On Wed, Apr 17, 2013 at 08:07:40PM +0300, Abel Gordon wrote:
> Allocate a shadow vmcs used by the processor to shadow part of the fields
> stored in the software defined VMCS12 (let L1 access fields without causing
> exits). Note we keep a shadow vmcs only for the current vmcs12. Once a vmcs12
> becomes non-current, its shadow vmcs is released.
>
>
> Signed-off-by: Abel Gordon <abelg@xxxxxxxxxx>
> ---
> arch/x86/kvm/vmx.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> --- .before/arch/x86/kvm/vmx.c 2013-04-17 19:58:32.000000000 +0300
> +++ .after/arch/x86/kvm/vmx.c 2013-04-17 19:58:32.000000000 +0300
> @@ -355,6 +355,7 @@ struct nested_vmx {
> /* The host-usable pointer to the above */
> struct page *current_vmcs12_page;
> struct vmcs12 *current_vmcs12;
> + struct vmcs *current_shadow_vmcs;
>
> /* vmcs02_list cache of VMCSs recently used to run L2 guests */
> struct list_head vmcs02_pool;
> @@ -5517,6 +5518,7 @@ static int handle_vmon(struct kvm_vcpu *
> {
> struct kvm_segment cs;
> struct vcpu_vmx *vmx = to_vmx(vcpu);
> + struct vmcs *shadow_vmcs;
>
> /* The Intel VMX Instruction Reference lists a bunch of bits that
> * are prerequisite to running VMXON, most notably cr4.VMXE must be
> @@ -5540,6 +5542,16 @@ static int handle_vmon(struct kvm_vcpu *
> kvm_inject_gp(vcpu, 0);
> return 1;
> }
> + if (enable_shadow_vmcs) {
> + shadow_vmcs = alloc_vmcs();
> + if (!shadow_vmcs)
> + return -ENOMEM;
> + /* mark vmcs as shadow */
> + shadow_vmcs->revision_id |= (1u << 31);
> + /* init shadow vmcs */
> + vmcs_clear(shadow_vmcs);
> + vmx->nested.current_shadow_vmcs = shadow_vmcs;
> + }
>
Guest can ddos host by calling vmxon repeatedly causing host to leak
memory. This point to a bug in vmxon implementation. vmxon should call
nested_vmx_failInvalid() if (vmx->nested.vmxon).
> INIT_LIST_HEAD(&(vmx->nested.vmcs02_pool));
> vmx->nested.vmcs02_num = 0;
>
> --
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--
Gleb.
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