Re: [PATCH] KVM: nVMX: initialize PML fields in vmcs02

[David Hildenbrand <david@redhat.com>]

On 04.04.2017 14:18, Ladi Prosek wrote:
> L2 was running with uninitialized PML fields which led to incomplete
> dirty bitmap logging. This manifested as all kinds of subtle erratic
> behavior of the nested guest.
> 
> Fixes: 843e4330573c ("KVM: VMX: Add PML support in VMX")
> Signed-off-by: Ladi Prosek <lprosek@redhat.com>
> ---
>  arch/x86/kvm/vmx.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 2ee00db..f47d701 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -10267,6 +10267,18 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
>  
>  	}
>  
> +	if (enable_pml) {
> +		/*
> +		 * Conceptually we want to copy the PML address and index from
> +		 * vmcs01 here, and then back to vmcs01 on nested vmexit. But,
> +		 * since we always flush the log on each vmexit, this happens

we == KVM running in g2?

If so, other hypervisors might handle this differently.

> +		 * to be equivalent to simply resetting the fields in vmcs02.
> +		 */
> +		ASSERT(vmx->pml_pg);
> +		vmcs_write64(PML_ADDRESS, page_to_phys(vmx->pml_pg));
> +		vmcs_write16(GUEST_PML_INDEX, PML_ENTITY_NUM - 1);
> +	}
> +
>  	if (nested_cpu_has_ept(vmcs12)) {
>  		kvm_mmu_unload(vcpu);
>  		nested_ept_init_mmu_context(vcpu);
> 


-- 

Thanks,

David