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SubjectRe: [PATCH V2 1/2] KVM/VMX: Check ept_pointer before flushing ept tlb
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On 06/12/18 08:34, lantianyu1986@gmail.com wrote:
> From: Lan Tianyu <Tianyu.Lan@microsoft.com>
>
> This patch is to initialize ept_pointer to INVALID_PAGE and check it
> before flushing ept tlb. If ept_pointer is invalid, bypass the flush
> request.
>
> Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>

Can you explain better *why* this patch is needed? Also, should
vmx->ept_pointer be cleared at reset time, rather than vCPU creation?

Thanks,

Paolo

> ---
> arch/x86/kvm/vmx.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index c379d0bfdcba..6577ec8cbb0f 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1582,11 +1582,18 @@ static int vmx_hv_remote_flush_tlb(struct kvm *kvm)
> /*
> * FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs the address of the
> * base of EPT PML4 table, strip off EPT configuration information.
> + * If ept_pointer is invalid pointer, bypass the flush request.
> */
> if (to_kvm_vmx(kvm)->ept_pointers_match != EPT_POINTERS_MATCH) {
> - kvm_for_each_vcpu(i, vcpu, kvm)
> + kvm_for_each_vcpu(i, vcpu, kvm) {
> + u64 ept_pointer = to_vmx(vcpu)->ept_pointer;
> +
> + if (!VALID_PAGE(ept_pointer))
> + continue;
> +
> ret |= hyperv_flush_guest_mapping(
> - to_vmx(kvm_get_vcpu(kvm, i))->ept_pointer & PAGE_MASK);
> + ept_pointer & PAGE_MASK);
> + }
> } else {
> ret = hyperv_flush_guest_mapping(
> to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer & PAGE_MASK);
> @@ -11614,6 +11621,8 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
> vmx->pi_desc.nv = POSTED_INTR_VECTOR;
> vmx->pi_desc.sn = 1;
>
> + vmx->ept_pointer = INVALID_PAGE;
> +
> return &vmx->vcpu;
>
> free_vmcs:
>

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