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    Subject[patch] alpha: fix alignment problem in csum_ipv6_magic()
    Hopefully this fixes http://bugzilla.kernel.org/show_bug.cgi?id=8635

    The struct in6_addr passed to csum_ipv6_magic() is 4 byte aligned,
    so we can't use the regular 64-bit loads.
    Since the cost of handling of 4 byte and 1 byte aligned 64-bit data is
    roughly the same, this code can cope with any src/dst [mis]alignment.

    Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>

    Ivan.

    --- 2.6.22-rc4/arch/alpha/lib/ev6-csum_ipv6_magic.S Sun Feb 4 21:44:54 2007
    +++ linux/arch/alpha/lib/ev6-csum_ipv6_magic.S Sun Jun 17 00:41:53 2007
    @@ -46,6 +46,10 @@
    * add the 3 low ushorts together, generating a uint
    * a final add of the 2 lower ushorts
    * truncating the result.
    + *
    + * Misalignment handling added by Ivan Kokshaysky <ink@jurassic.park.msu.ru>
    + * The cost is 16 instructions (~8 cycles), including two extra loads which
    + * may cause additional delay in rare cases (load-load replay traps).
    */

    .globl csum_ipv6_magic
    @@ -55,25 +59,45 @@
    csum_ipv6_magic:
    .prologue 0

    - ldq $0,0($16) # L : Latency: 3
    + ldq_u $0,0($16) # L : Latency: 3
    inslh $18,7,$4 # U : 0000000000AABBCC
    - ldq $1,8($16) # L : Latency: 3
    + ldq_u $1,8($16) # L : Latency: 3
    sll $19,8,$7 # U : U L U L : 0x00000000 00aabb00

    + and $16,7,$6 # E : src misalignment
    + ldq_u $5,15($16) # L : Latency: 3
    zapnot $20,15,$20 # U : zero extend incoming csum
    - ldq $2,0($17) # L : Latency: 3
    - sll $19,24,$19 # U : U L L U : 0x000000aa bb000000
    - inswl $18,3,$18 # U : 000000CCDD000000
    + ldq_u $2,0($17) # L : U L U L : Latency: 3
    +
    + extql $0,$6,$0 # U :
    + extqh $1,$6,$22 # U :
    + ldq_u $3,8($17) # L : Latency: 3
    + sll $19,24,$19 # U : U U L U : 0x000000aa bb000000
    +
    + cmoveq $6,$31,$22 # E : src aligned?
    + ldq_u $23,15($17) # L : Latency: 3
    + or $18,$4,$18 # E : 000000CCDDAABBCC
    + extql $1,$6,$1 # U : U L L U :

    - ldq $3,8($17) # L : Latency: 3
    - bis $18,$4,$18 # E : 000000CCDDAABBCC
    + or $0,$22,$0 # E : 1st src word complete
    + extqh $5,$6,$5 # U :
    addl $19,$7,$19 # E : <sign bits>bbaabb00
    - nop # E : U L U L
    + and $17,7,$6 # E : L U L U : dst misalignment

    + inswl $18,3,$18 # U : 000000CCDD000000
    + or $1,$5,$1 # E : 2nd src word complete
    + extql $2,$6,$2 # U :
    + extqh $3,$6,$22 # U : U L U U :
    +
    + cmoveq $6,$31,$22 # E : dst aligned?
    + extql $3,$6,$3 # U :
    addq $20,$0,$20 # E : begin summing the words
    + extqh $23,$6,$23 # U : L U L U :
    +
    srl $18,16,$4 # U : 0000000000CCDDAA
    + or $2,$22,$2 # E : 1st dst word complete
    zap $19,0x3,$19 # U : <sign bits>bbaa0000
    - nop # E : L U U L
    + or $3,$23,$3 # E : U L U L : 2nd dst word complete

    cmpult $20,$0,$0 # E :
    addq $20,$1,$20 # E :
    --- 2.6.22-rc4/arch/alpha/lib/csum_ipv6_magic.S Sun Feb 4 21:44:54 2007
    +++ linux/arch/alpha/lib/csum_ipv6_magic.S Sun Jun 17 00:29:28 2007
    @@ -7,6 +7,9 @@
    * __u32 len,
    * unsigned short proto,
    * unsigned int csum);
    + *
    + * Misalignment handling (which costs 16 instructions / 8 cycles)
    + * added by Ivan Kokshaysky <ink@jurassic.park.msu.ru>
    */

    .globl csum_ipv6_magic
    @@ -16,37 +19,57 @@
    csum_ipv6_magic:
    .prologue 0

    - ldq $0,0($16) # e0 : load src & dst addr words
    + ldq_u $0,0($16) # e0 : load src & dst addr words
    zapnot $20,15,$20 # .. e1 : zero extend incoming csum
    extqh $18,1,$4 # e0 : byte swap len & proto while we wait
    - ldq $1,8($16) # .. e1 :
    + ldq_u $21,7($16) # .. e1 : handle misalignment

    extbl $18,1,$5 # e0 :
    - ldq $2,0($17) # .. e1 :
    + ldq_u $1,8($16) # .. e1 :
    extbl $18,2,$6 # e0 :
    - ldq $3,8($17) # .. e1 :
    + ldq_u $22,15($16) # .. e1 :

    extbl $18,3,$18 # e0 :
    + ldq_u $2,0($17) # .. e1 :
    sra $4,32,$4 # e0 :
    + ldq_u $23,7($17) # .. e1 :
    +
    + extql $0,$16,$0 # e0 :
    + ldq_u $3,8($17) # .. e1 :
    + extqh $21,$16,$21 # e0 :
    + ldq_u $24,15($17) # .. e1 :
    +
    sll $5,16,$5 # e0 :
    + or $0,$21,$0 # .. e1 : 1st src word complete
    + extql $1,$16,$1 # e0 :
    addq $20,$0,$20 # .. e1 : begin summing the words

    - sll $6,8,$6 # e0 :
    + extqh $22,$16,$22 # e0 :
    cmpult $20,$0,$0 # .. e1 :
    - extwh $19,7,$7 # e0 :
    - or $4,$18,$18 # .. e1 :
    + sll $6,8,$6 # e0 :
    + or $1,$22,$1 # .. e1 : 2nd src word complete

    - extbl $19,1,$19 # e0 :
    + extql $2,$17,$2 # e0 :
    + or $4,$18,$18 # .. e1 :
    + extqh $23,$17,$23 # e0 :
    or $5,$6,$5 # .. e1 :
    - or $18,$5,$18 # e0 : len complete
    - or $19,$7,$19 # .. e1 :

    - sll $19,48,$19 # e0 :
    + extql $3,$17,$3 # e0 :
    + or $2,$23,$2 # .. e1 : 1st dst word complete
    + extqh $24,$17,$24 # e0 :
    + or $18,$5,$18 # .. e1 : len complete
    +
    + extwh $19,7,$7 # e0 :
    + or $3,$24,$3 # .. e1 : 2nd dst word complete
    + extbl $19,1,$19 # e0 :
    addq $20,$1,$20 # .. e1 :
    - sra $19,32,$19 # e0 : proto complete
    +
    + or $19,$7,$19 # e0 :
    cmpult $20,$1,$1 # .. e1 :
    + sll $19,48,$19 # e0 :
    + nop # .. e0 :

    - nop # e0 :
    + sra $19,32,$19 # e0 : proto complete
    addq $20,$2,$20 # .. e1 :
    cmpult $20,$2,$2 # e0 :
    addq $20,$3,$20 # .. e1 :
    @@ -84,7 +107,7 @@ csum_ipv6_magic:
    extwl $0,2,$1 # e0 : fold 17-bit value
    zapnot $0,3,$0 # .. e1 :
    addq $0,$1,$0 # e0 :
    - not $0,$0 # e1 : and complement.
    + not $0,$0 # .. e1 : and complement.

    zapnot $0,3,$0 # e0 :
    ret # .. e1 :
    -
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