Re: [PATCH] mm/ksm: ignore STABLE_FLAG of rmap_item->address in rmap_walk_ksm
From: Jia He
Date: Thu May 03 2018 - 09:23:29 EST
On 5/3/2018 6:44 PM, Claudio Imbrenda Wrote:
On Thu, 3 May 2018 16:34:48 +0800
Jia He <hejianet@xxxxxxxxx> wrote:
In our armv8a server(QDF2400), I noticed a WARN_ON caused by PAGE_SIZE
unaligned for rmap_item->address.
--------------------------begin--------------------------------------
[ 410.853828] WARNING: CPU: 4 PID: 4641 at
arch/arm64/kvm/../../../virt/kvm/arm/mmu.c:1826
kvm_age_hva_handler+0xc0/0xc8
[ 410.864518] Modules linked in: vhost_net vhost tap xt_CHECKSUM
ipt_MASQUERADE nf_nat_masquerade_ipv4 ip6t_rpfilter ipt_REJECT
nf_reject_ipv4 ip6t_REJECT nf_reject_ipv6 xt_conntrack ip_set
nfnetlink ebtable_nat ebtable_broute bridge stp llc ip6table_nat
nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle
ip6table_security ip6table_raw iptable_nat nf_conntrack_ipv4
nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle
iptable_security iptable_raw ebtable_filter ebtables ip6table_filter
ip6_tables iptable_filter rpcrdma ib_isert iscsi_target_mod ib_iser
libiscsi scsi_transport_iscsi ib_srpt target_core_mod ib_srp
scsi_transport_srp ib_ipoib rdma_ucm ib_ucm ib_umad rdma_cm ib_cm
iw_cm mlx5_ib vfat fat ib_uverbs dm_mirror dm_region_hash ib_core
dm_log dm_mod crc32_ce ipmi_ssif sg nfsd [ 410.935101] auth_rpcgss
nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c mlx5_core ixgbe
mlxfw devlink mdio ahci_platform libahci_platform qcom_emac libahci
hdma hdma_mgmt i2c_qup [ 410.951369] CPU: 4 PID: 4641 Comm: memhog
Tainted: G W 4.17.0-rc3+ #8
[ 410.959104] Hardware name: <snip for confidential issues>
[ 410.969791] pstate: 80400005 (Nzcv daif +PAN -UAO)
[ 410.974575] pc : kvm_age_hva_handler+0xc0/0xc8
[ 410.979012] lr : handle_hva_to_gpa+0xa8/0xe0
[ 410.983274] sp : ffff801761553290
[ 410.986581] x29: ffff801761553290 x28: 0000000000000000
[ 410.991888] x27: 0000000000000002 x26: 0000000000000000
[ 410.997195] x25: ffff801765430058 x24: ffff0000080b5608
[ 411.002501] x23: 0000000000000000 x22: ffff8017ccb84000
[ 411.007807] x21: 0000000003ff0000 x20: ffff8017ccb84000
[ 411.013113] x19: 000000000000fe00 x18: ffff000008fb3c08
[ 411.018419] x17: 0000000000000000 x16: 0060001645820bd3
[ 411.023725] x15: ffff80176aacbc08 x14: 0000000000000000
[ 411.029031] x13: 0000000000000040 x12: 0000000000000228
[ 411.034337] x11: 0000000000000000 x10: 0000000000000000
[ 411.039643] x9 : 0000000000000010 x8 : 0000000000000004
[ 411.044949] x7 : 0000000000000000 x6 : 00008017f0770000
[ 411.050255] x5 : 0000fffda59f0200 x4 : 0000000000000000
[ 411.055561] x3 : 0000000000000000 x2 : 000000000000fe00
[ 411.060867] x1 : 0000000003ff0000 x0 : 0000000020000000
[ 411.066173] Call trace:
[ 411.068614] kvm_age_hva_handler+0xc0/0xc8
[ 411.072703] handle_hva_to_gpa+0xa8/0xe0
[ 411.076619] kvm_age_hva+0x4c/0xe8
[ 411.080014] kvm_mmu_notifier_clear_flush_young+0x54/0x98
[ 411.085408] __mmu_notifier_clear_flush_young+0x6c/0xa0
[ 411.090627] page_referenced_one+0x154/0x1d8
[ 411.094890] rmap_walk_ksm+0x12c/0x1d0
[ 411.098632] rmap_walk+0x94/0xa0
[ 411.101854] page_referenced+0x194/0x1b0
[ 411.105770] shrink_page_list+0x674/0xc28
[ 411.109772] shrink_inactive_list+0x26c/0x5b8
[ 411.114122] shrink_node_memcg+0x35c/0x620
[ 411.118211] shrink_node+0x100/0x430
[ 411.121778] do_try_to_free_pages+0xe0/0x3a8
[ 411.126041] try_to_free_pages+0xe4/0x230
[ 411.130045] __alloc_pages_nodemask+0x564/0xdc0
[ 411.134569] alloc_pages_vma+0x90/0x228
[ 411.138398] do_anonymous_page+0xc8/0x4d0
[ 411.142400] __handle_mm_fault+0x4a0/0x508
[ 411.146489] handle_mm_fault+0xf8/0x1b0
[ 411.150321] do_page_fault+0x218/0x4b8
[ 411.154064] do_translation_fault+0x90/0xa0
[ 411.158239] do_mem_abort+0x68/0xf0
[ 411.161721] el0_da+0x24/0x28
---------------------------end---------------------------------------
In rmap_walk_ksm, the rmap_item->address might still have the
STABLE_FLAG, then the start and end in handle_hva_to_gpa might not be
PAGE_SIZE aligned. Thus it causes exceptions in handle_hva_to_gpa on
arm64.
This patch fixes it by ignoring the low bits of rmap_item->address
when doing rmap_walk_ksm.
Signed-off-by: jia.he@xxxxxxxxxxxxxxxx
---
mm/ksm.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/mm/ksm.c b/mm/ksm.c
index e3cbf9a..3f0d980 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -199,6 +199,8 @@ struct rmap_item {
#define SEQNR_MASK 0x0ff /* low bits of unstable tree
seqnr */ #define UNSTABLE_FLAG 0x100 /* is a node of
the unstable tree */ #define STABLE_FLAG 0x200 /* is
listed from the stable tree */ +#define KSM_FLAG_MASK
(SEQNR_MASK|UNSTABLE_FLAG|STABLE_FLAG)
+ /* to mask all the flags */
/* The stable and unstable tree heads */
static struct rb_root one_stable_tree[1] = { RB_ROOT };
@@ -2570,10 +2572,13 @@ void rmap_walk_ksm(struct page *page, struct
rmap_walk_control *rwc) anon_vma_lock_read(anon_vma);
anon_vma_interval_tree_foreach(vmac,
&anon_vma->rb_root, 0, ULONG_MAX) {
+ unsigned long addr;
+
cond_resched();
vma = vmac->vma;
- if (rmap_item->address < vma->vm_start ||
- rmap_item->address >= vma->vm_end)
+
+ addr = rmap_item->address;
why not just: addr = rmap_item->address & ~KSM_FLAG_MASK;
yes, thank you.
Cheers,
Jia
+ if (addr < vma->vm_start || addr >=
vma->vm_end) continue;
/*
* Initially we examine only the vma which
covers this @@ -2587,8 +2592,10 @@ void rmap_walk_ksm(struct page
*page, struct rmap_walk_control *rwc) if (rwc->invalid_vma &&
rwc->invalid_vma(vma, rwc->arg)) continue;
- if (!rwc->rmap_one(page, vma,
- rmap_item->address,
rwc->arg)) {
+ if (addr & STABLE_FLAG)
+ addr &= ~KSM_FLAG_MASK;
then you would not need the IF above, and it would be more readable.
+
+ if (!rwc->rmap_one(page, vma, addr,
rwc->arg)) { anon_vma_unlock_read(anon_vma);
return;
}
best regards,
Claudio Imbrenda
--
Cheers,
Jia