linux-kernel - Re: [PATCH v3 06/15] powerpc/32: prepare for CONFIG_VMAP

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Message-ID: <baff8ef3-a3c6-c6e2-732f-4d521d92140b@c-s.fr>
Date:   Fri, 18 Oct 2019 08:46:35 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Andrew Donnellan <ajd@...ux.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, npiggin@...il.com,
        dja@...ens.net
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v3 06/15] powerpc/32: prepare for CONFIG_VMAP_STACK



Le 17/10/2019 à 09:36, Andrew Donnellan a écrit :
> On 10/9/19 7:16 pm, Christophe Leroy wrote:
>> +#if defined(CONFIG_VMAP_STACK) && CONFIG_THREAD_SHIFT < PAGE_SHIFT
>> +#define THREAD_SHIFT        PAGE_SHIFT
>> +#else
>>   #define THREAD_SHIFT        CONFIG_THREAD_SHIFT
>> +#endif
>>
>>   #define THREAD_SIZE        (1 << THREAD_SHIFT)
>>
> 
> Looking at 64-bit book3s: with 64K pages, this results in a THREAD_SIZE 
> that's too large for immediate mode arithmetic operations, which is 
> annoying. Hmm.
> 

Which operation are you thinking about ?

For instance, 'addi' can't be used anymore, but 'addis' can.

Christophe