target-i386: Don't try to enable PT State xsave component
The code that calculates the set of supported XSAVE components on CPUID looks at ext_save_areas to find out which components should be enabled. However, if there are zeroed entries in the ext_save_areas array, the ((env->features[esa->feature] & esa->bits) == esa->bits) check will always succeed and QEMU will unconditionally try to enable the component. Luckily this never caused any problems because the only missing entry in ext_save_areas is the PT State component (bit 8), and KVM currently doesn't support it (so it was cleared on ena_mask). But the code was still incorrect and would break if KVM starts returning CPUID[EAX=0xD,ECX=0].EAX[bit 8] as supported on GET_SUPPORTED_CPUID. Fix the problem by changing the code to not enable a XSAVE component if ExtSaveArea::bits is zero. Reviewed-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
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@ -2514,7 +2514,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
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*ecx = 0x240;
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for (i = 2; i < ARRAY_SIZE(x86_ext_save_areas); i++) {
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const ExtSaveArea *esa = &x86_ext_save_areas[i];
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if ((env->features[esa->feature] & esa->bits) == esa->bits
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if ((env->features[esa->feature] & esa->bits)
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&& ((ena_mask >> i) & 1) != 0) {
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if (i < 32) {
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*eax |= 1u << i;
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@ -2530,7 +2530,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
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*eax = env->features[FEAT_XSAVE];
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} else if (count < ARRAY_SIZE(x86_ext_save_areas)) {
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const ExtSaveArea *esa = &x86_ext_save_areas[count];
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if ((env->features[esa->feature] & esa->bits) == esa->bits
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if ((env->features[esa->feature] & esa->bits)
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&& ((ena_mask >> count) & 1) != 0) {
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*eax = esa->size;
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*ebx = esa->offset;
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@ -2766,7 +2766,7 @@ static void x86_cpu_reset(CPUState *s)
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}
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for (i = 2; i < ARRAY_SIZE(x86_ext_save_areas); i++) {
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const ExtSaveArea *esa = &x86_ext_save_areas[i];
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if ((env->features[esa->feature] & esa->bits) == esa->bits) {
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if (env->features[esa->feature] & esa->bits) {
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xcr0 |= 1ull << i;
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}
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}
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