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Date: Tue, 20 Apr 2010 13:17:59 +0800
From: Wu Fengguang <fengguang.wu@...el.com>
To: Haicheng Li <haicheng.li@...ux.intel.com>
Cc: "ak@...ux.intel.com" <ak@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"dnelson@...hat.com" <dnelson@...hat.com>,
Andi Kleen <andi@...stfloor.org>,
"Li, Haicheng" <haicheng.li@...el.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [BUGFIX] [PATCH v2] x86: update all PGDs for direct mapping
changes on 64bit.
Hi Haicheng,
On Tue, Apr 20, 2010 at 11:28:06AM +0800, Haicheng Li wrote:
> Hello,
>
> I revised the patch to fix a problem pointed out by Dean Nelson that
> "__init_extra_mapping() passes physical addresses to sync_global_pgds()?.
>
> Dean, would you like to add your reviewed-by: line to this patch?
>
> Any other comments? below BUG will definitely happen when hotadding a large
> enough memory to x86 system, so we need to fix it ASAP, even for .32 kernel.
> thanks.
>
> ---
> This patch is to fix a kernel BUG() found in our recent CPU/MEM hotplug testing:
>
> [ 1139.243192] BUG: soft lockup - CPU#0 stuck for 61s! [bash:6534]
> [ 1139.243195] Modules linked in: ipv6 autofs4 rfcomm l2cap crc16 bluetooth rfkill binfmt_misc
> dm_mirror dm_region_hash dm_log dm_multipath dm_mod video output sbs sbshc fan battery ac parport_pc
> lp parport joydev usbhid processor thermal thermal_sys container button rtc_cmos rtc_core rtc_lib
> i2c_i801 i2c_core pcspkr uhci_hcd ohci_hcd ehci_hcd usbcore
> [ 1139.243229] irq event stamp: 8538759
> [ 1139.243230] hardirqs last enabled at (8538759): [<ffffffff8100c3fc>] restore_args+0x0/0x30
> [ 1139.243236] hardirqs last disabled at (8538757): [<ffffffff810422df>] __do_softirq+0x106/0x146
> [ 1139.243240] softirqs last enabled at (8538758): [<ffffffff81042310>] __do_softirq+0x137/0x146
> [ 1139.243245] softirqs last disabled at (8538743): [<ffffffff8100cb5c>] call_softirq+0x1c/0x34
> [ 1139.243249] CPU 0:
> [ 1139.243250] Modules linked in: ipv6 autofs4 rfcomm l2cap crc16 bluetooth rfkill binfmt_misc
> dm_mirror dm_region_hash dm_log dm_multipath dm_mod video output sbs sbshc fan battery ac parport_pc
> lp parport joydev usbhid processor thermal thermal_sys container button rtc_cmos rtc_core rtc_lib
> i2c_i801 i2c_core pcspkr uhci_hcd ohci_hcd ehci_hcd usbcore
> [ 1139.243284] Pid: 6534, comm: bash Tainted: G M 2.6.32-haicheng-cpuhp #7 QSSC-S4R
> [ 1139.243287] RIP: 0010:[<ffffffff810ace35>] [<ffffffff810ace35>] alloc_arraycache+0x35/0x69
> [ 1139.243292] RSP: 0018:ffff8802799f9d78 EFLAGS: 00010286
> [ 1139.243295] RAX: ffff8884ffc00000 RBX: ffff8802799f9d98 RCX: 0000000000000000
> [ 1139.243297] RDX: 0000000000190018 RSI: 0000000000000001 RDI: ffff8884ffc00010
> [ 1139.243300] RBP: ffffffff8100c34e R08: 0000000000000002 R09: 0000000000000000
> [ 1139.243303] R10: ffffffff8246dda0 R11: 000000d08246dda0 R12: ffff8802599bfff0
> [ 1139.243305] R13: ffff88027904c040 R14: ffff8802799f8000 R15: 0000000000000001
> [ 1139.243308] FS: 00007fe81bfe86e0(0000) GS:ffff88000d800000(0000) knlGS:0000000000000000
> [ 1139.243311] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 1139.243313] CR2: ffff8884ffc00000 CR3: 000000026cf2d000 CR4: 00000000000006f0
> [ 1139.243316] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 1139.243318] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [ 1139.243321] Call Trace:
> [ 1139.243324] [<ffffffff810ace29>] ? alloc_arraycache+0x29/0x69
> [ 1139.243328] [<ffffffff8135004e>] ? cpuup_callback+0x1b0/0x32a
> [ 1139.243333] [<ffffffff8105385d>] ? notifier_call_chain+0x33/0x5b
> [ 1139.243337] [<ffffffff810538a4>] ? __raw_notifier_call_chain+0x9/0xb
> [ 1139.243340] [<ffffffff8134ecfc>] ? cpu_up+0xb3/0x152
> [ 1139.243344] [<ffffffff813388ce>] ? store_online+0x4d/0x75
> [ 1139.243348] [<ffffffff811e53f3>] ? sysdev_store+0x1b/0x1d
> [ 1139.243351] [<ffffffff8110589f>] ? sysfs_write_file+0xe5/0x121
> [ 1139.243355] [<ffffffff810b539d>] ? vfs_write+0xae/0x14a
> [ 1139.243358] [<ffffffff810b587f>] ? sys_write+0x47/0x6f
> [ 1139.243362] [<ffffffff8100b9ab>] ? system_call_fastpath+0x16/0x1b
>
> When memory hotadd/removal happens for a large enough area
> that a new PGD entry is needed for the direct mapping, the PGDs
> of other processes would not get updated. This leads to some CPUs
> oopsing when they have to access the unmapped areas.
>
> This patch makes sure to always replicate new direct mapping PGD entries
> to the PGDs of all processes.
>
> v2: Fix the problem pointed out by Dean Nelson that
> "__init_extra_mapping() passes physical addresses to sync_global_pgds()?.
>
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> Signed-off-by: Haicheng Li <haicheng.li@...ux.intel.com>
> ---
> arch/x86/mm/init_64.c | 83 ++++++++++++++++++++++++++++++++++++++++---------
> 1 files changed, 68 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index ee41bba..9a3ba23 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -97,6 +97,37 @@ static int __init nonx32_setup(char *str)
> }
> __setup("noexec32=", nonx32_setup);
>
> +
> +/*
> + * When memory was added/removed make sure all the processes MM have
> + * suitable PGD entries in the local PGD level page.
> + * Caller must flush global TLBs if needed (old mapping changed)
> + */
> +static void sync_global_pgds(unsigned long start, unsigned long end)
It seems that this function can reuse code with vmalloc_sync_all().
> +{
> + unsigned long flags;
> + struct page *page;
> + unsigned long addr;
> +
> + spin_lock_irqsave(&pgd_lock, flags);
> + for (addr = start; addr < end; addr += PGDIR_SIZE) {
> + pgd_t *ref_pgd = pgd_offset_k(addr);
> + list_for_each_entry(page, &pgd_list, lru) {
> + pgd_t *pgd_base = page_address(page);
> + pgd_t *pgd = pgd_base + pgd_index(addr);
> +
> + /*
> + * When the state is the same in one other,
> + * assume it's the same everywhere.
> + */
> + if (pgd_base != init_mm.pgd &&
> + !!pgd_none(*pgd) != !!pgd_none(*ref_pgd))
> + set_pgd(pgd, *ref_pgd);
> + }
> + }
> + spin_unlock_irqrestore(&pgd_lock, flags);
> +}
> +
> /*
> * NOTE: This function is marked __ref because it calls __init function
> * (alloc_bootmem_pages). It's safe to do it ONLY when after_bootmem == 0.
> @@ -218,6 +249,9 @@ static void __init __init_extra_mapping(unsigned long phys, unsigned long size,
__init_extra_mapping() is not related to memory hotplug (note: the
__init prefix), so not necessary to change this function?
> pgd_t *pgd;
> pud_t *pud;
> pmd_t *pmd;
> + int pgd_changed = 0;
> + unsigned long start = (unsigned long)__va(phys);
> + unsigned long end = (unsigned long)__va(phys + size);
>
> BUG_ON((phys & ~PMD_MASK) || (size & ~PMD_MASK));
> for (; size; phys += PMD_SIZE, size -= PMD_SIZE) {
> @@ -226,6 +260,7 @@ static void __init __init_extra_mapping(unsigned long phys, unsigned long size,
> pud = (pud_t *) spp_getpage();
> set_pgd(pgd, __pgd(__pa(pud) | _KERNPG_TABLE |
> _PAGE_USER));
> + pgd_changed = 1;
> }
> pud = pud_offset(pgd, (unsigned long)__va(phys));
> if (pud_none(*pud)) {
> @@ -237,6 +272,11 @@ static void __init __init_extra_mapping(unsigned long phys, unsigned long size,
> BUG_ON(!pmd_none(*pmd));
> set_pmd(pmd, __pmd(phys | pgprot_val(prot)));
> }
> + if (pgd_changed) {
> + sync_global_pgds(start, end);
> + /* Might not be needed if the previous mapping was always zero*/
> + __flush_tlb_all();
> + }
> }
>
> void __init init_extra_mapping_wb(unsigned long phys, unsigned long size)
> @@ -534,36 +574,41 @@ kernel_physical_mapping_init(unsigned long start,
> unsigned long end,
> unsigned long page_size_mask)
> {
> -
> + int pgd_changed = 0;
> unsigned long next, last_map_addr = end;
> + unsigned long addr;
>
> start = (unsigned long)__va(start);
> end = (unsigned long)__va(end);
>
> - for (; start < end; start = next) {
> - pgd_t *pgd = pgd_offset_k(start);
> + for (addr = start; addr < end; addr = next) {
> + pgd_t *pgd = pgd_offset_k(addr);
> unsigned long pud_phys;
> pud_t *pud;
>
> - next = (start + PGDIR_SIZE) & PGDIR_MASK;
> + next = (addr + PGDIR_SIZE) & PGDIR_MASK;
> if (next > end)
> next = end;
>
> if (pgd_val(*pgd)) {
> - last_map_addr = phys_pud_update(pgd, __pa(start),
> + last_map_addr = phys_pud_update(pgd, __pa(addr),
> __pa(end), page_size_mask);
> continue;
> }
>
> pud = alloc_low_page(&pud_phys);
> - last_map_addr = phys_pud_init(pud, __pa(start), __pa(next),
> + last_map_addr = phys_pud_init(pud, __pa(addr), __pa(next),
> page_size_mask);
> unmap_low_page(pud);
>
> spin_lock(&init_mm.page_table_lock);
> pgd_populate(&init_mm, pgd, __va(pud_phys));
> spin_unlock(&init_mm.page_table_lock);
> + pgd_changed = 1;
> }
> +
> + if (pgd_changed)
> + sync_global_pgds(start, end);
> __flush_tlb_all();
>
> return last_map_addr;
> @@ -939,35 +984,37 @@ static int __meminitdata node_start;
> int __meminit
> vmemmap_populate(struct page *start_page, unsigned long size, int node)
> {
> - unsigned long addr = (unsigned long)start_page;
> + unsigned long start = (unsigned long)start_page;
> unsigned long end = (unsigned long)(start_page + size);
> - unsigned long next;
> + unsigned long addr, next;
> pgd_t *pgd;
> pud_t *pud;
> pmd_t *pmd;
> + int err = -ENOMEM;
It's not necessary to introduce the "start" and "err" variables.
It helps simplify the patch (or you can put them to another cleanup
only patch).
Thanks,
Fengguang
> - for (; addr < end; addr = next) {
> + for (addr = start; addr < end; addr = next) {
> void *p = NULL;
>
> + err = -ENOMEM;
> pgd = vmemmap_pgd_populate(addr, node);
> if (!pgd)
> - return -ENOMEM;
> + break;
>
> pud = vmemmap_pud_populate(pgd, addr, node);
> if (!pud)
> - return -ENOMEM;
> + break;
>
> if (!cpu_has_pse) {
> next = (addr + PAGE_SIZE) & PAGE_MASK;
> pmd = vmemmap_pmd_populate(pud, addr, node);
>
> if (!pmd)
> - return -ENOMEM;
> + break;
>
> p = vmemmap_pte_populate(pmd, addr, node);
>
> if (!p)
> - return -ENOMEM;
> + break;
>
> addr_end = addr + PAGE_SIZE;
> p_end = p + PAGE_SIZE;
> @@ -980,7 +1027,7 @@ vmemmap_populate(struct page *start_page, unsigned long size, int node)
>
> p = vmemmap_alloc_block_buf(PMD_SIZE, node);
> if (!p)
> - return -ENOMEM;
> + break;
>
> entry = pfn_pte(__pa(p) >> PAGE_SHIFT,
> PAGE_KERNEL_LARGE);
> @@ -1001,9 +1048,15 @@ vmemmap_populate(struct page *start_page, unsigned long size, int node)
> } else
> vmemmap_verify((pte_t *)pmd, node, addr, next);
> }
> + err = 0;
> + }
>
> + if (!err) {
> + sync_global_pgds(start, end);
> + __flush_tlb_all();
> }
> - return 0;
> +
> + return err;
> }
>
> void __meminit vmemmap_populate_print_last(void)
> --
> 1.5.6.1
>
> -haicheng
>
> --
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