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5c30e8101e
Skip the WRMSR fastpath in SVM's VM-Exit handler if the next RIP isn't
valid, e.g. because KVM is running with nrips=false. SVM must decode and
emulate to skip the WRMSR if the CPU doesn't provide the next RIP.
Getting the instruction bytes to decode the WRMSR requires reading guest
memory, which in turn means dereferencing memslots, and that isn't safe
because KVM doesn't hold SRCU when the fastpath runs.
Don't bother trying to enable the fastpath for this case, e.g. by doing
only the WRMSR and leaving the "skip" until later. NRIPS is supported on
all modern CPUs (KVM has considered making it mandatory), and the next
RIP will be valid the vast, vast majority of the time.
=============================
WARNING: suspicious RCU usage
6.0.0-smp--4e557fcd3d80-skip #13 Tainted: G O
-----------------------------
include/linux/kvm_host.h:954 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
1 lock held by stable/206475:
#0: ffff9d9dfebcc0f0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x8b/0x620 [kvm]
stack backtrace:
CPU: 152 PID: 206475 Comm: stable Tainted: G O 6.0.0-smp--4e557fcd3d80-skip #13
Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 10.48.0 01/27/2022
Call Trace:
<TASK>
dump_stack_lvl+0x69/0xaa
dump_stack+0x10/0x12
lockdep_rcu_suspicious+0x11e/0x130
kvm_vcpu_gfn_to_memslot+0x155/0x190 [kvm]
kvm_vcpu_gfn_to_hva_prot+0x18/0x80 [kvm]
paging64_walk_addr_generic+0x183/0x450 [kvm]
paging64_gva_to_gpa+0x63/0xd0 [kvm]
kvm_fetch_guest_virt+0x53/0xc0 [kvm]
__do_insn_fetch_bytes+0x18b/0x1c0 [kvm]
x86_decode_insn+0xf0/0xef0 [kvm]
x86_emulate_instruction+0xba/0x790 [kvm]
kvm_emulate_instruction+0x17/0x20 [kvm]
__svm_skip_emulated_instruction+0x85/0x100 [kvm_amd]
svm_skip_emulated_instruction+0x13/0x20 [kvm_amd]
handle_fastpath_set_msr_irqoff+0xae/0x180 [kvm]
svm_vcpu_run+0x4b8/0x5a0 [kvm_amd]
vcpu_enter_guest+0x16ca/0x22f0 [kvm]
kvm_arch_vcpu_ioctl_run+0x39d/0x900 [kvm]
kvm_vcpu_ioctl+0x538/0x620 [kvm]
__se_sys_ioctl+0x77/0xc0
__x64_sys_ioctl+0x1d/0x20
do_syscall_64+0x3d/0x80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.