From 587704efb3dea5685a2f571b75bd3dc47f73fec1 Mon Sep 17 00:00:00 2001 From: Alexander Gordeev Date: Thu, 6 May 2021 16:26:53 +0200 Subject: [PATCH] s390/smp: do not preserve boot CPU lowcore on hotplug Once the kernel is running the boot CPU lowcore becomes freeable and does not differ from the secondary CPU ones in any way. Make use of it and do not preserve the boot CPU lowcore on unplugging. That allows returning unused memory when the boot CPU is offline and makes the code more clear. Signed-off-by: Alexander Gordeev Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik --- arch/s390/kernel/smp.c | 47 ++++++++++++++++-------------------------- 1 file changed, 18 insertions(+), 29 deletions(-) diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index 1e1d61a4d2947..eaca08b1688f1 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -194,20 +194,12 @@ static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu) unsigned long async_stack, nodat_stack, mcck_stack; struct lowcore *lc; - if (pcpu != &pcpu_devices[0]) { - pcpu->lowcore = (struct lowcore *) - __get_free_pages(GFP_KERNEL | GFP_DMA, LC_ORDER); - nodat_stack = __get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER); - if (!pcpu->lowcore || !nodat_stack) - goto out; - } else { - nodat_stack = pcpu->lowcore->nodat_stack - STACK_INIT_OFFSET; - } + lc = (struct lowcore *) __get_free_pages(GFP_KERNEL | GFP_DMA, LC_ORDER); + nodat_stack = __get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER); async_stack = stack_alloc(); mcck_stack = stack_alloc(); - if (!async_stack || !mcck_stack) - goto out_stack; - lc = pcpu->lowcore; + if (!lc || !nodat_stack || !async_stack || !mcck_stack) + goto out; memcpy(lc, &S390_lowcore, 512); memset((char *) lc + 512, 0, sizeof(*lc) - 512); lc->async_stack = async_stack + STACK_INIT_OFFSET; @@ -220,40 +212,37 @@ static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu) lc->return_lpswe = gen_lpswe(__LC_RETURN_PSW); lc->return_mcck_lpswe = gen_lpswe(__LC_RETURN_MCCK_PSW); if (nmi_alloc_per_cpu(lc)) - goto out_stack; + goto out; lowcore_ptr[cpu] = lc; + pcpu->lowcore = lc; pcpu_sigp_retry(pcpu, SIGP_SET_PREFIX, (u32)(unsigned long) lc); return 0; -out_stack: +out: stack_free(mcck_stack); stack_free(async_stack); -out: - if (pcpu != &pcpu_devices[0]) { - free_pages(nodat_stack, THREAD_SIZE_ORDER); - free_pages((unsigned long) pcpu->lowcore, LC_ORDER); - } + free_pages(nodat_stack, THREAD_SIZE_ORDER); + free_pages((unsigned long) lc, LC_ORDER); return -ENOMEM; } static void pcpu_free_lowcore(struct pcpu *pcpu) { - unsigned long async_stack, nodat_stack, mcck_stack, lowcore; - - nodat_stack = pcpu->lowcore->nodat_stack - STACK_INIT_OFFSET; - async_stack = pcpu->lowcore->async_stack - STACK_INIT_OFFSET; - mcck_stack = pcpu->lowcore->mcck_stack - STACK_INIT_OFFSET; - lowcore = (unsigned long) pcpu->lowcore; + unsigned long async_stack, nodat_stack, mcck_stack; + struct lowcore *lc; + lc = pcpu->lowcore; + nodat_stack = lc->nodat_stack - STACK_INIT_OFFSET; + async_stack = lc->async_stack - STACK_INIT_OFFSET; + mcck_stack = lc->mcck_stack - STACK_INIT_OFFSET; pcpu_sigp_retry(pcpu, SIGP_SET_PREFIX, 0); lowcore_ptr[pcpu - pcpu_devices] = NULL; - nmi_free_per_cpu(pcpu->lowcore); + pcpu->lowcore = NULL; + nmi_free_per_cpu(lc); stack_free(async_stack); stack_free(mcck_stack); - if (pcpu == &pcpu_devices[0]) - return; free_pages(nodat_stack, THREAD_SIZE_ORDER); - free_pages(lowcore, LC_ORDER); + free_pages((unsigned long) lc, LC_ORDER); } static void pcpu_prepare_secondary(struct pcpu *pcpu, int cpu) -- 2.30.2