Re: [PATCH 05/16] arm64: Add flags to check the safety of a capability for late CPU

[Suzuki K Poulose]

On 30/01/18 14:56, Dave Martin wrote:
> On Tue, Jan 30, 2018 at 11:17:38AM +0000, Suzuki K Poulose wrote:
> > On 26/01/18 10:10, Dave Martin wrote:
> > > On Tue, Jan 23, 2018 at 12:27:58PM +0000, Suzuki K Poulose wrote:
> > > > Add two different flags to indicate if the conflict of a capability
> > > > on a late CPU with the current system state
> > > >
> > > >   1) Can a CPU have a capability when the system doesn't have it ?
> > > >
> > > >      Most arm64 features could have this set. While erratum work arounds
> > > >      cannot have this, as we may miss work arounds.
> > > >
> > > >   2) Can a CPU miss a capability when the system has it ?
> > > >      This could be set for arm64 erratum work arounds as we don't
> > > >      care if a CPU doesn't need the work around. However it should
> > > >      be clear for features.
> > > >
> > > > These flags could be added to certain entries based on their nature.
> > > >
> > > > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > > > ---
> > > >   arch/arm64/include/asm/cpufeature.h | 35 +++++++++++++++++++++++++++++++----
> > > >   1 file changed, 31 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> > > > index 4fd5de8ef33e..27d037bb0451 100644
> > > > --- a/arch/arm64/include/asm/cpufeature.h
> > > > +++ b/arch/arm64/include/asm/cpufeature.h
> > > > @@ -94,10 +94,25 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
> > > >   #define SCOPE_SYSTEM				ARM64_CPUCAP_SCOPE_SYSTEM
> > > >   #define SCOPE_LOCAL_CPU				ARM64_CPUCAP_SCOPE_LOCAL_CPU
> > > > -/* CPU errata detected at boot time based on feature of one or more CPUs */
> > > > -#define ARM64_CPUCAP_STRICT_CPU_LOCAL_ERRATUM	(ARM64_CPUCAP_SCOPE_LOCAL_CPU)
> > > > -/* CPU feature detected at boot time based on system-wide value of a feature */
> > > > -#define ARM64_CPUCAP_BOOT_SYSTEM_FEATURE	(ARM64_CPUCAP_SCOPE_SYSTEM)
> > > > +/* Is it safe for a late CPU to have this capability when system doesn't already have */
> > > > +#define ARM64_CPUCAP_LATE_CPU_SAFE_TO_HAVE	BIT(2)
> > > > +/* Is it safe for a late CPU to miss this capability when system has it */
> > > > +#define ARM64_CPUCAP_LATE_CPU_SAFE_TO_MISS	BIT(3)
> > >
> > > Maybe _OPTIONAL and _PERMITTED would be a bit less verbose?
> > >
> > > Alternatively,
> > > 	ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU
> > > 	ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU
> >
> > Sounds better than what I have. I have picked them up.
>
> Cool, I had resigned myself to probably not winning that one ;)

Well, you have won almost all in this series :-)

Cheers
Suzuki