Re: [win-pv-devel] Xenbus hashtable usage

[RafaÅ WojdyÅa <omeg@xxxxxxxxxxxxxxxxxxxxxx>]

On 2015-09-09 11:51, Paul Durrant wrote:
>> -----Original Message-----
>> From: win-pv-devel-bounces@xxxxxxxxxxxxxxxxxxxx [mailto:win-pv-devel-
>> bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf Of Paul Durrant
>> Sent: 09 September 2015 10:18
>> To: RafaÅ WojdyÅa; win-pv-devel@xxxxxxxxxxxxxxxxxxxx
>> Subject: Re: [win-pv-devel] Xenbus hashtable usage
>>
>>> -----Original Message-----
>>> From: RafaÅ WojdyÅa [mailto:omeg@xxxxxxxxxxxxxxxxxxxxxx]
>>> Sent: 09 September 2015 10:17
>>> To: Paul Durrant; win-pv-devel@xxxxxxxxxxxxxxxxxxxx
>>> Subject: Re: [win-pv-devel] Xenbus hashtable usage
>>>
>>> On 2015-09-09 10:34, Paul Durrant wrote:
>>>>> -----Original Message-----
>>>>> From: win-pv-devel-bounces@xxxxxxxxxxxxxxxxxxxx [mailto:win-pv-
>> devel-
>>>>> bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf Of Rafal Wojdyla
>>>>> Sent: 09 September 2015 01:44
>>>>> To: win-pv-devel@xxxxxxxxxxxxxxxxxxxx
>>>>> Subject: [win-pv-devel] Xenbus hashtable usage
>>>>>
>>>>> Is the hash table from hash_table.c supposed to accept arbitrary key
>>>>> values?
>>
>> Ok, cool. I'll get a fix together a.s.a.p.
>>
> 
> I think this should do it:
> 
> diff --git a/src/xenbus/hash_table.c b/src/xenbus/hash_table.c
> index a9c1b79..c7c6101 100644
> --- a/src/xenbus/hash_table.c
> +++ b/src/xenbus/hash_table.c
> @@ -90,7 +90,7 @@ HashTableHash(
> 
>          Accumulator = (Accumulator << 4) + Array[Index];
> 
> -        Overflow = Accumulator & 0x00000f00;
> +        Overflow = Accumulator & 0x0000ff00;
>          if (Overflow != 0) {
>              Accumulator ^= Overflow >> 8;
>              Accumulator ^= Overflow;
> 
> Can you test?
> 
>   Paul
> 
This indeed seems to fix the issue, thanks.

>>   Paul
>>
>>>>
>>>> That's the idea. What are you intending to do with it? I have been
>>> wondering about exposing it as an interface.
>>>>
>>> I wanted to use it for storing address <-> map handles for gnttab as you
>>> suggested.
>>>
>>>>> I've been tripping the assertion in HashTableHash() on keys that
>>>>> were 64bit addresses.
>>>>>
>>>>
>>>> That sounds like a straightforward bug then. I'll have a look.
>>>>
>>>> Cheers,
>>>>
>>>>     Paul
>>>>


-- 
RafaÅ WojdyÅa
Qubes Tools for Windows developer
https://www.qubes-os.org/

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