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Subject: Re: [PATCH v3] KVM: arm/arm64: add WARN_ON if size is not PAGE_SIZE
 aligned in unmap_stage2_range
To:     Christoffer Dall <christoffer.dall@arm.com>,
        Marc Zyngier <marc.zyngier@arm.com>,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu
Cc:     Suzuki.Poulose@arm.com, linux-kernel@vger.kernel.org,
        jia.he@hxt-semitech.com
References: <1526871930-1231-1-git-send-email-hejianet@gmail.com>
From:   Jia He <hejianet@gmail.com>
Message-ID: <2c3a60f9-fb75-46bf-e917-005aa85b952c@gmail.com>
Date:   Fri, 8 Jun 2018 17:00:17 +0800
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Ping

Cheers,
Jia

On 5/21/2018 11:05 AM, Jia He Wrote:
> There is a panic in armv8a server(QDF2400) under memory pressure tests
> (start 20 guests and run memhog in the host).
> 
> ---------------------------------begin--------------------------------
> [35380.800950] BUG: Bad page state in process qemu-kvm  pfn:dd0b6
> [35380.805825] page:ffff7fe003742d80 count:-4871 mapcount:-2126053375
> mapping:          (null) index:0x0
> [35380.815024] flags: 0x1fffc00000000000()
> [35380.818845] raw: 1fffc00000000000 0000000000000000 0000000000000000
> ffffecf981470000
> [35380.826569] raw: dead000000000100 dead000000000200 ffff8017c001c000
> 0000000000000000
> [35380.805825] page:ffff7fe003742d80 count:-4871 mapcount:-2126053375
> mapping:          (null) index:0x0
> [35380.815024] flags: 0x1fffc00000000000()
> [35380.818845] raw: 1fffc00000000000 0000000000000000 0000000000000000
> ffffecf981470000
> [35380.826569] raw: dead000000000100 dead000000000200 ffff8017c001c000
> 0000000000000000
> [35380.834294] page dumped because: nonzero _refcount
> [35380.839069] Modules linked in: vhost_net vhost tap ebtable_filter
> ebtables ip6table_filter ip6_tables iptable_filter fcoe libfcoe libfc
> 8021q garp mrp stp llc scsi_transport_fc openvswitch nf_conntrack_ipv6
> nf_nat_ipv6 nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_defrag_ipv6
> nf_nat nf_conntrack vfat fat 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_uverbs ib_umad rdma_cm
> ib_cm iw_cm mlx5_ib ib_core crc32_ce ipmi_ssif tpm_tis tpm_tis_core sg
> nfsd auth_rpcgss nfs_acl lockd grace sunrpc dm_multipath ip_tables xfs
> libcrc32c mlx5_core mlxfw devlink ahci_platform libahci_platform libahci
> qcom_emac sdhci_acpi sdhci hdma mmc_core hdma_mgmt i2c_qup dm_mirror
> dm_region_hash dm_log dm_mod
> [35380.908341] CPU: 29 PID: 18323 Comm: qemu-kvm Tainted: G W
> 4.14.15-5.hxt.aarch64 #1
> [35380.917107] Hardware name: <snip for confidential issues>
> [35380.930909] Call trace:
> [35380.933345] [<ffff000008088f00>] dump_backtrace+0x0/0x22c
> [35380.938723] [<ffff000008089150>] show_stack+0x24/0x2c
> [35380.943759] [<ffff00000893c078>] dump_stack+0x8c/0xb0
> [35380.948794] [<ffff00000820ab50>] bad_page+0xf4/0x154
> [35380.953740] [<ffff000008211ce8>] free_pages_check_bad+0x90/0x9c
> [35380.959642] [<ffff00000820c430>] free_pcppages_bulk+0x464/0x518
> [35380.965545] [<ffff00000820db98>] free_hot_cold_page+0x22c/0x300
> [35380.971448] [<ffff0000082176fc>] __put_page+0x54/0x60
> [35380.976484] [<ffff0000080b1164>] unmap_stage2_range+0x170/0x2b4
> [35380.982385] [<ffff0000080b12d8>] kvm_unmap_hva_handler+0x30/0x40
> [35380.988375] [<ffff0000080b0104>] handle_hva_to_gpa+0xb0/0xec
> [35380.994016] [<ffff0000080b2644>] kvm_unmap_hva_range+0x5c/0xd0
> [35380.999833] [<ffff0000080a8054>]
> kvm_mmu_notifier_invalidate_range_start+0x60/0xb0
> [35381.007387] [<ffff000008271f44>]
> __mmu_notifier_invalidate_range_start+0x64/0x8c
> [35381.014765] [<ffff0000082547c8>] try_to_unmap_one+0x78c/0x7a4
> [35381.020493] [<ffff000008276d04>] rmap_walk_ksm+0x124/0x1a0
> [35381.025961] [<ffff0000082551b4>] rmap_walk+0x94/0x98
> [35381.030909] [<ffff0000082555e4>] try_to_unmap+0x100/0x124
> [35381.036293] [<ffff00000828243c>] unmap_and_move+0x480/0x6fc
> [35381.041847] [<ffff000008282b6c>] migrate_pages+0x10c/0x288
> [35381.047318] [<ffff00000823c164>] compact_zone+0x238/0x954
> [35381.052697] [<ffff00000823c944>] compact_zone_order+0xc4/0xe8
> [35381.058427] [<ffff00000823d25c>] try_to_compact_pages+0x160/0x294
> [35381.064503] [<ffff00000820f074>]
> __alloc_pages_direct_compact+0x68/0x194
> [35381.071187] [<ffff000008210138>] __alloc_pages_nodemask+0xc20/0xf7c
> [35381.077437] [<ffff0000082709e4>] alloc_pages_vma+0x1a4/0x1c0
> [35381.083080] [<ffff000008285b68>]
> do_huge_pmd_anonymous_page+0x128/0x324
> [35381.089677] [<ffff000008248a24>] __handle_mm_fault+0x71c/0x7e8
> [35381.095492] [<ffff000008248be8>] handle_mm_fault+0xf8/0x194
> [35381.101049] [<ffff000008240dcc>] __get_user_pages+0x124/0x34c
> [35381.106777] [<ffff000008241870>] populate_vma_page_range+0x90/0x9c
> [35381.112941] [<ffff000008241940>] __mm_populate+0xc4/0x15c
> [35381.118322] [<ffff00000824b294>] SyS_mlockall+0x100/0x164
> [35381.123705] Exception stack(0xffff800dce5f3ec0 to 0xffff800dce5f4000)
> [35381.130128] 3ec0: 0000000000000003 d6e6024cc9b87e00 0000aaaabe94f000
> 0000000000000000
> [35381.137940] 3ee0: 0000000000000002 0000000000000000 0000000000000000
> 0000aaaacf6fc3c0
> [35381.145753] 3f00: 00000000000000e6 0000aaaacf6fc490 0000ffffeeeab0f0
> d6e6024cc9b87e00
> [35381.153565] 3f20: 0000000000000000 0000aaaabe81b3c0 0000000000000020
> 00009e53eff806b5
> [35381.161379] 3f40: 0000aaaabe94de48 0000ffffa7c269b0 0000000000000011
> 0000ffffeeeabf68
> [35381.169190] 3f60: 0000aaaaceacfe60 0000aaaabe94f000 0000aaaabe9ba358
> 0000aaaabe7ffb80
> [35381.177003] 3f80: 0000aaaabe9ba000 0000aaaabe959f64 0000000000000000
> 0000aaaabe94f000
> [35381.184815] 3fa0: 0000000000000000 0000ffffeeeabdb0 0000aaaabe5f3bf8
> 0000ffffeeeabdb0
> [35381.192628] 3fc0: 0000ffffa7c269b8 0000000060000000 0000000000000003
> 00000000000000e6
> [35381.200440] 3fe0: 0000000000000000 0000000000000000 0000000000000000
> 0000000000000000
> [35381.208254] [<ffff00000808339c>] __sys_trace_return+0x0/0x4
> [35381.213809] Disabling lock debugging due to kernel taint
> --------------------------------end--------------------------------------
> 
> The root cause might be what I fixed at [1]. But from arm kvm points of
> view, it would be better we caught the exception earlier and clearer.
> 
> If the size is not PAGE_SIZE aligned, unmap_stage2_range might unmap the
> wrong(more or less) page range. Hence it caused the "BUG: Bad page
> state"
> 
> [1] https://lkml.org/lkml/2018/5/3/1042
> 
> Signed-off-by: jia.he@hxt-semitech.com
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> v3: resend after dropping patch 2/2 of the series
> 
>  virt/kvm/arm/mmu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> index 7f6a944..8dac311 100644
> --- a/virt/kvm/arm/mmu.c
> +++ b/virt/kvm/arm/mmu.c
> @@ -297,6 +297,8 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
>  	phys_addr_t next;
>  
>  	assert_spin_locked(&kvm->mmu_lock);
> +	WARN_ON(size & ~PAGE_MASK);
> +
>  	pgd = kvm->arch.pgd + stage2_pgd_index(addr);
>  	do {
>  		/*
>