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target-i386: Don't try to enable PT State xsave component

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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>
This commit is contained in:
Eduardo Habkost 2016-09-22 18:58:39 -03:00
parent 2d5312da56
commit 9646f4927f
1 changed files with 3 additions and 3 deletions
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6
target-i386/cpu.c
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@ -2514,7 +2514,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
*ecx = 0x240;
for (i = 2; i < ARRAY_SIZE(x86_ext_save_areas); i++) {
const ExtSaveArea *esa = &x86_ext_save_areas[i];
if ((env->features[esa->feature] & esa->bits) == esa->bits
if ((env->features[esa->feature] & esa->bits)
&& ((ena_mask >> i) & 1) != 0) {
if (i < 32) {
*eax |= 1u << i;
@ -2530,7 +2530,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
*eax = env->features[FEAT_XSAVE];
} else if (count < ARRAY_SIZE(x86_ext_save_areas)) {
const ExtSaveArea *esa = &x86_ext_save_areas[count];
if ((env->features[esa->feature] & esa->bits) == esa->bits
if ((env->features[esa->feature] & esa->bits)
&& ((ena_mask >> count) & 1) != 0) {
*eax = esa->size;
*ebx = esa->offset;
@ -2766,7 +2766,7 @@ static void x86_cpu_reset(CPUState *s)
}
for (i = 2; i < ARRAY_SIZE(x86_ext_save_areas); i++) {
const ExtSaveArea *esa = &x86_ext_save_areas[i];
if ((env->features[esa->feature] & esa->bits) == esa->bits) {
if (env->features[esa->feature] & esa->bits) {
xcr0 |= 1ull << i;
}
}