* [Question] Intercept CR3 access in EPT
@ 2012-10-08 8:15 R
2012-10-08 19:37 ` Marcelo Tosatti
0 siblings, 1 reply; 3+ messages in thread
From: R @ 2012-10-08 8:15 UTC (permalink / raw)
To: kvm
Hi,
I am a student. And my teacher told me to monitor every process in guest.
So, I try to intercept every Cr3 access. However, if kvm is loaded
with EPT enable, Acesses to Cr3 would not cause VM-exit.
I modified the code to change vmcs configuration.
To be specific, these functions are rewirted.
static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
unsigned long cr0,
struct kvm_vcpu *vcpu)
{
....
} else if (!is_paging(vcpu)) {
/* From nonpaging to paging */
vmcs_write32(CPU_BASED_VM_EXEC_CONTROL,
vmcs_read32(CPU_BASED_VM_EXEC_CONTROL) &
- ~(CPU_BASED_CR3_LOAD_EXITING |
+ ~( // CPU_BASED_CR3_LOAD_EXITING|
CPU_BASED_CR3_STORE_EXITING));
....
}
static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
{
...
if (_cpu_based_2nd_exec_control & SECONDARY_EXEC_ENABLE_EPT) {
/* CR3 accesses and invlpg don't need to cause VM Exits when EPT
enabled */
- _cpu_based_exec_control &= ~(CPU_BASED_CR3_LOAD_EXITING |
+ _cpu_based_exec_control &= ~( //
CPU_BASED_CR3_LOAD_EXITING |
CPU_BASED_CR3_STORE_EXITING |
CPU_BASED_INVLPG_EXITING);
....
}
I though it can force every Cr3 access to be trapped with EPT enable.
However, VM seems to fail to boot when it changes from nonpaging to
paging.
Do U guys have any idea? Or Can someone tell me how can I intercept
Cr3 access and why can not it work?
Thank U for answering.
--
Thanks
Rui Wu
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [Question] Intercept CR3 access in EPT
2012-10-08 8:15 [Question] Intercept CR3 access in EPT R
@ 2012-10-08 19:37 ` Marcelo Tosatti
2012-10-09 1:21 ` R
0 siblings, 1 reply; 3+ messages in thread
From: Marcelo Tosatti @ 2012-10-08 19:37 UTC (permalink / raw)
To: R; +Cc: kvm
On Mon, Oct 08, 2012 at 04:15:57PM +0800, R wrote:
> Hi,
>
> I am a student. And my teacher told me to monitor every process in guest.
> So, I try to intercept every Cr3 access. However, if kvm is loaded
> with EPT enable, Acesses to Cr3 would not cause VM-exit.
Disable EPT by loading kvm-intel.ko module with enable_ept=0 parameter.
Then, CR3 accesses will trap.
> I modified the code to change vmcs configuration.
> To be specific, these functions are rewirted.
> static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
> unsigned long cr0,
> struct kvm_vcpu *vcpu)
> {
> ....
> } else if (!is_paging(vcpu)) {
> /* From nonpaging to paging */
> vmcs_write32(CPU_BASED_VM_EXEC_CONTROL,
> vmcs_read32(CPU_BASED_VM_EXEC_CONTROL) &
> - ~(CPU_BASED_CR3_LOAD_EXITING |
> + ~( // CPU_BASED_CR3_LOAD_EXITING|
> CPU_BASED_CR3_STORE_EXITING));
> ....
> }
>
> static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
> {
> ...
> if (_cpu_based_2nd_exec_control & SECONDARY_EXEC_ENABLE_EPT) {
> /* CR3 accesses and invlpg don't need to cause VM Exits when EPT
> enabled */
> - _cpu_based_exec_control &= ~(CPU_BASED_CR3_LOAD_EXITING |
> + _cpu_based_exec_control &= ~( //
> CPU_BASED_CR3_LOAD_EXITING |
> CPU_BASED_CR3_STORE_EXITING |
> CPU_BASED_INVLPG_EXITING);
> ....
> }
>
> I though it can force every Cr3 access to be trapped with EPT enable.
> However, VM seems to fail to boot when it changes from nonpaging to
> paging.
> Do U guys have any idea? Or Can someone tell me how can I intercept
> Cr3 access and why can not it work?
>
> Thank U for answering.
>
> --
> Thanks
> Rui Wu
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [Question] Intercept CR3 access in EPT
2012-10-08 19:37 ` Marcelo Tosatti
@ 2012-10-09 1:21 ` R
0 siblings, 0 replies; 3+ messages in thread
From: R @ 2012-10-09 1:21 UTC (permalink / raw)
To: Marcelo Tosatti; +Cc: kvm
Hi,
Actually, I know that disabling EPT would work. But thank U anyway.
What I interesting in is why would it fail when EPT is enable.
Thank U for answering.
2012/10/9 Marcelo Tosatti <mtosatti@redhat.com>:
> On Mon, Oct 08, 2012 at 04:15:57PM +0800, R wrote:
>> Hi,
>>
>> I am a student. And my teacher told me to monitor every process in guest.
>> So, I try to intercept every Cr3 access. However, if kvm is loaded
>> with EPT enable, Acesses to Cr3 would not cause VM-exit.
>
> Disable EPT by loading kvm-intel.ko module with enable_ept=0 parameter.
> Then, CR3 accesses will trap.
>
>> I modified the code to change vmcs configuration.
>> To be specific, these functions are rewirted.
>> static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
>> unsigned long cr0,
>> struct kvm_vcpu *vcpu)
>> {
>> ....
>> } else if (!is_paging(vcpu)) {
>> /* From nonpaging to paging */
>> vmcs_write32(CPU_BASED_VM_EXEC_CONTROL,
>> vmcs_read32(CPU_BASED_VM_EXEC_CONTROL) &
>> - ~(CPU_BASED_CR3_LOAD_EXITING |
>> + ~( // CPU_BASED_CR3_LOAD_EXITING|
>> CPU_BASED_CR3_STORE_EXITING));
>> ....
>> }
>>
>> static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
>> {
>> ...
>> if (_cpu_based_2nd_exec_control & SECONDARY_EXEC_ENABLE_EPT) {
>> /* CR3 accesses and invlpg don't need to cause VM Exits when EPT
>> enabled */
>> - _cpu_based_exec_control &= ~(CPU_BASED_CR3_LOAD_EXITING |
>> + _cpu_based_exec_control &= ~( //
>> CPU_BASED_CR3_LOAD_EXITING |
>> CPU_BASED_CR3_STORE_EXITING |
>> CPU_BASED_INVLPG_EXITING);
>> ....
>> }
>>
>> I though it can force every Cr3 access to be trapped with EPT enable.
>> However, VM seems to fail to boot when it changes from nonpaging to
>> paging.
>> Do U guys have any idea? Or Can someone tell me how can I intercept
>> Cr3 access and why can not it work?
>>
>> Thank U for answering.
>
>>
>> --
>> Thanks
>> Rui Wu
>> --
>> To unsubscribe from this list: send the line "unsubscribe kvm" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Thanks
Rui Wu
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-10-08 8:15 [Question] Intercept CR3 access in EPT R
2012-10-08 19:37 ` Marcelo Tosatti
2012-10-09 1:21 ` R
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