[PATCH V2 10/12] KVM: TDX: Disable support for TSX and WAITPKG

Adrian Hunter
2025-01-29T10:00:27Z

Support for restoring IA32_TSX_CTRL MSR and IA32_UMWAIT_CONTROL MSR is not
yet implemented, so disable support for TSX and WAITPKG for now. Clear the
associated CPUID bits returned by KVM_TDX_CAPABILITIES, and return an error
if those bits are set in KVM_TDX_INIT_VM.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
TD vcpu enter/exit v2:
- New patch
---
arch/x86/kvm/vmx/tdx.c | 43 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 43 insertions(+)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index a0f5cdfd290b..70996af4be64 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -117,6 +117,44 @@ static u32 tdx_set_guest_phys_addr_bits(const u32 eax, int addr_bits)
return (eax & ~GENMASK(23, 16)) | (addr_bits & 0xff) << 16;
}

+#define TDX_FEATURE_TSX (__feature_bit(X86_FEATURE_HLE) | __feature_bit(X86_FEATURE_RTM))
+
+static bool has_tsx(const struct kvm_cpuid_entry2 *entry)
+{
+ return entry->function == 7 && entry->index == 0 &&
+ (entry->ebx & TDX_FEATURE_TSX);
+}
+
+static void clear_tsx(struct kvm_cpuid_entry2 *entry)
+{
+ entry->ebx &= ~TDX_FEATURE_TSX;
+}
+
+static bool has_waitpkg(const struct kvm_cpuid_entry2 *entry)
+{
+ return entry->function == 7 && entry->index == 0 &&
+ (entry->ecx & __feature_bit(X86_FEATURE_WAITPKG));
+}
+
+static void clear_waitpkg(struct kvm_cpuid_entry2 *entry)
+{
+ entry->ecx &= ~__feature_bit(X86_FEATURE_WAITPKG);
+}
+
+static void tdx_clear_unsupported_cpuid(struct kvm_cpuid_entry2 *entry)
+{
+ if (has_tsx(entry))
+ clear_tsx(entry);
+
+ if (has_waitpkg(entry))
+ clear_waitpkg(entry);
+}
+
+static bool tdx_unsupported_cpuid(const struct kvm_cpuid_entry2 *entry)
+{
+ return has_tsx(entry) || has_waitpkg(entry);
+}
+
#define KVM_TDX_CPUID_NO_SUBLEAF ((__u32)-1)

static void td_init_cpuid_entry2(struct kvm_cpuid_entry2 *entry, unsigned char idx)
@@ -140,6 +178,8 @@ static void td_init_cpuid_entry2(struct kvm_cpuid_entry2 *entry, unsigned char i
*/
if (entry->function == 0x80000008)
entry->eax = tdx_set_guest_phys_addr_bits(entry->eax, 0xff);
+
+ tdx_clear_unsupported_cpuid(entry);
}

static int init_kvm_tdx_caps(const struct tdx_sys_info_td_conf *td_conf,
@@ -1214,6 +1254,9 @@ static int setup_tdparams_cpuids(struct kvm_cpuid2 *cpuid,
if (!entry)
continue;

+ if (tdx_unsupported_cpuid(entry))
+ return -EINVAL;
+
copy_cnt++;

value = &td_params->cpuid_values[i];
--
2.43.0