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Subject[PATCH 4/4] KVM: nVMX: Fix using __this_cpu_read() in preemptible context
Date
From: Wanpeng Li <wanpengli@tencent.com>

BUG: using __this_cpu_read() in preemptible [00000000] code: qemu-system-x86/4590
caller is nested_vmx_enter_non_root_mode+0xebd/0x1790 [kvm_intel]
CPU: 4 PID: 4590 Comm: qemu-system-x86 Tainted: G OE 5.1.0-rc4+ #1
Call Trace:
dump_stack+0x67/0x95
__this_cpu_preempt_check+0xd2/0xe0
nested_vmx_enter_non_root_mode+0xebd/0x1790 [kvm_intel]
nested_vmx_run+0xda/0x2b0 [kvm_intel]
handle_vmlaunch+0x13/0x20 [kvm_intel]
vmx_handle_exit+0xbd/0x660 [kvm_intel]
kvm_arch_vcpu_ioctl_run+0xa2c/0x1e50 [kvm]
kvm_vcpu_ioctl+0x3ad/0x6d0 [kvm]
do_vfs_ioctl+0xa5/0x6e0
ksys_ioctl+0x6d/0x80
__x64_sys_ioctl+0x1a/0x20
do_syscall_64+0x6f/0x6c0
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Accessing per-cpu variable should disable preemption, this patch extends the
preemption disable region for __this_cpu_read().

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
arch/x86/kvm/vmx/nested.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 0c601d0..8f6f69c 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2792,14 +2792,13 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
: "cc", "memory"
);

- preempt_enable();
-
if (vmx->msr_autoload.host.nr)
vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, vmx->msr_autoload.host.nr);
if (vmx->msr_autoload.guest.nr)
vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, vmx->msr_autoload.guest.nr);

if (vm_fail) {
+ preempt_enable();
WARN_ON_ONCE(vmcs_read32(VM_INSTRUCTION_ERROR) !=
VMXERR_ENTRY_INVALID_CONTROL_FIELD);
return 1;
@@ -2811,6 +2810,7 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
local_irq_enable();
if (hw_breakpoint_active())
set_debugreg(__this_cpu_read(cpu_dr7), 7);
+ preempt_enable();

/*
* A non-failing VMEntry means we somehow entered guest mode with
--
2.7.4
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