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Marek reported a BUG resulting from the recent parallel faults changes,
as the hyp stage-1 map walker attempted to allocate table memory while
holding the RCU read lock:
BUG: sleeping function called from invalid context at
include/linux/sched/mm.h:274
in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper/0
preempt_count: 0, expected: 0
RCU nest depth: 1, expected: 0
2 locks held by swapper/0/1:
#0: ffff80000a8a44d0 (kvm_hyp_pgd_mutex){+.+.}-{3:3}, at:
__create_hyp_mappings+0x80/0xc4
#1: ffff80000a927720 (rcu_read_lock){....}-{1:2}, at:
kvm_pgtable_walk+0x0/0x1f4
CPU: 2 PID: 1 Comm: swapper/0 Not tainted 6.1.0-rc3+ #5918
Hardware name: Raspberry Pi 3 Model B (DT)
Call trace:
dump_backtrace.part.0+0xe4/0xf0
show_stack+0x18/0x40
dump_stack_lvl+0x8c/0xb8
dump_stack+0x18/0x34
__might_resched+0x178/0x220
__might_sleep+0x48/0xa0
prepare_alloc_pages+0x178/0x1a0
__alloc_pages+0x9c/0x109c
alloc_page_interleave+0x1c/0xc4
alloc_pages+0xec/0x160
get_zeroed_page+0x1c/0x44
kvm_hyp_zalloc_page+0x14/0x20
hyp_map_walker+0xd4/0x134
kvm_pgtable_visitor_cb.isra.0+0x38/0x5c
__kvm_pgtable_walk+0x1a4/0x220
kvm_pgtable_walk+0x104/0x1f4
kvm_pgtable_hyp_map+0x80/0xc4
__create_hyp_mappings+0x9c/0xc4
kvm_mmu_init+0x144/0x1cc
kvm_arch_init+0xe4/0xef4
kvm_init+0x3c/0x3d0
arm_init+0x20/0x30
do_one_initcall+0x74/0x400
kernel_init_freeable+0x2e0/0x350
kernel_init+0x24/0x130
ret_from_fork+0x10/0x20
Since the hyp stage-1 table walkers are serialized by kvm_hyp_pgd_mutex,
RCU protection really doesn't add anything. Don't acquire the RCU read
lock for an exclusive walk.
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221118182222.3932898-3-oliver.upton@linux.dev
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.