Messages in this thread | | | Date | Wed, 17 Jun 2015 13:53:52 +0800 | From | Zhu Guihua <> | Subject | Re: [PATCH V1] x86, espfix: postpone the initialization of espfix stack for AP |
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Any feedback about this?
On 06/04/2015 05:45 PM, Gu Zheng wrote: > The following lockdep warning occurrs when running with latest kernel: > [ 3.178000] ------------[ cut here ]------------ > [ 3.183000] WARNING: CPU: 128 PID: 0 at kernel/locking/lockdep.c:2755 lockdep_trace_alloc+0xdd/0xe0() > [ 3.193000] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)) > [ 3.199000] Modules linked in: > > [ 3.203000] CPU: 128 PID: 0 Comm: swapper/128 Not tainted 4.1.0-rc3 #70 > [ 3.221000] 0000000000000000 2d6601fb3e6d4e4c ffff88086fd5fc38 ffffffff81773f0a > [ 3.230000] 0000000000000000 ffff88086fd5fc90 ffff88086fd5fc78 ffffffff8108c85a > [ 3.238000] ffff88086fd60000 0000000000000092 ffff88086fd60000 00000000000000d0 > [ 3.246000] Call Trace: > [ 3.249000] [<ffffffff81773f0a>] dump_stack+0x4c/0x65 > [ 3.255000] [<ffffffff8108c85a>] warn_slowpath_common+0x8a/0xc0 > [ 3.261000] [<ffffffff8108c8e5>] warn_slowpath_fmt+0x55/0x70 > [ 3.268000] [<ffffffff810ee24d>] lockdep_trace_alloc+0xdd/0xe0 > [ 3.274000] [<ffffffff811cda0d>] __alloc_pages_nodemask+0xad/0xca0 > [ 3.281000] [<ffffffff810ec7ad>] ? __lock_acquire+0xf6d/0x1560 > [ 3.288000] [<ffffffff81219c8a>] alloc_page_interleave+0x3a/0x90 > [ 3.295000] [<ffffffff8121b32d>] alloc_pages_current+0x17d/0x1a0 > [ 3.301000] [<ffffffff811c869e>] ? __get_free_pages+0xe/0x50 > [ 3.308000] [<ffffffff811c869e>] __get_free_pages+0xe/0x50 > [ 3.314000] [<ffffffff8102640b>] init_espfix_ap+0x17b/0x320 > [ 3.320000] [<ffffffff8105c691>] start_secondary+0xf1/0x1f0 > [ 3.327000] ---[ end trace 1b3327d9d6a1d62c ]--- > > As we alloc pages with GFP_KERNEL in init_espfix_ap() which is called > before enabled local irq, and the lockdep sub-system considers this > behaviour as allocating memory with GFP_FS with local irq disabled, > then trigger the warning as mentioned about. > > Though we could allocate them on the boot CPU side and hand them over to > the secondary CPU, but it seemes a bit waste if some of cpus are offline. > As thers is no need to these pages(espfix stack) until we try to run user > code, so we postpone the initialization of espfix stack, and let the boot > up routine init the espfix stack for the target cpu after it booted to > avoid the noise. > > Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com> > --- > v1: > Alloc the page on the node the target CPU is on. > RFC: > Let the boot up routine init the espfix stack for the target cpu after it > booted. > --- > --- > arch/x86/include/asm/espfix.h | 2 +- > arch/x86/kernel/espfix_64.c | 28 ++++++++++++++++------------ > arch/x86/kernel/smpboot.c | 14 +++++++------- > 3 files changed, 24 insertions(+), 20 deletions(-) > > diff --git a/arch/x86/include/asm/espfix.h b/arch/x86/include/asm/espfix.h > index 99efebb..ca3ce9a 100644 > --- a/arch/x86/include/asm/espfix.h > +++ b/arch/x86/include/asm/espfix.h > @@ -9,7 +9,7 @@ DECLARE_PER_CPU_READ_MOSTLY(unsigned long, espfix_stack); > DECLARE_PER_CPU_READ_MOSTLY(unsigned long, espfix_waddr); > > extern void init_espfix_bsp(void); > -extern void init_espfix_ap(void); > +extern void init_espfix_ap(int cpu); > > #endif /* CONFIG_X86_64 */ > > diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c > index f5d0730..e397583 100644 > --- a/arch/x86/kernel/espfix_64.c > +++ b/arch/x86/kernel/espfix_64.c > @@ -131,25 +131,24 @@ void __init init_espfix_bsp(void) > init_espfix_random(); > > /* The rest is the same as for any other processor */ > - init_espfix_ap(); > + init_espfix_ap(0); > } > > -void init_espfix_ap(void) > +void init_espfix_ap(int cpu) > { > - unsigned int cpu, page; > + unsigned int page; > unsigned long addr; > pud_t pud, *pud_p; > pmd_t pmd, *pmd_p; > pte_t pte, *pte_p; > - int n; > + int n, node; > void *stack_page; > pteval_t ptemask; > > /* We only have to do this once... */ > - if (likely(this_cpu_read(espfix_stack))) > + if (likely(per_cpu(espfix_stack, cpu))) > return; /* Already initialized */ > > - cpu = smp_processor_id(); > addr = espfix_base_addr(cpu); > page = cpu/ESPFIX_STACKS_PER_PAGE; > > @@ -165,12 +164,15 @@ void init_espfix_ap(void) > if (stack_page) > goto unlock_done; > > + node = cpu_to_node(cpu); > ptemask = __supported_pte_mask; > > pud_p = &espfix_pud_page[pud_index(addr)]; > pud = *pud_p; > if (!pud_present(pud)) { > - pmd_p = (pmd_t *)__get_free_page(PGALLOC_GFP); > + struct page *page = alloc_pages_node(node, PGALLOC_GFP, 0); > + > + pmd_p = (pmd_t *)page_address(page); > pud = __pud(__pa(pmd_p) | (PGTABLE_PROT & ptemask)); > paravirt_alloc_pmd(&init_mm, __pa(pmd_p) >> PAGE_SHIFT); > for (n = 0; n < ESPFIX_PUD_CLONES; n++) > @@ -180,7 +182,9 @@ void init_espfix_ap(void) > pmd_p = pmd_offset(&pud, addr); > pmd = *pmd_p; > if (!pmd_present(pmd)) { > - pte_p = (pte_t *)__get_free_page(PGALLOC_GFP); > + struct page *page = alloc_pages_node(node, PGALLOC_GFP, 0); > + > + pte_p = (pte_t *)page_address(page); > pmd = __pmd(__pa(pte_p) | (PGTABLE_PROT & ptemask)); > paravirt_alloc_pte(&init_mm, __pa(pte_p) >> PAGE_SHIFT); > for (n = 0; n < ESPFIX_PMD_CLONES; n++) > @@ -188,7 +192,7 @@ void init_espfix_ap(void) > } > > pte_p = pte_offset_kernel(&pmd, addr); > - stack_page = (void *)__get_free_page(GFP_KERNEL); > + stack_page = page_address(alloc_pages_node(node, GFP_KERNEL, 0)); > pte = __pte(__pa(stack_page) | (__PAGE_KERNEL_RO & ptemask)); > for (n = 0; n < ESPFIX_PTE_CLONES; n++) > set_pte(&pte_p[n*PTE_STRIDE], pte); > @@ -199,7 +203,7 @@ void init_espfix_ap(void) > unlock_done: > mutex_unlock(&espfix_init_mutex); > done: > - this_cpu_write(espfix_stack, addr); > - this_cpu_write(espfix_waddr, (unsigned long)stack_page > - + (addr & ~PAGE_MASK)); > + per_cpu(espfix_stack, cpu) = addr; > + per_cpu(espfix_waddr, cpu) = (unsigned long)stack_page > + + (addr & ~PAGE_MASK); > } > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index 50e547e..e9fdd0e 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -240,13 +240,6 @@ static void notrace start_secondary(void *unused) > check_tsc_sync_target(); > > /* > - * Enable the espfix hack for this CPU > - */ > -#ifdef CONFIG_X86_ESPFIX64 > - init_espfix_ap(); > -#endif > - > - /* > * We need to hold vector_lock so there the set of online cpus > * does not change while we are assigning vectors to cpus. Holding > * this lock ensures we don't half assign or remove an irq from a cpu. > @@ -901,6 +894,13 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle) > } > } > > + /* > + * Enable the espfix hack for this CPU > + */ > +#ifdef CONFIG_X86_ESPFIX64 > + init_espfix_ap(cpu); > +#endif > + > /* mark "stuck" area as not stuck */ > *trampoline_status = 0; >
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