Re: [RFC PATCH v5 025/104] KVM: TDX: Add place holder for TDX VM specific mem_enc_op ioctl

From: Paolo Bonzini
Date: Tue Apr 05 2022 - 19:35:20 EST

On 3/4/22 20:48, isaku.yamahata@xxxxxxxxx wrote:
From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

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

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, and VCPU-scoped TDX-specific operations for device
model, for example, qemu. Getting system-wide parameters, TDX-specific VM
initialization, and TDX-specific vCPU initialization. Which requires KVM
vCPU-scoped operations in addition to the existing VM-scoped operations.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
arch/x86/include/uapi/asm/kvm.h | 11 +++++++++++
arch/x86/kvm/vmx/main.c | 10 ++++++++++
arch/x86/kvm/vmx/tdx.c | 24 ++++++++++++++++++++++++
arch/x86/kvm/vmx/x86_ops.h | 4 ++++
tools/arch/x86/include/uapi/asm/kvm.h | 11 +++++++++++
5 files changed, 60 insertions(+)

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 71a5851475e7..2ad61caf4e0b 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -528,4 +528,15 @@ struct kvm_pmu_event_filter {
#define KVM_X86_DEFAULT_VM 0
#define KVM_X86_TDX_VM 1
+/* Trust Domain eXtension sub-ioctl() commands. */
+enum kvm_tdx_cmd_id {
+struct kvm_tdx_cmd {
+ __u32 id;
+ __u32 metadata;
+ __u64 data;

Please include some initial documentation here already, for example it is not clear what "metadata" is.

Also please add

u32 error;
u32 unused;

for two reasons: 1) consistency with kvm_sev_cmd 2) error codes should be returned to userspace and not just sent through pr_tdx_error.