linux-kernel - Re: [PATCH v11 016/113] KVM: TDX: Add place holder for TDX VM specific mem_enc

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Message-ID: <19645255d65fdfd184b92b5192cac83a27c430fb.camel@intel.com>
Date:   Thu, 19 Jan 2023 02:40:17 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
CC:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>
Subject: Re: [PATCH v11 016/113] KVM: TDX: Add place holder for TDX VM
 specific mem_enc_op ioctl

On Thu, 2023-01-12 at 08:31 -0800, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> Add a place holder function for TDX specific VM-scoped ioctl as mem_enc_op.
> TDX specific sub-commands will be added to retrieve/pass TDX specific
> parameters.
> 
> KVM_MEMORY_ENCRYPT_OP was introduced for VM-scoped operations specific for
> guest state-protected VM.  It defined subcommands for technology-specific
> operations under KVM_MEMORY_ENCRYPT_OP.  Despite its name, the subcommands
> are not limited to memory encryption, but various technology-specific
> operations are defined.  It's natural to repurpose KVM_MEMORY_ENCRYPT_OP
> for TDX specific operations and define subcommands.
> 
> TDX requires VM-scoped TDX-specific operations for device model, for
> example, qemu.  Getting system-wide parameters, TDX-specific VM
> initialization.

There's grammar issue in the last paragraph.  Please use grammar check.

> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>  arch/x86/kvm/vmx/main.c    |  9 +++++++++
>  arch/x86/kvm/vmx/tdx.c     | 26 ++++++++++++++++++++++++++
>  arch/x86/kvm/vmx/x86_ops.h |  4 ++++
>  3 files changed, 39 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index 16053ec3e0ae..781fbc896120 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -37,6 +37,14 @@ static int vt_vm_init(struct kvm *kvm)
>  	return vmx_vm_init(kvm);
>  }
>  
> +static int vt_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
> +{
> +	if (!is_td(kvm))
> +		return -ENOTTY;
> +
> +	return tdx_vm_ioctl(kvm, argp);
> +}
> +
>  struct kvm_x86_ops vt_x86_ops __initdata = {
>  	.name = KBUILD_MODNAME,
>  
> @@ -179,6 +187,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
>  	.vcpu_deliver_sipi_vector = kvm_vcpu_deliver_sipi_vector,
>  
>  	.dev_mem_enc_ioctl = tdx_dev_ioctl,
> +	.mem_enc_ioctl = vt_mem_enc_ioctl,
>  };

IIUC, now both AMD and Intel have mem_enc_ioctl() callback implemented, so the
KVM_X86_OP_OPTIONAL() of it can be changed to KVM_X86_OP(), and the function
pointer check can be removed in the IOCTL:

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-
ops.h
index 8dc345cc6318..a59852fb5e2a 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -116,7 +116,7 @@ KVM_X86_OP(enter_smm)
 KVM_X86_OP(leave_smm)
 KVM_X86_OP(enable_smi_window)
 #endif
-KVM_X86_OP_OPTIONAL(mem_enc_ioctl)
+KVM_X86_OP(mem_enc_ioctl)
 KVM_X86_OP_OPTIONAL(mem_enc_register_region)
 KVM_X86_OP_OPTIONAL(mem_enc_unregister_region)
 KVM_X86_OP_OPTIONAL(vm_copy_enc_context_from)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c936f8d28a53..dfa279e35478 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6937,10 +6937,6 @@ long kvm_arch_vm_ioctl(struct file *filp,
                goto out;
        }
        case KVM_MEMORY_ENCRYPT_OP: {
-               r = -ENOTTY;
-               if (!kvm_x86_ops.mem_enc_ioctl)
-                       goto out;
-
                r = static_call(kvm_x86_mem_enc_ioctl)(kvm, argp);
                break;
        }

[snip]