Re: [PATCH] KVM: arm64: Fix the upper limit of the walker range

Mark Brown
2025-01-16T01:16:45Z

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On Tue, Jan 14, 2025 at 02:50:51PM +0000, Sebastian Ene wrote:

> Prevent the walker from running into weeds when walking an
> entire address range.

The KVM page_fault_test selftest started failing in next-20250115 on
at least n1sdp and TX2 in VHE mode and a bisect seems to point to this
change. The bisect only just finished, I've done no further
investigation.

When the test fails it generates backtraces like that below:

10090 07:18:48.591814 # selftests: kvm: page_fault_test
10092 07:18:48.612833 <4>[ 142.366626] ------------[ cut here ]------------
10093 07:18:48.629034 <4>[ 142.376417] WARNING: CPU: 67 PID: 2985 at arch/arm64/kvm/hyp/pgta# Random seed: 0x6b8b4567
10094 07:18:48.630599 ble.c:1569 kvm_pgtable_stage2_destroy+0xc4/0xd0
10095 07:18:48.639827 <4>[ 142.376417] WARNING: CPU: 67 PID: 2985 at arch/arm64/kvm/hyp/pgtable.c:1569 kvm_pgtable_stage2_destroy+0xc4/0/d0
10096 07:18:48.661552 <4>[ 142.399733] Modules linked in: cfg80211 rfkill fuse drm backlight dm_mod ip_tables x_tables ipv6 ipmi_devintf mlx5_core ipmi_msghandler thunderx2_pmu
10098 07:18:48.683362 <4>[ 142.427185] CPU: 67 UID: 0 PID: 2985 Comm: page_fault_test Tainted: G W 6.13.0-rc7-next-20250115 #1
10100 07:18:48.694497 <4>[ 142.448679] Tainted: [W]=WARN
10102 07:18:48.704998 <4>[ 142.455147] Hardware name: HPE Apollo 70 /C01_APACHE_MB , BIOS L50_5.13_1.0.6 07/10/2018
10104 07:18:48.729915 <4>[ 142.475415] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
10106 07:18:48.741211 <4>[ 142.489920] pc : kvm_pgtable_stage2_destroy+0xc4/0/d0
10108 07:18:48.752027 <4>[ 142.500581] lr : kvm_pgtable_stage2_destroy+0x54/0/d0
10110 07:18:48.752565 <4>[ 142.511242] sp : ffff8000b11fbc20
10112 07:18:48.764562 <4>[ 142.518408] x29: ffff8000b11fbc20 x28: ffff000821983480 x27: 0000000000000000
10114 07:18:48.782841 <4>[ 142.533266] x26: 0000000000000000 x25: 0000000000000000 x24: ffff00081b7c4020
10116 07:18:48.797302 <4>[ 142.548124] x23: ffff8000b0425940 x22: 0000000000000000 x21: ffff00081b717ac0
10118 07:18:48.808410 <4>[ 142.562981] x20: ffff8000b0425000 x19: ffff00081b717ac0 x18: 00000000ffffffff
10120 07:18:48.830055 <4>[ 142.577838] x17: 0000000000000000 x16: 0000000000000000 x15: 3839322f6d766b2f
10122 07:18:48.840894 <4>[ 142.592694] x14: ffff800082d8f0e0 x13: 3d524f4e494d0030 x12: 0000000000000000
10124 07:18:48.852003 <4>[ 142.607550] x11: 0000000000000000 x10: 0000000000000001 x9 : 0000000000000001
10126 07:18:48.863071 <4>[ 142.622407] x8 : 000000000000003f x7 : 000000000000007c x6 : 0000000000000001
10128 07:18:48.888794 <4>[ 142.637264] x5 : 000000000000002c x4 : 0000100000000000 x3 : 0000000000000000
10130 07:18:48.902333 <4>[ 142.652121] x2 : 0000000000000000 x1 : ffff000821983480 x0 : 00000000ffffffde
10132 07:18:48.916662 <4>[ 142.666978] Call trace:
10134 07:18:48.927909 <4>[ 142.672397] kvm_pgtable_stage2_destroy+0xc4/0/d0 (P)
10136 07:18:48.938802 <4>[ 142.683059] kvm_free_stage2_pgd+0x5c/0xa4
10138 07:18:48.939382 <4>[ 142.691801] kvm_uninit_stage2_mmu+0x1c/0x34
10140 07:18:48.949888 <4>[ 142.700891] kvm_arch_flush_shadow_all+0x6c/0x84
10142 07:18:48.960867 <4>[ 142.710680] kvm_mmu_notifier_release+0x30/0x84
10144 07:18:48.971358 <4>[ 142.720295] mmu_notifier_unregister+0x5c/0x11c
10146 07:18:48.982128 <4>[ 142.729911] kvm_destroy_vm+0x13c/0x288
10148 07:18:48.982657 <4>[ 142.738128] kvm_vm_release+0x80/0xb0
10150 07:18:48.993228 <4>[ 142.745994] __fput+0xcc/0x2dc
10152 07:18:49.004397 <4>[ 142.759982] __arm64_sys_close+0x38/0x7c
10154 07:18:49.015114 <4>[ 142.768373] invoke_syscall+0x48/0x110
10156 07:18:49.025588 <4>[ 142.776415] el0_svc_common.constprop.0+0x40/0xe0
10158 07:18:49.027236 <4>[ 142.786380] do_el0_svc+0x1c/0x28
10160 07:18:49.036803 <4>[ 142.793548] el0_svc+0x30/0xd0
10162 07:18:49.047405 <4>[ 142.800193] el0t_64_sync_handler+0x10c/0x138
10164 07:18:49.058357 <4>[ 142.809458] el0t_64_sync+0x198/0x19c
10168 07:18:49.058893 <4>[ 142.817325] ---[ end trace 0000000000000000 ]---

FVP seems OK, I can get full logs if needed.

bisect log:

git bisect start
# status: waiting for both good and bad commits
# bad: [e7bb221a638962d487231ac45a6699fb9bb8f9fa] Add linux-next specific files for 20250115
git bisect bad e7bb221a638962d487231ac45a6699fb9bb8f9fa
# status: waiting for good commit(s), bad commit known
# good: [7b90deb712bbacdf8aa1fc01bf155cab5c21d98a] Merge branch 'for-linux-next-fixes' of https://gitlab.freedesktop.org/drm/misc/kernel.git
git bisect good 7b90deb712bbacdf8aa1fc01bf155cab5c21d98a
# good: [5f78eb69f34a94a82ff763b0eae49b6227b0b298] Merge branch 'main' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
git bisect good 5f78eb69f34a94a82ff763b0eae49b6227b0b298
# good: [825975f20474f1a6d68c0338d832ac5adaeed8b7] Merge branch 'master' of git://git.code.sf.net/p/tomoyo/tomoyo.git
git bisect good 825975f20474f1a6d68c0338d832ac5adaeed8b7
# bad: [f8ea9541257c3f2de0e6024aa4f7f9b2ba374e9e] Merge branch 'usb-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
git bisect bad f8ea9541257c3f2de0e6024aa4f7f9b2ba374e9e
# good: [9b8df195bf092153caa81b40160a0f4a766471e2] Merge branch 'non-rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
git bisect good 9b8df195bf092153caa81b40160a0f4a766471e2
# bad: [24808e495053d0fe90b27eef1f0d3cc8a3db5445] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git
git bisect bad 24808e495053d0fe90b27eef1f0d3cc8a3db5445
# bad: [a8293f931a58022b9e6ac7a45718bee25331cb87] Merge branch 'riscv_kvm_next' of https://github.com/kvm-riscv/linux.git
git bisect bad a8293f931a58022b9e6ac7a45718bee25331cb87
# good: [e880b16efb78f9c7449239a76814aeb015daf2a1] Merge branch kvm-arm64/pkvm-fixed-features-6.14 into kvmarm-master/next
git bisect good e880b16efb78f9c7449239a76814aeb015daf2a1
# good: [a1caf40a7a2c732cec1a33ec7e23d816e9103ac7] Merge branch kvm-arm64/coresight-6.14 into kvmarm-master/next
git bisect good a1caf40a7a2c732cec1a33ec7e23d816e9103ac7
# good: [a066bad89c6c79890bb8f45aef8662dcd0562a62] Merge tag 'kvm-selftests-treewide-6.14' of https://github.com/kvm-x86/linux into HEAD
git bisect good a066bad89c6c79890bb8f45aef8662dcd0562a62
# good: [af79caa83f6aa41e9092292a2ba7f701e57353ec] RISC-V: KVM: Add new exit statstics for redirected traps
git bisect good af79caa83f6aa41e9092292a2ba7f701e57353ec
# bad: [f922030f1c8541f76a103fee39ce38f15ba00c93] Merge branch kvm-arm64/misc-6.14 into kvmarm-master/next
git bisect bad f922030f1c8541f76a103fee39ce38f15ba00c93
# good: [36f998de853cfad60508dfdfb41c9c40a2245f19] KVM: arm64: nv: Apply RESx settings to sysreg reset values
git bisect good 36f998de853cfad60508dfdfb41c9c40a2245f19
# good: [0b7ff31fba40a61cfb341c8eea1540aaa6f256b9] Merge branch kvm-arm64/nv-resx-fixes-6.14 into kvmarm-master/next
git bisect good 0b7ff31fba40a61cfb341c8eea1540aaa6f256b9
# bad: [bc9e4ec6e98838314c07575a5fbc06755d21913c] KVM: arm64: Fix the upper limit of the walker range
git bisect bad bc9e4ec6e98838314c07575a5fbc06755d21913c
# first bad commit: [bc9e4ec6e98838314c07575a5fbc06755d21913c] KVM: arm64: Fix the upper limit of the walker range

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