
> + * COarse-grain LOck-stepping Virtual Machines for Non-stop Service (COLO)
> + * (a.k.a. Fault Tolerance or Continuous Replication)
> + *
> + * Copyright (c) 2015 HUAWEI TECHNOLOGIES CO., LTD.
> + * Copyright (c) 2015 FUJITSU LIMITED
> + * Copyright (c) 2015 Intel Corporation
> + *
> + * Author: Zhang Chen <address@hidden>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * later.  See the COPYING file in the top-level directory.
> + */

Please be careful with the copyright.
This code is mostly a copy of the kernel code, so I think it should take the 
copyright
from the kernel code (see kernel's include/linux/jhash.h); and that copyright
states it's based on Bob Jenkins' Public Domain code.
Normally we have a problem as well QEMU doesn't like taking GPL2 code from the 
kernel,
but my reading of the kernel's header file is that it's still Public domain; 
but I don't
know what the right thing is to be sure.

Dave

> +
> +#ifndef QEMU_JHASH_H__
> +#define QEMU_JHASH_H__
> +
> +/*
> + * hashtable relation copy from linux kernel jhash
> + */
> +static inline uint32_t rol32(uint32_t word, unsigned int shift)
> +{
> +    return (word << shift) | (word >> (32 - shift));
> +}
> +
> +/* __jhash_mix -- mix 3 32-bit values reversibly. */
> +#define __jhash_mix(a, b, c)                \
> +{                                           \
> +    a -= c;  a ^= rol32(c, 4);  c += b;     \
> +    b -= a;  b ^= rol32(a, 6);  a += c;     \
> +    c -= b;  c ^= rol32(b, 8);  b += a;     \
> +    a -= c;  a ^= rol32(c, 16); c += b;     \
> +    b -= a;  b ^= rol32(a, 19); a += c;     \
> +    c -= b;  c ^= rol32(b, 4);  b += a;     \
> +}
> +
> +/* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
> +#define __jhash_final(a, b, c)  \
> +{                               \
> +    c ^= b; c -= rol32(b, 14);  \
> +    a ^= c; a -= rol32(c, 11);  \
> +    b ^= a; b -= rol32(a, 25);  \
> +    c ^= b; c -= rol32(b, 16);  \
> +    a ^= c; a -= rol32(c, 4);   \
> +    b ^= a; b -= rol32(a, 14);  \
> +    c ^= b; c -= rol32(b, 24);  \
> +}
> +
> +/* An arbitrary initial parameter */
> +#define JHASH_INITVAL           0xdeadbeef
> +
> +#endif /* QEMU_JHASH_H__ */
> -- 
> 1.9.1
> 
> 
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK