On 11/5/2019 6:41 PM, Paolo Bonzini wrote:
On 05/11/19 10:20, Chenyi Qiang wrote:
The three msr number lists(msrs_to_save[], emulated_msrs[] and
msr_based_features[]) are global arrays of kvm.ko, which are
initialized/adjusted (copy supported MSRs forward to override the
unsupported MSRs) when installing kvm-{intel,amd}.ko, but it doesn't
reset these three arrays to their initial value when uninstalling
kvm-{intel,amd}.ko. Thus, at the next installation, kvm-{intel,amd}.ko
will initialize the modified arrays with some MSRs lost and some MSRs
duplicated.
So allocate and initialize these three MSR number lists dynamically when
installing kvm-{intel,amd}.ko and free them when uninstalling.
I don't understand. Do you mean insmod/rmmod when you say
installing/uninstalling? Global data must be reloaded from the ELF file
when insmod is executed.
Yes, we mean insmod/rmmod.
The problem is that these three MSR arrays belong to kvm.ko but not
kvm-{intel,amd}.ko. When we rmmod kvm_intel.ko, it does nothing to them.
How is the bug reproducible?
Suppose there is an intel machine.
1. You can first run
#rmmod kvm-intel.ko
#insmod kvm-intel.ko nested=0
2. and then
#rmmod kvm-intel.ko
#insmod kvm-intel.ko nested=1
In step 1, all the vmx-related MSRs in msr_based_features[] are not
supported due to nested=0. And it will move MSR_IA32_UCODE_REV and
MSR_IA32_ARCH_CAPABILITIES (on my Cascadelake server) forward to
override array member 0 and 1 (MSR_IA32_VMX_BASIC and
MSR_IA32_VMX_TRUE_PINBASED_CTLS).
In step 2, we just lose MSR_IA32_VMX_BASIC and
MSR_IA32_VMX_TRUE_PINBASED_CTLS of VMX and get duplicated
MSR_IA32_UCODE_REV and MSR_IA32_ARCH_CAPABILITIES.
Paolo
