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authorMichael Ellerman <michael@ellerman.id.au>2010-01-28 13:23:22 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2010-03-09 11:52:52 +1100
commit1426d5a3bd07589534286375998c0c8c6fdc5260 (patch)
treefade4f3afd6324b46e27f3c8702935a7edc2fe21 /arch/powerpc/platforms
parent59603b9ae426e968d452f9325cdcff308573dee7 (diff)
powerpc: Dynamically allocate pacas
On 64-bit kernels we currently have a 512 byte struct paca_struct for each cpu (usually just called "the paca"). Currently they are statically allocated, which means a kernel built for a large number of cpus will waste a lot of space if it's booted on a machine with few cpus. We can avoid that by only allocating the number of pacas we need at boot. However this is complicated by the fact that we need to access the paca before we know how many cpus there are in the system. The solution is to dynamically allocate enough space for NR_CPUS pacas, but then later in boot when we know how many cpus we have, we free any unused pacas. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/platforms')
-rw-r--r--arch/powerpc/platforms/iseries/exception.S25
1 files changed, 16 insertions, 9 deletions
diff --git a/arch/powerpc/platforms/iseries/exception.S b/arch/powerpc/platforms/iseries/exception.S
index 5369653dcf6..fba5bf91507 100644
--- a/arch/powerpc/platforms/iseries/exception.S
+++ b/arch/powerpc/platforms/iseries/exception.S
@@ -43,17 +43,14 @@ system_reset_iSeries:
LOAD_REG_ADDR(r23, alpaca)
li r0,ALPACA_SIZE
sub r23,r13,r23
- divdu r23,r23,r0 /* r23 has cpu number */
- LOAD_REG_ADDR(r13, paca)
- mulli r0,r23,PACA_SIZE
- add r13,r13,r0
- mtspr SPRN_SPRG_PACA,r13 /* Save it away for the future */
- mfmsr r24
- ori r24,r24,MSR_RI
- mtmsrd r24 /* RI on */
- mr r24,r23
+ divdu r24,r23,r0 /* r24 has cpu number */
cmpwi 0,r24,0 /* Are we processor 0? */
bne 1f
+ LOAD_REG_ADDR(r13, boot_paca)
+ mtspr SPRN_SPRG_PACA,r13 /* Save it away for the future */
+ mfmsr r23
+ ori r23,r23,MSR_RI
+ mtmsrd r23 /* RI on */
b .__start_initialization_iSeries /* Start up the first processor */
1: mfspr r4,SPRN_CTRLF
li r5,CTRL_RUNLATCH /* Turn off the run light */
@@ -86,6 +83,16 @@ system_reset_iSeries:
#endif
2:
+ /* Load our paca now that it's been allocated */
+ LOAD_REG_ADDR(r13, paca)
+ ld r13,0(r13)
+ mulli r0,r24,PACA_SIZE
+ add r13,r13,r0
+ mtspr SPRN_SPRG_PACA,r13 /* Save it away for the future */
+ mfmsr r23
+ ori r23,r23,MSR_RI
+ mtmsrd r23 /* RI on */
+
HMT_LOW
#ifdef CONFIG_SMP
lbz r23,PACAPROCSTART(r13) /* Test if this processor