Re: [Qemu-devel][PATCH v6 1/6] x86/cpu: Rename XSAVE related feature words.

[Yang Weijiang]

On Tue, Oct 13, 2020 at 05:08:54PM -0700, Sean Christopherson wrote:
> On Tue, Oct 13, 2020 at 01:19:30PM +0800, Yang Weijiang wrote:
> > With more components in XSS being developed on Intel platform,
> > it's necessary to clean up existing XSAVE related feature words to
> > make the name clearer. It's to prepare for adding CET related support
> > in following patches.
> > 
> > Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> > ---
> >  target/i386/cpu.c        | 60 ++++++++++++++++++++--------------------
> >  target/i386/cpu.h        |  6 ++--
> >  target/i386/fpu_helper.c |  2 +-
> >  target/i386/translate.c  |  2 +-
> >  4 files changed, 35 insertions(+), 35 deletions(-)
> > 
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index 588f32e136..e2891740f1 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -1050,7 +1050,7 @@ static FeatureWordInfo 
> > feature_word_info[FEATURE_WORDS] = {
> >          .tcg_features = 0,
> >          .unmigratable_flags = 0,
> >      },
> > -    [FEAT_XSAVE] = {
> > +    [FEAT_XSAVE_INSTRUCTION] = {
> 
> The COMP->XCRO change is great, but I don't think XSAVE->XSAVE_INSTRUCTION
> makes sense.  There is no guarantee the word will only be used for
> instructions; it already blurs the line, e.g. XSAVEC also changes the behavior
> of XRSTOR, and XSAVES also means the XSS MSR is available.
> 
> FWIW, I also don't find FEAT_XSAVE to be confusing.
>
Thanks for the feedback! I also found it's hard to rename it with a
precise one, just wanted to make all XSAVE related feature words more
specific. I'll revert it in next version.

> >          .type = CPUID_FEATURE_WORD,
> >          .feat_names = {
> >              "xsaveopt", "xsavec", "xgetbv1", "xsaves",
> > @@ -1084,7 +1084,7 @@ static FeatureWordInfo 
> > feature_word_info[FEATURE_WORDS] = {
> >          .cpuid = { .eax = 6, .reg = R_EAX, },
> >          .tcg_features = TCG_6_EAX_FEATURES,
> >      },
> > -    [FEAT_XSAVE_COMP_LO] = {
> > +    [FEAT_XSAVE_XCR0_LO] = {
> >          .type = CPUID_FEATURE_WORD,
> >          .cpuid = {
> >              .eax = 0xD,