Re: [PATCH] KVM: nVMX: Update VMCS02 when L2 PAE PDPTE updates detected

[Sean Christopherson <sean.j.christopherson@xxxxxxxxx>]

On Mon, Aug 17, 2020 at 05:43:14PM -0700, Peter Shier wrote:
> ---
>  arch/x86/include/asm/kvm_host.h |  1 +
>  arch/x86/kvm/vmx/vmx.c          | 11 +++++++++++
>  arch/x86/kvm/x86.c              |  2 ++
>  3 files changed, 14 insertions(+)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 5ab3af7275d8..c9971c5d316f 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1227,6 +1227,7 @@ struct kvm_x86_ops {
>  	int (*enable_direct_tlbflush)(struct kvm_vcpu *vcpu);
>  
>  	void (*migrate_timers)(struct kvm_vcpu *vcpu);
> +	void (*load_pdptrs)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu);
>  };
>  
>  struct kvm_x86_nested_ops {
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 46ba2e03a892..b8e36ea077dc 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2971,6 +2971,16 @@ static void vmx_flush_tlb_guest(struct kvm_vcpu *vcpu)
>  	vpid_sync_context(to_vmx(vcpu)->vpid);
>  }
>  
> +static void vmx_load_pdptrs(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
> +{
> +	if (enable_ept && is_guest_mode(vcpu)) {
> +		vmcs_write64(GUEST_PDPTR0, mmu->pdptrs[0]);
> +		vmcs_write64(GUEST_PDPTR1, mmu->pdptrs[1]);
> +		vmcs_write64(GUEST_PDPTR2, mmu->pdptrs[2]);
> +		vmcs_write64(GUEST_PDPTR3, mmu->pdptrs[3]);
> +	}
> +}
> +
>  static void ept_load_pdptrs(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_mmu *mmu = vcpu->arch.walk_mmu;
> @@ -8005,6 +8015,7 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = {
>  	.need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
>  	.apic_init_signal_blocked = vmx_apic_init_signal_blocked,
>  	.migrate_timers = vmx_migrate_timers,
> +	.load_pdptrs = vmx_load_pdptrs,
>  };
>  
>  static __init int hardware_setup(void)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 599d73206299..e52c2d67ba0a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -769,7 +769,8 @@ int load_pdptrs(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, unsigned long cr3)
>  	memcpy(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs));
>  	kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR);
>  
> +	if (kvm_x86_ops.load_pdptrs)
> +		kvm_x86_ops.load_pdptrs(vcpu, mmu);
>  out:
>  
>  	return ret;
> -- 

I'd prefer to handle this on the switch from L2->L1.  It avoids adding a
kvm_x86_ops and yet another sequence of four VMWRITEs, e.g. I think this
will do the trick.

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 9c74a732b08d..67465f0ca1b9 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4356,6 +4356,9 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
        if (kvm_check_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu))
                kvm_vcpu_flush_tlb_current(vcpu);

+       if (enable_ept && is_pae_paging(vcpu))
+               ept_load_pdptrs(vcpu);
+
        leave_guest_mode(vcpu);

        if (nested_cpu_has_preemption_timer(vmcs12))
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 40f5a3923d5b..aa1f259ee47a 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -320,6 +320,7 @@ void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
 int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
 void set_cr4_guest_host_mask(struct vcpu_vmx *vmx);
 void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long cr3);
+void ept_load_pdptrs(struct kvm_vcpu *vcpu);
 void ept_save_pdptrs(struct kvm_vcpu *vcpu);
 void vmx_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg);
 void vmx_set_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg);