Re: [libvirt] [Qemu-devel] [PATCH qom-cpu 5/9] target-i386: Add ECX information to FeatureWordInfo
On Fri, May 03, 2013 at 05:16:46PM +0200, Andreas Färber wrote:
Am 22.04.2013 21:00, schrieb Eduardo Habkost:
> FEAT_7_0_EBX uses ECX as input, so we have to take that into account
> when reporting feature word values.
>
> Signed-off-by: Eduardo Habkost <ehabkost(a)redhat.com>
> ---
> target-i386/cpu.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 110ef98..314931e 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -151,8 +151,10 @@ static const char *cpuid_7_0_ebx_feature_name[] = {
>
> typedef struct FeatureWordInfo {
> const char **feat_names;
> - uint32_t cpuid_eax; /* Input EAX for CPUID */
> - int cpuid_reg; /* R_* register constant */
> + uint32_t cpuid_eax; /* Input EAX for CPUID */
> + bool cpuid_needs_ecx; /* CPUID instruction uses ECX as input */
Why do we need this needs_ field here? eax and reg just seem to be
reindented and the comment reworded for reg.
We need it so we know if ECX is used as input on that CPUID leaf, in
other words: so we know if "cpuid-input-ecx" needs to be set on
X86CPUFeatureWordInfo or not.
"cpuid-input-ecx" is optional because most CPUID leafs don't depend on
input ECX value, only EAX. cpuid_needs_ecx has a similar meaning to
KVM_CPUID_FLAG_SIGNIFCANT_INDEX on kvm_cpuid_entry2.flags.
It just seems to be passed through to has_cpuid_input_ecx, which I
neither see defined nor checked - that data structure already existed
elsewhere as such?
X86CPUFeatureWordInfo is generated from the QAPI schema.
Andreas
> + uint32_t cpuid_ecx; /* Input ECX value for CPUID */
> + int cpuid_reg; /* output register (R_* constant) */
> } FeatureWordInfo;
>
> static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
> @@ -186,7 +188,9 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
> },
> [FEAT_7_0_EBX] = {
> .feat_names = cpuid_7_0_ebx_feature_name,
> - .cpuid_eax = 7, .cpuid_reg = R_EBX,
> + .cpuid_eax = 7,
> + .cpuid_needs_ecx = true, .cpuid_ecx = 0,
> + .cpuid_reg = R_EBX,
> },
> };
>
>
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--
Eduardo