[PATCH] KVM: nVMX: Fix L2 guest crash when VPID is disabled on L0

[Wanpeng Li <kernellwp@gmail.com>]

From: Wanpeng Li <wanpeng.li@hotmail.com>

L2 guest crash during boot if VPID is enabled on L1 and disabled on L0. This 
also can be catched by kvm-unit-tests/vmx.flat when VPID is disabled on L0.

KVM: entry failed, hardware error 0x7
EAX=00000000 EBX=00000000 ECX=00000000 EDX=000306c3
ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
EIP=0000fff0 EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 00000000 0000ffff 00009300
CS =f000 ffff0000 0000ffff 00009b00
SS =0000 00000000 0000ffff 00009300
DS =0000 00000000 0000ffff 00009300
FS =0000 00000000 0000ffff 00009300
GS =0000 00000000 0000ffff 00009300
LDT=0000 00000000 0000ffff 00008200
TR =0000 00000000 0000ffff 00008b00
GDT=     00000000 0000ffff
IDT=     00000000 0000ffff
CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000 
DR6=00000000ffff0ff0 DR7=0000000000000400
EFER=0000000000000000

The enable_vpid sysfs perm parameter miss the 0 prefix, so the enable_vpid 
is failed to be disabled though vmcs_config bit is not set. This patch fixes 
it by utilizing S_IRUGO which includes 0 prefix instead.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
 arch/x86/kvm/vmx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 98e82ee..a7e4880 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -66,7 +66,7 @@ static const struct x86_cpu_id vmx_cpu_id[] = {
 MODULE_DEVICE_TABLE(x86cpu, vmx_cpu_id);
 
 static bool __read_mostly enable_vpid = 1;
-module_param_named(vpid, enable_vpid, bool, 0444);
+module_param_named(vpid, enable_vpid, bool, S_IRUGO);
 
 static bool __read_mostly flexpriority_enabled = 1;
 module_param_named(flexpriority, flexpriority_enabled, bool, S_IRUGO);
-- 
2.7.4