linux-kernel - Re: [PATCH v1 03/16] powerpc/32: move LOAD_MSR_KERNEL() into head

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Date:   Mon, 11 Feb 2019 07:26:51 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v1 03/16] powerpc/32: move LOAD_MSR_KERNEL() into
 head_32.h and use it



Le 11/02/2019 à 01:21, Benjamin Herrenschmidt a écrit :
> On Fri, 2019-02-08 at 12:52 +0000, Christophe Leroy wrote:
>>   /*
>> + * MSR_KERNEL is > 0x8000 on 4xx/Book-E since it include MSR_CE.
>> + */
>> +.macro __LOAD_MSR_KERNEL r, x
>> +.if \x >= 0x8000
>> +       lis \r, (\x)@h
>> +       ori \r, \r, (\x)@l
>> +.else
>> +       li \r, (\x)
>> +.endif
>> +.endm
>> +#define LOAD_MSR_KERNEL(r, x) __LOAD_MSR_KERNEL r, x
>> +
> 
> You changed the limit from >= 0x10000 to >= 0x8000 without a
> corresponding explanation as to why...

Yes, the existing LOAD_MSR_KERNEL() was buggy because 'li' takes a 
signed u16, ie between -0x8000 and 0x7999.

By chance it was working because until now nobody was trying to set 
MSR_KERNEL | MSR_EE.

Christophe