[v7,05/52] i386/tdx: Get tdx_capabilities via KVM_TDX_CAPABILITIES

Commit Message

Xiaoyao Li Jan. 24, 2025, 1:20 p.m. UTC

KVM provides TDX capabilities via sub command KVM_TDX_CAPABILITIES of
IOCTL(KVM_MEMORY_ENCRYPT_OP). Get the capabilities when initializing
TDX context. It will be used to validate user's setting later.

Since there is no interface reporting how many cpuid configs contains in
KVM_TDX_CAPABILITIES, QEMU chooses to try starting with a known number
and abort when it exceeds KVM_MAX_CPUID_ENTRIES.

Besides, introduce the interfaces to invoke TDX "ioctls" at VCPU scope
in preparation.

Signed-off-by: Xiaoyao Li <[e-mail]>
---
Changes in v7:
- refine and unifiy the error handling; (Daniel)

Changes in v6:
- Pass CPUState * to tdx_vcpu_ioctl();
- update commit message to remove platform scope thing;
- dump hw_error when it's non-zero to help debug;

Changes in v4:
- use {} to initialize struct kvm_tdx_cmd, to avoid memset();
- remove tdx_platform_ioctl() because no user;

Changes in v3:
- rename __tdx_ioctl() to tdx_ioctl_internal()
- Pass errp in get_tdx_capabilities();

changes in v2:
  - Make the error message more clear;

changes in v1:
  - start from nr_cpuid_configs = 6 for the loop;
  - stop the loop when nr_cpuid_configs exceeds KVM_MAX_CPUID_ENTRIES;
---
 target/i386/kvm/kvm.c      |   2 -
 target/i386/kvm/kvm_i386.h |   2 +
 target/i386/kvm/tdx.c      | 107 ++++++++++++++++++++++++++++++++++++-
 3 files changed, 108 insertions(+), 3 deletions(-)

Patch

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 1af4710556ad..b4fa35405fe1 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1779,8 +1779,6 @@  static int hyperv_init_vcpu(X86CPU *cpu)
 
 static Error *invtsc_mig_blocker;
 
-#define KVM_MAX_CPUID_ENTRIES  100
-
 static void kvm_init_xsave(CPUX86State *env)
 {
     if (has_xsave2) {
diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
index 88565e8dbac1..ed1e61fb8ba9 100644
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -13,6 +13,8 @@ 
 
 #include "system/kvm.h"
 
+#define KVM_MAX_CPUID_ENTRIES  100
+
 /* always false if !CONFIG_KVM */
 #define kvm_pit_in_kernel() \
     (kvm_irqchip_in_kernel() && !kvm_irqchip_is_split())
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 4ff94860815d..bd212abab865 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -10,17 +10,122 @@ 
  */
 
 #include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "qapi/error.h"
 #include "qom/object_interfaces.h"
 
 #include "hw/i386/x86.h"
 #include "kvm_i386.h"
 #include "tdx.h"
 
+static struct kvm_tdx_capabilities *tdx_caps;
+
+enum tdx_ioctl_level {
+    TDX_VM_IOCTL,
+    TDX_VCPU_IOCTL,
+};
+
+static int tdx_ioctl_internal(enum tdx_ioctl_level level, void *state,
+                              int cmd_id, __u32 flags, void *data,
+                              Error **errp)
+{
+    struct kvm_tdx_cmd tdx_cmd = {};
+    int r;
+
+    const char* tdx_ioctl_name[] = {
+        [KVM_TDX_CAPABILITIES] = "KVM_TDX_CAPABILITIES",
+        [KVM_TDX_INIT_VM] = "KVM_TDX_INIT_VM",
+        [KVM_TDX_INIT_VCPU] = "KVM_TDX_INIT_VCPU",
+        [KVM_TDX_INIT_MEM_REGION] = "KVM_TDX_INIT_MEM_REGION",
+        [KVM_TDX_FINALIZE_VM] = "KVM_TDX_FINALIZE_VM",
+        [KVM_TDX_GET_CPUID] = "KVM_TDX_GET_CPUID",
+    };
+
+    tdx_cmd.id = cmd_id;
+    tdx_cmd.flags = flags;
+    tdx_cmd.data = (__u64)(unsigned long)data;
+
+    switch (level) {
+    case TDX_VM_IOCTL:
+        r = kvm_vm_ioctl(kvm_state, KVM_MEMORY_ENCRYPT_OP, &tdx_cmd);
+        break;
+    case TDX_VCPU_IOCTL:
+        r = kvm_vcpu_ioctl(state, KVM_MEMORY_ENCRYPT_OP, &tdx_cmd);
+        break;
+    default:
+        error_setg(errp, "Invalid tdx_ioctl_level %d", level);
+        return -EINVAL;
+    }
+
+    if (r < 0) {
+        error_setg_errno(errp, -r, "TDX ioctl %s failed, hw_errors: 0x%llx",
+                         tdx_ioctl_name[cmd_id], tdx_cmd.hw_error);
+    }
+    return r;
+}
+
+static inline int tdx_vm_ioctl(int cmd_id, __u32 flags, void *data,
+                               Error **errp)
+{
+    return tdx_ioctl_internal(TDX_VM_IOCTL, NULL, cmd_id, flags, data, errp);
+}
+
+static inline int tdx_vcpu_ioctl(CPUState *cpu, int cmd_id, __u32 flags,
+                                 void *data, Error **errp)
+{
+    return  tdx_ioctl_internal(TDX_VCPU_IOCTL, cpu, cmd_id, flags, data, errp);
+}
+
+static int get_tdx_capabilities(Error **errp)
+{
+    struct kvm_tdx_capabilities *caps;
+    /* 1st generation of TDX reports 6 cpuid configs */
+    int nr_cpuid_configs = 6;
+    size_t size;
+    int r;
+
+    do {
+        Error *local_err = NULL;
+        size = sizeof(struct kvm_tdx_capabilities) +
+                      nr_cpuid_configs * sizeof(struct kvm_cpuid_entry2);
+        caps = g_malloc0(size);
+        caps->cpuid.nent = nr_cpuid_configs;
+
+        r = tdx_vm_ioctl(KVM_TDX_CAPABILITIES, 0, caps, &local_err);
+        if (r == -E2BIG) {
+            g_free(caps);
+            nr_cpuid_configs *= 2;
+            if (nr_cpuid_configs > KVM_MAX_CPUID_ENTRIES) {
+                error_report("KVM TDX seems broken that number of CPUID entries"
+                             " in kvm_tdx_capabilities exceeds limit: %d",
+                             KVM_MAX_CPUID_ENTRIES);
+                error_propagate(errp, local_err);
+                return r;
+            }
+            error_free(local_err);
+        } else if (r < 0) {
+            g_free(caps);
+            error_propagate(errp, local_err);
+            return r;
+        }
+    } while (r == -E2BIG);
+
+    tdx_caps = caps;
+
+    return 0;
+}
+
 static int tdx_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
 {
+    int r = 0;
+
     kvm_mark_guest_state_protected();
 
-    return 0;
+    if (!tdx_caps) {
+        r = get_tdx_capabilities(errp);
+    }
+
+    return r;
 }
 
 static int tdx_kvm_type(X86ConfidentialGuest *cg)