Re: [PATCH 1/6] target/i386/kvm: Add feature bit definitions for KVM CPUID

[Chen, Zide]

On 4/26/2024 3:07 AM, Zhao Liu wrote:
> Add feature definiations for KVM_CPUID_FEATURES in CPUID (
> CPUID[4000_0001].EAX and CPUID[4000_0001].EDX), to get rid of lots of
> offset calculations.
> 
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> ---
> v2: Changed the prefix from CPUID_FEAT_KVM_* to CPUID_KVM_*. (Xiaoyao)
> ---
>  hw/i386/kvm/clock.c   |  5 ++---
>  target/i386/cpu.h     | 23 +++++++++++++++++++++++
>  target/i386/kvm/kvm.c | 28 ++++++++++++++--------------
>  3 files changed, 39 insertions(+), 17 deletions(-)
> 
> diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
> index 40aa9a32c32c..ce416c05a3d0 100644
> --- a/hw/i386/kvm/clock.c
> +++ b/hw/i386/kvm/clock.c
> @@ -27,7 +27,6 @@
>  #include "qapi/error.h"
>  
>  #include <linux/kvm.h>
> -#include "standard-headers/asm-x86/kvm_para.h"
>  #include "qom/object.h"
>  
>  #define TYPE_KVM_CLOCK "kvmclock"
> @@ -334,8 +333,8 @@ void kvmclock_create(bool create_always)
>  
>      assert(kvm_enabled());
>      if (create_always ||
> -        cpu->env.features[FEAT_KVM] & ((1ULL << KVM_FEATURE_CLOCKSOURCE) |
> -                                       (1ULL << KVM_FEATURE_CLOCKSOURCE2))) {
> +        cpu->env.features[FEAT_KVM] & (CPUID_KVM_CLOCK |
> +                                       CPUID_KVM_CLOCK2)) {

To achieve this purpose, how about doing the alternative to define an
API similar to KVM's guest_pv_has()?

xxxx_has() is simpler and clearer than "features[] & CPUID_xxxxx",
additionally, this helps to keep the definitions identical to KVM, more
readable and easier for future maintenance.