qemu-kvm/kvm-i386-tdx-Get-tdx_capabilities-via-KVM_TDX_CAPABILITI.patch

From 5c6bd0700ee50d40a791c1a00c475f9042e23343 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 18 Jul 2025 18:03:45 +0200
Subject: [PATCH 034/115] i386/tdx: Get tdx_capabilities via
 KVM_TDX_CAPABILITIES

RH-Author: Paolo Bonzini <pbonzini@redhat.com>
RH-MergeRequest: 391: TDX support, including attestation and device assignment
RH-Jira: RHEL-15710 RHEL-20798 RHEL-49728
RH-Acked-by: Yash Mankad <None>
RH-Acked-by: Peter Xu <peterx@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Commit: [34/115] bd4711c0cf17e73ea2f21417b6b031c9118a35c6 (bonzini/rhel-qemu-kvm)

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 <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20250508150002.689633-6-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 8eddedc3701d2190db976a05155a8263c8ec175b)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 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(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 12da34b9c5..bf4493dd84 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1771,8 +1771,6 @@ 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 7edb154a16..499691e8d0 100644
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -13,6 +13,8 @@
 
 #include "sysemu/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 4ff9486081..c67be5e618 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)
-- 
2.50.1