In message <39fb8f1aeab9940b86c940b9a5f8e6bd41ec316c.1263368253.git.mich...@ell
erman.id.au> you wrote:
> 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.
>
> Lightly booted on Legacy iSeries & pSeries LPAR.
This is broken on 32bit CPUs. Dies at compile time with
mpc86xx_defconfig. No paca on 32bit :-(
/home/mikey/src/linux-2.6-ozlabs/arch/powerpc/kernel/prom.c: In function
‘early_init_devtree’:
/home/mikey/src/linux-2.6-ozlabs/arch/powerpc/kernel/prom.c:1227: error:
implicit declaration of function ‘allocate_pacas’
make[2]: *** [arch/powerpc/kernel/prom.o] Error 1
make[2]: *** Waiting for unfinished jobs....
/home/mikey/src/linux-2.6-ozlabs/arch/powerpc/kernel/setup-common.c: In
function ‘smp_setup_cpu_maps’:
/home/mikey/src/linux-2.6-ozlabs/arch/powerpc/kernel/setup-common.c:497: error:
implicit declaration of function ‘free_unused_pacas’
make[2]: *** [arch/powerpc/kernel/setup-common.o] Error 1
make[1]: *** [arch/powerpc/kernel] Error 2
make[1]: *** Waiting for unfinished jobs....
Mikey
>
> Signed-off-by: Michael Ellerman <mich...@ellerman.id.au>
> ---
> arch/powerpc/include/asm/paca.h | 8 ++-
> arch/powerpc/kernel/head_64.S | 6 +-
> arch/powerpc/kernel/paca.c | 93 +++++++++++++++++++++-----
--
> arch/powerpc/kernel/prom.c | 2 +
> arch/powerpc/kernel/setup-common.c | 2 +
> arch/powerpc/kernel/setup_64.c | 12 ++--
> arch/powerpc/platforms/iseries/exception.S | 25 +++++---
> 7 files changed, 106 insertions(+), 42 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.
h
> index 5e9b4ef..41e0f17 100644
> --- a/arch/powerpc/include/asm/paca.h
> +++ b/arch/powerpc/include/asm/paca.h
> @@ -14,6 +14,7 @@
> #define _ASM_POWERPC_PACA_H
> #ifdef __KERNEL__
>
> +#include <linux/init.h>
> #include <asm/types.h>
> #include <asm/lppaca.h>
> #include <asm/mmu.h>
> @@ -140,8 +141,11 @@ struct paca_struct {
> #endif
> };
>
> -extern struct paca_struct paca[];
> -extern void initialise_pacas(void);
> +extern struct paca_struct *paca;
> +extern __initdata struct paca_struct boot_paca;
> +extern void allocate_pacas(void);
> +extern void initialise_paca(struct paca_struct *new_paca, int cpu);
> +extern void free_unused_pacas(void);
>
> #endif /* __KERNEL__ */
> #endif /* _ASM_POWERPC_PACA_H */
> diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
> index 9258074..b24b700 100644
> --- a/arch/powerpc/kernel/head_64.S
> +++ b/arch/powerpc/kernel/head_64.S
> @@ -219,7 +219,8 @@ generic_secondary_common_init:
> * physical cpu id in r24, we need to search the pacas to find
> * which logical id maps to our physical one.
> */
> - LOAD_REG_ADDR(r13, paca) /* Get base vaddr of paca array */
> + LOAD_REG_ADDR(r13, paca) /* Load paca pointer */
> + ld r13,0(r13) /* Get base vaddr of paca array */
> li r5,0 /* logical cpu id */
> 1: lhz r6,PACAHWCPUID(r13) /* Load HW procid from paca */
> cmpw r6,r24 /* Compare to our id */
> @@ -536,7 +537,8 @@ _GLOBAL(pmac_secondary_start)
> mtmsrd r3 /* RI on */
>
> /* Set up a paca value for this processor. */
> - LOAD_REG_ADDR(r4,paca) /* Get base vaddr of paca array */
> + LOAD_REG_ADDR(r4,paca) /* Load paca pointer */
> + ld r4,0(r4) /* Get base vaddr of paca array */
> mulli r13,r24,PACA_SIZE /* Calculate vaddr of right paca */
> add r13,r13,r4 /* for this processor. */
> mtspr SPRN_SPRG_PACA,r13 /* Save vaddr of paca in an SPRG*/
> diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
> index d16b1ea..0c40c6f 100644
> --- a/arch/powerpc/kernel/paca.c
> +++ b/arch/powerpc/kernel/paca.c
> @@ -9,11 +9,15 @@
>
> #include <linux/threads.h>
> #include <linux/module.h>
> +#include <linux/lmb.h>
>
> +#include <asm/firmware.h>
> #include <asm/lppaca.h>
> #include <asm/paca.h>
> #include <asm/sections.h>
> #include <asm/pgtable.h>
> +#include <asm/iseries/lpar_map.h>
> +#include <asm/iseries/hv_types.h>
>
> /* This symbol is provided by the linker - let it fill in the paca
> * field correctly */
> @@ -70,37 +74,82 @@ struct slb_shadow slb_shadow[] __cacheline_aligned = {
> * processors. The processor VPD array needs one entry per physical
> * processor (not thread).
> */
> -struct paca_struct paca[NR_CPUS];
> +struct paca_struct *paca;
> EXPORT_SYMBOL(paca);
>
> -void __init initialise_pacas(void)
> -{
> - int cpu;
> +struct paca_struct boot_paca;
>
> - /* The TOC register (GPR2) points 32kB into the TOC, so that 64kB
> - * of the TOC can be addressed using a single machine instruction.
> - */
> +void __init initialise_paca(struct paca_struct *new_paca, int cpu)
> +{
> + /* The TOC register (GPR2) points 32kB into the TOC, so that 64kB
> + * of the TOC can be addressed using a single machine instruction.
> + */
> unsigned long kernel_toc = (unsigned long)(&__toc_start) + 0x8000UL;
>
> - /* Can't use for_each_*_cpu, as they aren't functional yet */
> - for (cpu = 0; cpu < NR_CPUS; cpu++) {
> - struct paca_struct *new_paca = &paca[cpu];
> -
> #ifdef CONFIG_PPC_BOOK3S
> - new_paca->lppaca_ptr = &lppaca[cpu];
> + new_paca->lppaca_ptr = &lppaca[cpu];
> #else
> - new_paca->kernel_pgd = swapper_pg_dir;
> + new_paca->kernel_pgd = swapper_pg_dir;
> #endif
> - new_paca->lock_token = 0x8000;
> - new_paca->paca_index = cpu;
> - new_paca->kernel_toc = kernel_toc;
> - new_paca->kernelbase = (unsigned long) _stext;
> - new_paca->kernel_msr = MSR_KERNEL;
> - new_paca->hw_cpu_id = 0xffff;
> - new_paca->__current = &init_task;
> + new_paca->lock_token = 0x8000;
> + new_paca->paca_index = cpu;
> + new_paca->kernel_toc = kernel_toc;
> + new_paca->kernelbase = (unsigned long) _stext;
> + new_paca->kernel_msr = MSR_KERNEL;
> + new_paca->hw_cpu_id = 0xffff;
> + new_paca->__current = &init_task;
> #ifdef CONFIG_PPC_STD_MMU_64
> - new_paca->slb_shadow_ptr = &slb_shadow[cpu];
> + new_paca->slb_shadow_ptr = &slb_shadow[cpu];
> #endif /* CONFIG_PPC_STD_MMU_64 */
> +}
> +
> +static int __initdata paca_size;
> +
> +void __init allocate_pacas(void)
> +{
> + int nr_cpus, cpu, limit;
> +
> + /*
> + * We can't take SLB misses on the paca, and we want to access them
> + * in real mode, so allocate them within the RMA and also within
> + * the first segment. On iSeries they must be within the area mapped
> + * by the HV, which is HvPagesToMap * HVPAGESIZE bytes.
> + */
> + limit = min(0x10000000ULL, lmb.rmo_size);
> + if (firmware_has_feature(FW_FEATURE_ISERIES))
> + limit = min(limit, HvPagesToMap * HVPAGESIZE);
> +
> + nr_cpus = NR_CPUS;
> + /* On iSeries we know we can never have more than 64 cpus */
> + if (firmware_has_feature(FW_FEATURE_ISERIES))
> + nr_cpus = min(64, nr_cpus);
> +
> + paca_size = PAGE_ALIGN(sizeof(struct paca_struct) * nr_cpus);
> +
> + paca = __va(lmb_alloc_base(paca_size, PAGE_SIZE, limit));
> + memset(paca, 0, paca_size);
> +
> + printk(KERN_DEBUG "Allocated %u bytes for %d pacas at %p\n",
> + paca_size, nr_cpus, paca);
> +
> + /* Can't use for_each_*_cpu, as they aren't functional yet */
> + for (cpu = 0; cpu < nr_cpus; cpu++)
> + initialise_paca(&paca[cpu], cpu);
> +}
> +
> +void __init free_unused_pacas(void)
> +{
> + int new_size;
> +
> + new_size = PAGE_ALIGN(sizeof(struct paca_struct) * num_possible_cpus())
;
> +
> + if (new_size >= paca_size)
> + return;
> +
> + lmb_free(__pa(paca) + new_size, paca_size - new_size);
> +
> + printk(KERN_DEBUG "Freed %u bytes for unused pacas\n",
> + paca_size - new_size);
>
> - }
> + paca_size = new_size;
> }
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index 4ec3008..50c3c55 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -1224,6 +1224,8 @@ void __init early_init_devtree(void *params)
> * FIXME .. and the initrd too? */
> move_device_tree();
>
> + allocate_pacas();
> +
> DBG("Scanning CPUs ...\n");
>
> /* Retreive CPU related informations from the flat tree
> diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-c
ommon.c
> index 03dd6a2..5df0f6a 100644
> --- a/arch/powerpc/kernel/setup-common.c
> +++ b/arch/powerpc/kernel/setup-common.c
> @@ -493,6 +493,8 @@ void __init smp_setup_cpu_maps(void)
> * here will have to be reworked
> */
> cpu_init_thread_core_maps(nthreads);
> +
> + free_unused_pacas();
> }
> #endif /* CONFIG_SMP */
>
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index 6568406..6354739 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -144,9 +144,9 @@ early_param("smt-enabled", early_smt_enabled);
> #endif /* CONFIG_SMP */
>
> /* Put the paca pointer into r13 and SPRG_PACA */
> -void __init setup_paca(int cpu)
> +static void __init setup_paca(struct paca_struct *new_paca)
> {
> - local_paca = &paca[cpu];
> + local_paca = new_paca;
> mtspr(SPRN_SPRG_PACA, local_paca);
> #ifdef CONFIG_PPC_BOOK3E
> mtspr(SPRN_SPRG_TLB_EXFRAME, local_paca->extlb);
> @@ -176,14 +176,12 @@ void __init early_setup(unsigned long dt_ptr)
> {
> /* -------- printk is _NOT_ safe to use here ! ------- */
>
> - /* Fill in any unititialised pacas */
> - initialise_pacas();
> -
> /* Identify CPU type */
> identify_cpu(0, mfspr(SPRN_PVR));
>
> /* Assume we're on cpu 0 for now. Don't write to the paca yet! */
> - setup_paca(0);
> + initialise_paca(&boot_paca, 0);
> + setup_paca(&boot_paca);
>
> /* Initialize lockdep early or else spinlocks will blow */
> lockdep_init();
> @@ -203,7 +201,7 @@ void __init early_setup(unsigned long dt_ptr)
> early_init_devtree(__va(dt_ptr));
>
> /* Now we know the logical id of our boot cpu, setup the paca. */
> - setup_paca(boot_cpuid);
> + setup_paca(&paca[boot_cpuid]);
>
> /* Fix up paca fields required for the boot cpu */
> get_paca()->cpu_start = 1;
> diff --git a/arch/powerpc/platforms/iseries/exception.S b/arch/powerpc/platfo
rms/iseries/exception.S
> index 5369653..fba5bf9 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
> --
> 1.6.3.3
>
> _______________________________________________
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