2023-01-12 16:48:27

by Isaku Yamahata

Subject: [PATCH v11 039/113] KVM: x86/mmu: Require TDP MMU for TDX

From: Isaku Yamahata <[email protected]>

Require the TDP MMU for guest TDs, the so called "shadow" MMU does not
support mapping guest private memory, i.e. does not support Secure-EPT.

Signed-off-by: Isaku Yamahata <[email protected]>
---
arch/x86/kvm/mmu/tdp_mmu.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index fdcff390ebc2..6c3ce4121a46 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -27,6 +27,13 @@ int kvm_mmu_init_tdp_mmu(struct kvm *kvm)
if (kvm->arch.vm_type == KVM_X86_TDX_VM && !enable_mmio_caching)
return -EOPNOTSUPP;

+ /*
+ * Because only the TDP MMU supports TDX, require the TDP MMU for guest
+ * TDs.
+ */
+ if (kvm->arch.vm_type == KVM_X86_TDX_VM && !tdp_enabled)
+ return -EOPNOTSUPP;
+
if (!tdp_enabled || !READ_ONCE(tdp_mmu_enabled))
return 0;

--
2.25.1

2023-01-19 12:28:55

by Kai Huang

Subject: Re: [PATCH v11 039/113] KVM: x86/mmu: Require TDP MMU for TDX

On Thu, 2023-01-12 at 08:31 -0800, [email protected] wrote:
> From: Isaku Yamahata <[email protected]>
>
> Require the TDP MMU for guest TDs, the so called "shadow" MMU does not
> support mapping guest private memory, i.e. does not support Secure-EPT.

It's not accurate. Legacy MMU using EPT can also support. We just choose to
not support. Please revisit.

>
> Signed-off-by: Isaku Yamahata <[email protected]>
> ---
> arch/x86/kvm/mmu/tdp_mmu.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index fdcff390ebc2..6c3ce4121a46 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -27,6 +27,13 @@ int kvm_mmu_init_tdp_mmu(struct kvm *kvm)
> if (kvm->arch.vm_type == KVM_X86_TDX_VM && !enable_mmio_caching)
> return -EOPNOTSUPP;
>
> + /*
> + * Because only the TDP MMU supports TDX, require the TDP MMU for guest
> + * TDs.
> + */
> + if (kvm->arch.vm_type == KVM_X86_TDX_VM && !tdp_enabled)
> + return -EOPNOTSUPP;
> +
> if (!tdp_enabled || !READ_ONCE(tdp_mmu_enabled))
> return 0;
>