From: wanpeng li wanpengli@tencent.com
[ Upstream commit c9dfd3fb08352d439f0399b6fabe697681d2638c ]
For the duration of mapping eVMCS, it derefences ->memslots without holding ->srcu or ->slots_lock when accessing hv assist page. This patch fixes it by moving nested_sync_vmcs12_to_shadow to prepare_guest_switch, where the SRCU is already taken.
It can be reproduced by running kvm's evmcs_test selftest.
============================= warning: suspicious rcu usage 5.6.0-rc1+ #53 tainted: g w ioe ----------------------------- ./include/linux/kvm_host.h:623 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1 1 lock held by evmcs_test/8507: #0: ffff9ddd156d00d0 (&vcpu->mutex){+.+.}, at: kvm_vcpu_ioctl+0x85/0x680 [kvm]
stack backtrace: cpu: 6 pid: 8507 comm: evmcs_test tainted: g w ioe 5.6.0-rc1+ #53 hardware name: dell inc. optiplex 7040/0jctf8, bios 1.4.9 09/12/2016 call trace: dump_stack+0x68/0x9b kvm_read_guest_cached+0x11d/0x150 [kvm] kvm_hv_get_assist_page+0x33/0x40 [kvm] nested_enlightened_vmentry+0x2c/0x60 [kvm_intel] nested_vmx_handle_enlightened_vmptrld.part.52+0x32/0x1c0 [kvm_intel] nested_sync_vmcs12_to_shadow+0x439/0x680 [kvm_intel] vmx_vcpu_run+0x67a/0xe60 [kvm_intel] vcpu_enter_guest+0x35e/0x1bc0 [kvm] kvm_arch_vcpu_ioctl_run+0x40b/0x670 [kvm] kvm_vcpu_ioctl+0x370/0x680 [kvm] ksys_ioctl+0x235/0x850 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x77/0x780 entry_syscall_64_after_hwframe+0x49/0xbe
Signed-off-by: Wanpeng Li wanpengli@tencent.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kvm/vmx/vmx.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 3be65495aeb8a..a071eab3bab74 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1130,6 +1130,10 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu) vmx->guest_msrs[i].mask);
} + + if (vmx->nested.need_vmcs12_to_shadow_sync) + nested_sync_vmcs12_to_shadow(vcpu); + if (vmx->guest_state_loaded) return;
@@ -6485,8 +6489,11 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) vmcs_write32(PLE_WINDOW, vmx->ple_window); }
- if (vmx->nested.need_vmcs12_to_shadow_sync) - nested_sync_vmcs12_to_shadow(vcpu); + /* + * We did this in prepare_switch_to_guest, because it needs to + * be within srcu_read_lock. + */ + WARN_ON_ONCE(vmx->nested.need_vmcs12_to_shadow_sync);
if (test_bit(VCPU_REGS_RSP, (unsigned long *)&vcpu->arch.regs_dirty)) vmcs_writel(GUEST_RSP, vcpu->arch.regs[VCPU_REGS_RSP]);