[PATCH 08/25] KVM: TDX: Add place holder for TDX VM specific mem_enc_op ioctl

Rick Edgecombe
2024-08-12T22:48:36Z

From: Isaku Yamahata <isaku.yamahata@intel.com>

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.

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. Make mem_enc_ioctl non-optional as it's always filled.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
---
uAPI breakout v1:
- rename error->hw_error (Kai)
- Include "x86_ops.h" to tdx.c as the patch to initialize TDX module
doesn't include it anymore.
- Introduce tdx_vm_ioctl() as the first tdx func in x86_ops.h
- Drop middle paragraph in the commit log (Tony)

v15:
- change struct kvm_tdx_cmd to drop unused member.
---
arch/x86/include/asm/kvm-x86-ops.h | 2 +-
arch/x86/include/uapi/asm/kvm.h | 26 ++++++++++++++++++++++++
arch/x86/kvm/vmx/main.c | 10 ++++++++++
arch/x86/kvm/vmx/tdx.c | 32 ++++++++++++++++++++++++++++++
arch/x86/kvm/vmx/x86_ops.h | 6 ++++++
arch/x86/kvm/x86.c | 4 ----
6 files changed, 75 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index af58cabcf82f..538f50eee86d 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -123,7 +123,7 @@ KVM_X86_OP(leave_smm)
KVM_X86_OP(enable_smi_window)
#endif
KVM_X86_OP_OPTIONAL(dev_get_attr)
-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/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index cba4351b3091..d91f1bad800e 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -926,4 +926,30 @@ struct kvm_hyperv_eventfd {
#define KVM_X86_SNP_VM 4
#define KVM_X86_TDX_VM 5

+/* Trust Domain eXtension sub-ioctl() commands. */
+enum kvm_tdx_cmd_id {
+ KVM_TDX_CAPABILITIES = 0,
+
+ KVM_TDX_CMD_NR_MAX,
+};
+
+struct kvm_tdx_cmd {
+ /* enum kvm_tdx_cmd_id */
+ __u32 id;
+ /* flags for sub-commend. If sub-command doesn't use this, set zero. */
+ __u32 flags;
+ /*
+ * data for each sub-command. An immediate or a pointer to the actual
+ * data in process virtual address. If sub-command doesn't use it,
+ * set zero.
+ */
+ __u64 data;
+ /*
+ * Auxiliary error code. The sub-command may return TDX SEAMCALL
+ * status code in addition to -Exxx.
+ * Defined for consistency with struct kvm_sev_cmd.
+ */
+ __u64 hw_error;
+};
+
#endif /* _ASM_X86_KVM_H */
diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
index 21fae631c775..59f4d2d42620 100644
--- a/arch/x86/kvm/vmx/main.c
+++ b/arch/x86/kvm/vmx/main.c
@@ -41,6 +41,14 @@ static __init int vt_hardware_setup(void)
return 0;
}

+static int vt_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
+{
+ if (!is_td(kvm))
+ return -ENOTTY;
+
+ return tdx_vm_ioctl(kvm, argp);
+}
+
#define VMX_REQUIRED_APICV_INHIBITS \
(BIT(APICV_INHIBIT_REASON_DISABLED) | \
BIT(APICV_INHIBIT_REASON_ABSENT) | \
@@ -189,6 +197,8 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
.vcpu_deliver_sipi_vector = kvm_vcpu_deliver_sipi_vector,

.get_untagged_addr = vmx_get_untagged_addr,
+
+ .mem_enc_ioctl = vt_mem_enc_ioctl,
};

struct kvm_x86_init_ops vt_init_ops __initdata = {
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index b1c885ce8c9c..de14e80d8f3a 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -2,6 +2,7 @@
#include <linux/cpu.h>
#include <asm/tdx.h>
#include "capabilities.h"
+#include "x86_ops.h"
#include "tdx.h"

#undef pr_fmt
@@ -29,6 +30,37 @@ static void __used tdx_guest_keyid_free(int keyid)
ida_free(&tdx_guest_keyid_pool, keyid);
}

+int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
+{
+ struct kvm_tdx_cmd tdx_cmd;
+ int r;
+
+ if (copy_from_user(&tdx_cmd, argp, sizeof(struct kvm_tdx_cmd)))
+ return -EFAULT;
+
+ /*
+ * Userspace should never set @error. It is used to fill
+ * hardware-defined error by the kernel.
+ */
+ if (tdx_cmd.hw_error)
+ return -EINVAL;
+
+ mutex_lock(&kvm->lock);
+
+ switch (tdx_cmd.id) {
+ default:
+ r = -EINVAL;
+ goto out;
+ }
+
+ if (copy_to_user(argp, &tdx_cmd, sizeof(struct kvm_tdx_cmd)))
+ r = -EFAULT;
+
+out:
+ mutex_unlock(&kvm->lock);
+ return r;
+}
+
static int tdx_online_cpu(unsigned int cpu)
{
unsigned long flags;
diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
index 133afc4d196e..c69ca640abe6 100644
--- a/arch/x86/kvm/vmx/x86_ops.h
+++ b/arch/x86/kvm/vmx/x86_ops.h
@@ -118,4 +118,10 @@ void vmx_cancel_hv_timer(struct kvm_vcpu *vcpu);
#endif
void vmx_setup_mce(struct kvm_vcpu *vcpu);

+#ifdef CONFIG_INTEL_TDX_HOST
+int tdx_vm_ioctl(struct kvm *kvm, void __user *argp);
+#else
+static inline int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) { return -EOPNOTSUPP; }
+#endif
+
#endif /* __KVM_X86_VMX_X86_OPS_H */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a8944266a54d..7914ea50fd04 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7313,10 +7313,6 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
goto out;
}
case KVM_MEMORY_ENCRYPT_OP: {
- r = -ENOTTY;
- if (!kvm_x86_ops.mem_enc_ioctl)
- goto out;
-
r = kvm_x86_call(mem_enc_ioctl)(kvm, argp);
break;
}
--
2.34.1