On 1/9/2025 7:07 PM, Francesco Lavra wrote:
On 2024-10-30 at 19:00, Rick Edgecombe wrote:
@@ -1055,6 +1144,81 @@ static int tdx_td_vcpu_init(struct kvm_vcpu
*vcpu, u64 vcpu_rcx)
return ret;
}
+/* Sometimes reads multipple subleafs. Return how many enties were
written. */
+static int tdx_vcpu_get_cpuid_leaf(struct kvm_vcpu *vcpu, u32 leaf,
int max_cnt,
+ struct kvm_cpuid_entry2
*output_e)
+{
+ int i;
+
+ if (!max_cnt)
+ return 0;
+
+ /* First try without a subleaf */
+ if (!tdx_read_cpuid(vcpu, leaf, 0, false, output_e))
+ return 1;
+
+ /*
+ * If the try without a subleaf failed, try reading subleafs
until
+ * failure. The TDX module only supports 6 bits of subleaf
index.
It actually supports 7 bits, i.e. bits 6:0, so the limit below should
be 0b1111111.
Nice catch!
+ */
+ for (i = 0; i < 0b111111; i++) {
+ if (i > max_cnt)
+ goto out;
This will make this function return (max_cnt + 1) instead of max_cnt.
I think the code would be simpler if max_cnt was initialized to
min(max_cnt, 0x80) (because 0x7f is a supported subleaf index, as far
as I can tell), and the for() condition was changed to `i < max_cnt`.
Looks better.
+ /* Keep reading subleafs until there is a failure.
*/
+ if (tdx_read_cpuid(vcpu, leaf, i, true, output_e))
+ return i;
+
+ output_e++;
here the output_e++ can overflow the buffer.
+ }
+
+out:
+ return i;
+}
+
+static int tdx_vcpu_get_cpuid(struct kvm_vcpu *vcpu, struct
kvm_tdx_cmd *cmd)
+{
+ struct kvm_cpuid2 __user *output, *td_cpuid;
+ struct kvm_cpuid_entry2 *output_e;
+ int r = 0, i = 0, leaf;
+
+ output = u64_to_user_ptr(cmd->data);
+ td_cpuid = kzalloc(sizeof(*td_cpuid) +
+ sizeof(output->entries[0]) *
KVM_MAX_CPUID_ENTRIES,
+ GFP_KERNEL);
+ if (!td_cpuid)
+ return -ENOMEM;
+
+ for (leaf = 0; leaf <= 0x1f; leaf++) {
+ output_e = &td_cpuid->entries[i];
+ i += tdx_vcpu_get_cpuid_leaf(vcpu, leaf,
+ KVM_MAX_CPUID_ENTRIES -
i - 1,
This should be KVM_MAX_CPUID_ENTRIES - i.
Nice catch!
+ output_e);
+ }
+
+ for (leaf = 0x80000000; leaf <= 0x80000008; leaf++) {
+ output_e = &td_cpuid->entries[i];
+ i += tdx_vcpu_get_cpuid_leaf(vcpu, leaf,
+ KVM_MAX_CPUID_ENTRIES -
i - 1,
Same here.
