Re: [PATCH v19 069/130] KVM: TDX: Require TDP MMU and mmio caching for TDX

Binbin Wu
2024-03-28T05:24:34Z

On 2/26/2024 4:26 PM, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> As TDP MMU is becoming main stream than the legacy MMU, the legacy MMU
> support for TDX isn't implemented. TDX requires KVM mmio caching.

Can you add some description about why TDX requires mmio caching in the
changelog?

> Disable
> TDX support when TDP MMU or mmio caching aren't supported.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> arch/x86/kvm/mmu/mmu.c | 1 +
> arch/x86/kvm/vmx/main.c | 13 +++++++++++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 0e0321ad9ca2..b8d6ce02e66d 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -104,6 +104,7 @@ module_param_named(flush_on_reuse, force_flush_and_sync_on_reuse, bool, 0644);
> * If the hardware supports that we don't need to do shadow paging.
> */
> bool tdp_enabled = false;
> +EXPORT_SYMBOL_GPL(tdp_enabled);
>
> static bool __ro_after_init tdp_mmu_allowed;
>
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index 076a471d9aea..54df6653193e 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -3,6 +3,7 @@
>
> #include "x86_ops.h"
> #include "vmx.h"
> +#include "mmu.h"
> #include "nested.h"
> #include "pmu.h"
> #include "tdx.h"
> @@ -36,6 +37,18 @@ static __init int vt_hardware_setup(void)
> if (ret)
> return ret;
>
> + /* TDX requires KVM TDP MMU. */
> + if (enable_tdx && !tdp_enabled) {
> + enable_tdx = false;
> + pr_warn_ratelimited("TDX requires TDP MMU. Please enable TDP MMU for TDX.\n");
> + }
> +
> + /* TDX requires MMIO caching. */
> + if (enable_tdx && !enable_mmio_caching) {
> + enable_tdx = false;
> + pr_warn_ratelimited("TDX requires mmio caching. Please enable mmio caching for TDX.\n");
> + }
> +
> enable_tdx = enable_tdx && !tdx_hardware_setup(&vt_x86_ops);
> if (enable_tdx)
> vt_x86_ops.vm_size = max_t(unsigned int, vt_x86_ops.vm_size,