Re: [PATCH v19 067/130] KVM: TDX: Add load_mmu_pgd method for TDX

[Binbin Wu]

On 2/26/2024 4:26 PM, isaku.yamahata@xxxxxxxxx wrote:
> From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
>
> For virtual IO, the guest TD shares guest pages with VMM without
> encryption.

Virtual IO is a use case of shared memory, it's better to use it
as a example instead of putting it at the beginning of the sentence.


>   Shared EPT is used to map guest pages in unprotected way.
>
> Add the VMCS field encoding for the shared EPTP, which will be used by
> TDX to have separate EPT walks for private GPAs (existing EPTP) versus
> shared GPAs (new shared EPTP).
>
> Set shared EPT pointer value for the TDX guest to initialize TDX MMU.
May have a mention that the EPTP for priavet GPAs is set by TDX module.

> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> v19:
> - Add WARN_ON_ONCE() to tdx_load_mmu_pgd() and drop unconditional mask
> ---
>   arch/x86/include/asm/vmx.h |  1 +
>   arch/x86/kvm/vmx/main.c    | 13 ++++++++++++-
>   arch/x86/kvm/vmx/tdx.c     |  6 ++++++
>   arch/x86/kvm/vmx/x86_ops.h |  4 ++++
>   4 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index f703bae0c4ac..9deb663a42e3 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -236,6 +236,7 @@ enum vmcs_field {
>   	TSC_MULTIPLIER_HIGH             = 0x00002033,
>   	TERTIARY_VM_EXEC_CONTROL	= 0x00002034,
>   	TERTIARY_VM_EXEC_CONTROL_HIGH	= 0x00002035,
> +	SHARED_EPT_POINTER		= 0x0000203C,
>   	PID_POINTER_TABLE		= 0x00002042,
>   	PID_POINTER_TABLE_HIGH		= 0x00002043,
>   	GUEST_PHYSICAL_ADDRESS          = 0x00002400,
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index d0f75020579f..076a471d9aea 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -123,6 +123,17 @@ static void vt_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>   	vmx_vcpu_reset(vcpu, init_event);
>   }
>   
> +static void vt_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa,
> +			int pgd_level)
> +{
> +	if (is_td_vcpu(vcpu)) {
> +		tdx_load_mmu_pgd(vcpu, root_hpa, pgd_level);
> +		return;
> +	}
> +
> +	vmx_load_mmu_pgd(vcpu, root_hpa, pgd_level);
> +}
> +
>   static int vt_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
>   {
>   	if (!is_td(kvm))
> @@ -256,7 +267,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
>   	.write_tsc_offset = vmx_write_tsc_offset,
>   	.write_tsc_multiplier = vmx_write_tsc_multiplier,
>   
> -	.load_mmu_pgd = vmx_load_mmu_pgd,
> +	.load_mmu_pgd = vt_load_mmu_pgd,
>   
>   	.check_intercept = vmx_check_intercept,
>   	.handle_exit_irqoff = vmx_handle_exit_irqoff,
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 54e0d4efa2bd..143a3c2a16bc 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -453,6 +453,12 @@ void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>   	 */
>   }
>   
> +void tdx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, int pgd_level)
> +{
> +	WARN_ON_ONCE(root_hpa & ~PAGE_MASK);
> +	td_vmcs_write64(to_tdx(vcpu), SHARED_EPT_POINTER, root_hpa);
> +}
> +
>   static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd)
>   {
>   	struct kvm_tdx_capabilities __user *user_caps;
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index f5820f617b2e..24161fa404aa 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -152,6 +152,8 @@ void tdx_vcpu_free(struct kvm_vcpu *vcpu);
>   void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event);
>   
>   int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp);
> +
> +void tdx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, int root_level);
>   #else
>   static inline int tdx_hardware_setup(struct kvm_x86_ops *x86_ops) { return -EOPNOTSUPP; }
>   static inline void tdx_hardware_unsetup(void) {}
> @@ -173,6 +175,8 @@ static inline void tdx_vcpu_free(struct kvm_vcpu *vcpu) {}
>   static inline void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) {}
>   
>   static inline int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp) { return -EOPNOTSUPP; }
> +
> +static inline void tdx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, int root_level) {}
>   #endif
>   
>   #endif /* __KVM_X86_VMX_X86_OPS_H */