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

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Date: Thu, 28 Mar 2024 13:24:27 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: isaku.yamahata@...el.com
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
 erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
 Sagi Shahar <sagis@...gle.com>, Kai Huang <kai.huang@...el.com>,
 chen.bo@...el.com, hang.yuan@...el.com, tina.zhang@...el.com
Subject: Re: [PATCH v19 069/130] KVM: TDX: Require TDP MMU and mmio caching
 for TDX



On 2/26/2024 4:26 PM, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.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@...el.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,