From: Phil Dennis-Jordan <p...@philjordan.eu> The handling for CPUID function 0xD (supported XSAVE features) was improved in a recent patch. Unfortunately, this appears to have introduced undefined behaviour for cases where ecx > 30, as the result of (1 << idx) is undefined if idx > 30.
Per Intel SDM section 13.2, the behaviour for ecx values up to and including 62 are specified. This change therefore specifically sets all registers returned by the CPUID instruction to 0 for 63 and higher. Furthermore, the bit shift uses uint64_t, where behaviour for the entire range of 2..62 is safe and correct. Signed-off-by: Phil Dennis-Jordan <p...@philjordan.eu> Link: https://lore.kernel.org/r/20241105155800.5461-3-p...@philjordan.eu Reviewed-by: Roman Bolshakov <r.bolsha...@yadro.com> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> --- target/i386/hvf/x86_cpuid.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/target/i386/hvf/x86_cpuid.c b/target/i386/hvf/x86_cpuid.c index 3f16b0f363d..af9ee17a111 100644 --- a/target/i386/hvf/x86_cpuid.c +++ b/target/i386/hvf/x86_cpuid.c @@ -119,8 +119,8 @@ uint32_t hvf_get_supported_cpuid(uint32_t func, uint32_t idx, eax = 0; break; case 0xD: - if (!supported_xcr0 || - (idx > 1 && !(supported_xcr0 & (1 << idx)))) { + if (!supported_xcr0 || idx >= 63 || + (idx > 1 && !(supported_xcr0 & (UINT64_C(1) << idx)))) { eax = ebx = ecx = edx = 0; break; } -- 2.47.0
