Oliver Upton f587661f21 KVM: arm64: Don't split hugepages outside of MMU write lock ... It is possible to take a stage-2 permission fault on a page larger than PAGE_SIZE. For example, when running a guest backed by 2M HugeTLB, KVM eagerly maps at the largest possible block size. When dirty logging is enabled on a memslot, KVM does *not* eagerly split these 2M stage-2 mappings and instead clears the write bit on the pte. Since dirty logging is always performed at PAGE_SIZE granularity, KVM lazily splits these 2M block mappings down to PAGE_SIZE in the stage-2 fault handler. This operation must be done under the write lock. Since commit f783ef1c0e ("KVM: arm64: Add fast path to handle permission relaxation during dirty logging"), the stage-2 fault handler conditionally takes the read lock on permission faults with dirty logging enabled. To that end, it is possible to split a 2M block mapping while only holding the read lock. The problem is demonstrated by running kvm_page_table_test with 2M anonymous HugeTLB, which splats like so: WARNING: CPU: 5 PID: 15276 at arch/arm64/kvm/hyp/pgtable.c:153 stage2_map_walk_leaf+0x124/0x158 [...] Call trace: stage2_map_walk_leaf+0x124/0x158 stage2_map_walker+0x5c/0xf0 __kvm_pgtable_walk+0x100/0x1d4 __kvm_pgtable_walk+0x140/0x1d4 __kvm_pgtable_walk+0x140/0x1d4 kvm_pgtable_walk+0xa0/0xf8 kvm_pgtable_stage2_map+0x15c/0x198 user_mem_abort+0x56c/0x838 kvm_handle_guest_abort+0x1fc/0x2a4 handle_exit+0xa4/0x120 kvm_arch_vcpu_ioctl_run+0x200/0x448 kvm_vcpu_ioctl+0x588/0x664 __arm64_sys_ioctl+0x9c/0xd4 invoke_syscall+0x4c/0x144 el0_svc_common+0xc4/0x190 do_el0_svc+0x30/0x8c el0_svc+0x28/0xcc el0t_64_sync_handler+0x84/0xe4 el0t_64_sync+0x1a4/0x1a8 Fix the issue by only acquiring the read lock if the guest faulted on a PAGE_SIZE granule w/ dirty logging enabled. Add a WARN to catch locking bugs in future changes. Fixes: f783ef1c0e ("KVM: arm64: Add fast path to handle permission relaxation during dirty logging") Cc: Jing Zhang <jingzhangos@google.com> Signed-off-by: Oliver Upton <oupton@google.com> Reviewed-by: Reiji Watanabe <reijiw@google.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20220401194652.950240-1-oupton@google.com		2022-04-06 10:41:05 +01:00
..
boot	SoC: fixes for 5.18, part 1	2022-04-01 13:21:19 -07:00
configs	ARM: DT updates for 5.18	2022-03-23 18:37:22 -07:00
crypto	crypto: arm64 - cleanup comments	2022-03-09 15:12:32 +12:00
hyperv	arm64: hyperv: Initialize hypervisor on boot	2021-08-04 16:54:36 +00:00
include	Char/Misc and other driver updates for 5.18-rc1	2022-03-28 12:27:35 -07:00
kernel	ptrace: Cleanups for v5.18	2022-03-28 17:29:53 -07:00
kvm	KVM: arm64: Don't split hugepages outside of MMU write lock	2022-04-06 10:41:05 +01:00
lib	Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6	2022-03-21 16:02:36 -07:00
mm	kasan, arm64: don't tag executable vmalloc allocations	2022-03-24 19:06:48 -07:00
net	kasan, arm64: don't tag executable vmalloc allocations	2022-03-24 19:06:48 -07:00
tools	Merge branch 'for-next/spectre-bhb' into for-next/core	2022-03-14 19:08:31 +00:00
xen	xen: allow pv-only hypercalls only with CONFIG_XEN_PV	2021-11-02 08:11:01 -05:00
Kbuild	kbuild: use more subdir- for visiting subdirectories while cleaning	2021-10-24 13:49:46 +09:00
Kconfig	Char/Misc and other driver updates for 5.18-rc1	2022-03-28 12:27:35 -07:00
Kconfig.debug
Kconfig.platforms	ARM: DT updates for 5.18	2022-03-23 18:37:22 -07:00
Makefile	arm64/xor: use EOR3 instructions when available	2021-12-14 12:14:26 +00:00