Hello, I tried to write a piece of code to
start vmx.
This code is directly interacting with cpu
instead of with virtual cpu as in xen.
But every time I call vmxon, a GP exception
happens.
Could anybody help me on this? The
following is the context
- After booting up to the
program, I disable A20M.
- allocate a 4kb-aligned
vmxon region and calculate its physical address.
- setup identity page
table and enter protected page mode. In this step I also set x86_cr0_ne ( cr0.bit5)
- call start_vmx. This
start_vmx function is similar to the one in xen3.1.0
- test cpuid with eax
= 1. ecx.vmxe(bit5) is 1.
- Test IA32_FEATURE_CONTROL_MSR,
result is 0x05, so bit 0 and bit 2 are both 1.
- Set cr4.vmxe (bit13)
to 1
- Call vmx_init_vmcs_config().
This function is the same as in xen3.1.0.
- Call vmxon, passing
it the physical adderss calculated in step2, using the same op-code as
xen
f. stop
vmx by calling vmxoff.
Using “while(1)”, I traced and
found the GP exception happened in step 4.e.
From Intel Software Development Manual 2B,
I get the following conditions to throw a GP.
IF (CPL >
0) or (in A20M mode) or
(the values of
CR0 and CR4 are supported in VMX operation) or
(bit 0 (lock
bit) of IA32_FEATURE_CONTROL MSR is clear) or
(bit 2 of
IA32_FEATURE_CONTROL MSR is clear)
THEN #GP(0);
I checked the conditions and found none of
them was violated.
The results are as follows
CR0 : 0x80000031
IA32_VMX_CR0_FIXED0: 0x80000021
IA32_VMX_CR0_FIXED1: 0xFFFFFFFF
CR4 : 0x2250
IA32_VMX_CR4_FIXED0: 0x2000
IA32_VMX_CR4_FIXED1: 0x27FF
IA32_VMX_BASIC_MSR is 001A 0400 0000 0007
The revision ID 0x07 is assigned to the
corresponding field in vmxon region in the step 4.d
IA32_FEATURE_CONTROL is 0x05
My PC has a 32 bit, VT-support multi-core CPU.
I use only the BSP and haven’t dealt
with multi-cpu wake-up.
Best
regards,
Hu Jia
Yi
Ext:
20430
Tel:
65-67510430
