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i386/tdx: Don't treat SYSCALL as unavailable

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On Intel CPU, the value of CPUID_EXT2_SYSCALL depends on the mode of
the vcpu. It's 0 outside 64-bit mode and 1 in 64-bit mode.

The initial state of TDX vcpu is 32-bit protected mode. At the time of
calling KVM_TDX_GET_CPUID, vcpu hasn't started running so the value read
is 0.

In reality, 64-bit mode should always be supported. So mark
CPUID_EXT2_SYSCALL always supported to avoid false warning.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250508150002.689633-53-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Xiaoyao Li
2025-05-28 19:35:55 +02:00
committed by Paolo Bonzini
parent e3d1a4a6d1
commit deb9db6fb7
1 changed files with 13 additions and 0 deletions
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target/i386/kvm/tdx.c
+13
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@@ -845,6 +845,19 @@ static int tdx_check_features(X86ConfidentialGuest *cg, CPUState *cs)
continue;
}
/* Fixup for special cases */
switch (w) {
case FEAT_8000_0001_EDX:
/*
* Intel enumerates SYSCALL bit as 1 only when processor in 64-bit
* mode and before vcpu running it's not in 64-bit mode.
*/
actual |= CPUID_EXT2_SYSCALL;
break;
default:
break;
}
requested = env->features[w];
unavailable = requested & ~actual;
mark_unavailable_features(cpu, w, unavailable, unav_prefix);