On Tue, Apr 20, 2021 at 06:08:50PM -0700, Sean Christopherson wrote:
> Take "enum kvm_only_cpuid_leafs" in scattered specific CPUID helpers
> (which is obvious in hindsight), and use "unsigned int" for leafs that
> can be the kernel's standard "enum cpuid_leaf" or the aforementioned
> KVM-only variant. Loss of the enum params is a bit disapponting, but
> gcc obviously isn't providing any extra sanity checks, and the various
Unfortunately, gcc's -Wenum-conversion is behind -Wextra rather than
-Wall like clang. If you explicitly enable it with
KCFLAGS=-Wenum-conversion to your make invocation, it will warn in the
exact same way as clang:
arch/x86/kvm/cpuid.c: In function 'kvm_set_cpu_caps':
arch/x86/kvm/cpuid.c:499:29: warning: implicit conversion from 'enum kvm_only_cpuid_leafs' to 'enum cpuid_leafs' [-Wenum-conversion]
499 | kvm_cpu_cap_init_scattered(CPUID_12_EAX,
| ^~~~~~~~~~~~
arch/x86/kvm/cpuid.c: In function '__do_cpuid_func':
arch/x86/kvm/cpuid.c:837:31: warning: implicit conversion from 'enum kvm_only_cpuid_leafs' to 'enum cpuid_leafs' [-Wenum-conversion]
837 | cpuid_entry_override(entry, CPUID_12_EAX);
| ^~~~~~~~~~~~
clang's warning for comparison/posterity:
arch/x86/kvm/cpuid.c:499:29: warning: implicit conversion from enumeration type 'enum kvm_only_cpuid_leafs' to different enumeration type 'enum cpuid_leafs' [-Wenum-conversion]
kvm_cpu_cap_init_scattered(CPUID_12_EAX,
~~~~~~~~~~~~~~~~~~~~~~~~~~ ^~~~~~~~~~~~
arch/x86/kvm/cpuid.c:837:31: warning: implicit conversion from enumeration type 'enum kvm_only_cpuid_leafs' to different enumeration type 'enum cpuid_leafs' [-Wenum-conversion]
cpuid_entry_override(entry, CPUID_12_EAX);
~~~~~~~~~~~~~~~~~~~~ ^~~~~~~~~~~~
2 warnings generated.
> BUILD_BUG_ON() assertions ensure the input is in range.
>
> This fixes implicit enum conversions that are detected by clang-11.
>
> Fixes: 4e66c0cb79b7 ("KVM: x86: Add support for reverse CPUID lookup of scattered features")
> Cc: Kai Huang <kai.huang@xxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
This makes GCC and clang happy in my brief testing.
I assume this will get squashed but in case not, here are some tags:
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> ---
>
> Hopefully it's not too late to squash this...
>
> arch/x86/kvm/cpuid.c | 5 +++--
> arch/x86/kvm/cpuid.h | 2 +-
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 96e41e1a1bde..e9d644147bf5 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -365,7 +365,7 @@ int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
> }
>
> /* Mask kvm_cpu_caps for @leaf with the raw CPUID capabilities of this CPU. */
> -static __always_inline void __kvm_cpu_cap_mask(enum cpuid_leafs leaf)
> +static __always_inline void __kvm_cpu_cap_mask(unsigned int leaf)
> {
> const struct cpuid_reg cpuid = x86_feature_cpuid(leaf * 32);
> struct kvm_cpuid_entry2 entry;
> @@ -378,7 +378,8 @@ static __always_inline void __kvm_cpu_cap_mask(enum cpuid_leafs leaf)
> kvm_cpu_caps[leaf] &= *__cpuid_entry_get_reg(&entry, cpuid.reg);
> }
>
> -static __always_inline void kvm_cpu_cap_init_scattered(enum cpuid_leafs leaf, u32 mask)
> +static __always_inline
> +void kvm_cpu_cap_init_scattered(enum kvm_only_cpuid_leafs leaf, u32 mask)
> {
> /* Use kvm_cpu_cap_mask for non-scattered leafs. */
> BUILD_BUG_ON(leaf < NCAPINTS);
> diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
> index eeb4a3020e1b..7bb4504a2944 100644
> --- a/arch/x86/kvm/cpuid.h
> +++ b/arch/x86/kvm/cpuid.h
> @@ -236,7 +236,7 @@ static __always_inline void cpuid_entry_change(struct kvm_cpuid_entry2 *entry,
> }
>
> static __always_inline void cpuid_entry_override(struct kvm_cpuid_entry2 *entry,
> - enum cpuid_leafs leaf)
> + unsigned int leaf)
> {
> u32 *reg = cpuid_entry_get_reg(entry, leaf * 32);
>
> --
> 2.31.1.368.gbe11c130af-goog
>
