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

[Zhang Chen]

Hi,Dave


On 12/01/2015 07:23 PM, Dr. David Alan Gilbert wrote:
> * 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

I will remove it and change it to kernel jhash.h's copyright in next version

Thanks for review
zhangchen

> > +
> > +#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
>
>
> .