On Tue, May 09, 2017 at 12:20:33PM +0100, Daniel P. Berrange wrote:
> Change the nested if statements into a flat format, to make
> it clearer what validation / capping is being performed on
> different CPUID index values.
>
> Signed-off-by: Daniel P. Berrange <berra...@redhat.com>
Probably worth noting in the commit message that the patch
changes the results of cpu_x86_cpuid() when
(index > env->cpuid_xlevel2), and that it won't have any
guest-visible effect because no CPUID[0xC0000001] feature is
supported by TCG, and KVM code will never call cpu_x86_cpuid()
with (index > env->cpuid_xlevel2).
Reviewed-by: Eduardo Habkost <ehabk...@redhat.com>
> ---
> target/i386/cpu.c | 35 +++++++++++++++--------------------
> 1 file changed, 15 insertions(+), 20 deletions(-)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 13c0985..8cb4af4 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -2626,28 +2626,23 @@ 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) {
> --
> 2.9.3
>
--
Eduardo
