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i386: rewrite way CPUID index is validated 

Change the nested if statements into a flat format, to make
it clearer what validation / capping is being performed on
different CPUID index values.

NB this changes behaviour when "index > env->cpuid_xlevel2".
This won't have any guest-visible effect because no there is
no CPUID[0xC0000001] feature supported by TCG, and KVM code
will never call cpu_x86_cpuid() with such an index value.

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <20170509132736.10071-2-berrange@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
This commit is contained in:
Daniel P. Berrange 2017-05-09 14:27:35 +01:00 committed by Eduardo Habkost
parent 76d20ea0f1
commit 4ed3d478c6
1 changed files with 15 additions and 20 deletions
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35
target/i386/cpu.c
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@ -2635,28 +2635,23 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
X86CPU *cpu = x86_env_get_cpu(env);
CPUState *cs = CPU(cpu);
uint32_t pkg_offset;
uint32_t limit;
/* test if maximum index reached */
if (index & 0x80000000) {
if (index > env->cpuid_xlevel) {
if (env->cpuid_xlevel2 > 0) {
/* Handle the Centaur's CPUID instruction. */
if (index > env->cpuid_xlevel2) {
index = env->cpuid_xlevel2;
} else if (index < 0xC0000000) {
index = env->cpuid_xlevel;
}
} else {
/* Intel documentation states that invalid EAX input will
* return the same information as EAX=cpuid_level
* (Intel SDM Vol. 2A - Instruction Set Reference - CPUID)
*/
index = env->cpuid_level;
}
}
/* Calculate & apply limits for different index ranges */
if (index >= 0xC0000000) {
limit = env->cpuid_xlevel2;
} else if (index >= 0x80000000) {
limit = env->cpuid_xlevel;
} else {
if (index > env->cpuid_level)
index = env->cpuid_level;
limit = env->cpuid_level;
}
if (index > limit) {
/* Intel documentation states that invalid EAX input will
* return the same information as EAX=cpuid_level
* (Intel SDM Vol. 2A - Instruction Set Reference - CPUID)
*/
index = env->cpuid_level;
}
switch(index) {