Haozhong Zhang <haozhong.zh...@intel.com> writes:
> This patch removes the vpid check when emulating nested invvpid
> instruction of type all-contexts invalidation. The existing code is
> incorrect because:
> (1) According to Intel SDM Vol 3, Section "INVVPID - Invalidate
> Translations Based on VPID", invvpid instruction does not check
> vpid in the invvpid descriptor when its type is all-contexts
> invalidation.
But iirc isn't vpid=0 reserved for root mode ? I think we don't want
L1 hypervisor to be able do a invvpid(0).
> (2) According to the same document, invvpid of type all-contexts
> invalidation does not require there is an active VMCS, so/and
> get_vmcs12() in the existing code may result in a NULL-pointer
> dereference. In practice, it can crash both KVM itself and L1
> hypervisors that use invvpid (e.g. Xen).
If that is the case, then just check if it's null and return without
doing anything.
> Signed-off-by: Haozhong Zhang <haozhong.zh...@intel.com>
> ---
> arch/x86/kvm/vmx.c | 5 -----
> 1 file changed, 5 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 87acc52..af823a3 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -7394,11 +7394,6 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
>
> switch (type) {
> case VMX_VPID_EXTENT_ALL_CONTEXT:
> - if (get_vmcs12(vcpu)->virtual_processor_id == 0) {
> - nested_vmx_failValid(vcpu,
> - VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
> - return 1;
> - }
> __vmx_flush_tlb(vcpu, to_vmx(vcpu)->nested.vpid02);
> nested_vmx_succeed(vcpu);
> break;
I also noticed a BUG() here in the default. It might be a good idea to replace
it with a WARN.
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