i386/tdx: Add XFD to supported bit of TDX

Just mark XFD as always supported for TDX. This simple solution relies
on the fact KVM will report XFD as 0 when it's not supported by the
hardware.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250508150002.689633-49-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index b38e691f1af3fbc3dcd6158b2c742151e7c61e6e..8a4b4217d02169e0da2df7bcd21494acb8f73851 100644 (file)
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1122,6 +1122,7 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord w);
 #define CPUID_XSAVE_XSAVEC     (1U << 1)
 #define CPUID_XSAVE_XGETBV1    (1U << 2)
 #define CPUID_XSAVE_XSAVES     (1U << 3)
+#define CPUID_XSAVE_XFD        (1U << 4)
 
 #define CPUID_6_EAX_ARAT       (1U << 2)
 

diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 188c2242d534784ced5127cf3558efb0902518cd..0f7f47c6da873725743030e550c9a8257b6c9065 100644 (file)
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -621,6 +621,12 @@ static void tdx_add_supported_cpuid_by_xfam(void)
     e->edx |= (tdx_caps->supported_xfam & CPUID_XSTATE_XCR0_MASK) >> 32;
 
     e = find_in_supported_entry(0xd, 1);
+    /*
+     * Mark XFD always support for TDX, it will be cleared finally in
+     * tdx_adjust_cpuid_features() if XFD is unavailable on the hardware
+     * because in this case the original data has it as 0.
+     */
+    e->eax |= CPUID_XSAVE_XFD;
     e->ecx |= (tdx_caps->supported_xfam & CPUID_XSTATE_XSS_MASK);
     e->edx |= (tdx_caps->supported_xfam & CPUID_XSTATE_XSS_MASK) >> 32;
 }