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Message-Id: <20070621163501.00903134.akpm@linux-foundation.org> Date: Thu, 21 Jun 2007 16:35:01 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Ivan Kokshaysky <ink@...assic.park.msu.ru> Cc: rth@...ddle.net, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, Dustin Marquess <jailbird@...atraz.fdf.net> Subject: Re: [patch] alpha: fix alignment problem in csum_ipv6_magic() > On Sun, 17 Jun 2007 01:20:20 +0400 Ivan Kokshaysky <ink@...assic.park.msu.ru> wrote: > 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@...assic.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@...assic.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@...assic.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 : In http://bugzilla.kernel.org/show_bug.cgi?id=8659, Dustin is reporting that this patch broke tcp-on-ipv6. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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