Re: [Qemu-devel] [kvm-unit-tests PATCH v13 1/4] arm: Define macros for accessing system registers

[Andrew Jones]

On Thu, Dec 01, 2016 at 09:59:03AM +0100, Andrew Jones wrote:
> 
> Should this be From: Andre?
> 
> On Wed, Nov 30, 2016 at 11:16:39PM -0600, Wei Huang wrote:
> > This patch defines four macros to assist creating system register
> > accessors under both ARMv7 and AArch64:
> >    * DEFINE_GET_SYSREG32(name, ...)
> >    * DEFINE_SET_SYSREG32(name, ...)
> >    * DEFINE_GET_SYSREG64(name, ...)
> >    * DEFINE_SET_SYSREG64(name, ...)
> > These macros are translated to inline functions with consistent naming,
> > get_##name() and set_##name(), which can be used by C code directly.
> > 
> > Signed-off-by: Andre Przywara <address@hidden>
> > Signed-off-by: Wei Huang <address@hidden>
> > ---
> >  lib/arm/asm/processor.h   | 37 ++++++++++++++++++++++++++++++++-----
> >  lib/arm64/asm/processor.h | 35 ++++++++++++++++++++++++++++-------
> >  2 files changed, 60 insertions(+), 12 deletions(-)
> > 
> > diff --git a/lib/arm/asm/processor.h b/lib/arm/asm/processor.h
> > index f25e7ee..3ca6b42 100644
> > --- a/lib/arm/asm/processor.h
> > +++ b/lib/arm/asm/processor.h
> > @@ -33,13 +33,40 @@ static inline unsigned long current_cpsr(void)
> >  
> >  #define current_mode() (current_cpsr() & MODE_MASK)
> >  
> > -static inline unsigned int get_mpidr(void)
> > -{
> > -   unsigned int mpidr;
> > -   asm volatile("mrc p15, 0, %0, c0, c0, 5" : "=r" (mpidr));
> > -   return mpidr;
> > +#define DEFINE_GET_SYSREG32(name, opc1, crn, crm, opc2)                    
> > \
> > +static inline uint32_t get_##name(void)                                    
> > \
> > +{                                                                  \
> > +   uint32_t reg;                                                   \
> > +   asm volatile("mrc p15, " #opc1 ", %0, " #crn ", " #crm ", "     \
> > +                #opc2 : "=r" (reg));                               \
> > +   return reg;                                                     \
> > +}
> > +
> > +#define DEFINE_SET_SYSREG32(name, opc1, crn, crm, opc2)                    
> > \
> > +static inline void set_##name(uint32_t value)                              
> > \
> > +{                                                                  \
> > +   asm volatile("mcr p15, " #opc1 ", %0, " #crn ", " #crm ", "     \
> > +                #opc2 :: "r" (value));                             \
>                            ^ nit: no space here, checkpatch would complain
> > +}
> > +
> > +#define DEFINE_GET_SYSREG64(name, opc, crm)                                
> > \
> > +static inline uint64_t get_##name(void)                                    
> > \
> > +{                                                                  \
> > +   uint32_t lo, hi;                                                \
> > +   asm volatile("mrrc p15, " #opc ", %0, %1, " #crm                \
> > +                : "=r" (lo), "=r" (hi));                           \
> > +   return (uint64_t)hi << 32 | lo;                                 \
> > +}
> > +
> > +#define DEFINE_SET_SYSREG64(name, opc, crm)                                
> > \
> > +static inline void set_##name(uint64_t value)                              
> > \
> > +{                                                                  \
> > +   asm volatile("mcrr p15, " #opc ", %0, %1, " #crm                \
> > +                :: "r" (value & 0xffffffff), "r" (value >> 32));   \
> >  }
> >  
> > +DEFINE_GET_SYSREG32(mpidr, 0, c0, c0, 5)
> > +
> >  /* Only support Aff0 for now, up to 4 cpus */
> >  #define mpidr_to_cpu(mpidr) ((int)((mpidr) & 0xff))
> >  
> > diff --git a/lib/arm64/asm/processor.h b/lib/arm64/asm/processor.h
> > index 84d5c7c..dfa75eb 100644
> > --- a/lib/arm64/asm/processor.h
> > +++ b/lib/arm64/asm/processor.h
> > @@ -66,14 +66,35 @@ static inline unsigned long current_level(void)
> >     return el & 0xc;
> >  }
> >  
> > -#define DEFINE_GET_SYSREG32(reg)                           \
> > -static inline unsigned int get_##reg(void)                 \
> > -{                                                          \
> > -   unsigned int reg;                                       \
> > -   asm volatile("mrs %0, " #reg "_el1" : "=r" (reg));      \
> > -   return reg;                                             \
> > +#define DEFINE_GET_SYSREG32(reg, el)                                       
> > \
> > +static inline uint32_t get_##reg(void)                                     
> > \
> > +{                                                                  \
> > +   uint32_t reg;                                                   \
> > +   asm volatile("mrs %0, " #reg "_" #el : "=r" (reg));             \
> > +   return reg;                                                     \
> >  }
> > -DEFINE_GET_SYSREG32(mpidr)
> > +
> > +#define DEFINE_SET_SYSREG32(reg, el)                                       
> > \
> > +static inline void set_##reg(uint32_t value)                               
> > \
> > +{                                                                  \
> > +   asm volatile("msr " #reg "_" #el ", %0" :: "r" (value));        \
> > +}

Another comment for arm64's SYSREG32 accessors. Technically there's no
32-bit register in AArch64, so the asm should always use an unsigned long
and explicit casts. That's what I did in [1].

> > +
> > +#define DEFINE_GET_SYSREG64(reg, el)                                       
> > \
> > +static inline uint64_t get_##reg(void)                                     
> > \
> > +{                                                                  \
> > +   uint64_t reg;                                                   \
> > +   asm volatile("mrs %0, " #reg "_" #el : "=r" (reg));             \
> > +   return reg;                                                     \
> > +}
> > +
> > +#define DEFINE_SET_SYSREG64(reg, el)                                       
> > \
> > +static inline void set_##reg(uint64_t value)                               
> > \
> > +{                                                                  \
> > +   asm volatile("msr " #reg "_" #el ", %0" :: "r" (value));        \
> > +}
> > +
> > +DEFINE_GET_SYSREG32(mpidr, el1)
> 
> 32-bit mpidr for arm64 isn't right, and it's changed by [1] in the
> gic series. However changing it to 64-bit with this patch would result
> in a get_mpidr() call that returns uint64_t on arm64 and uint32_t on
> arm32, which won't be nice for common code. Andre brought up during the
> review of [1] that we should be using the architectural types for register
> accessors. That means, that while internally all the above functions can
> know what's 32-bit and what's 64-bit, using uint32/64_t appropriately,
> the external interfaces should be 'unsigned long', 'unsigned int',
> 'unsigned long long'.
> 
> [1] 
> https://github.com/rhdrjones/kvm-unit-tests/commit/57e48b8e6dc2ddf4b2e4eb1ceb5a5f87f2dd074b
> 
> Thanks,
> drew
> 
> >  
> >  /* Only support Aff0 for now, gicv2 only */
> >  #define mpidr_to_cpu(mpidr) ((int)((mpidr) & 0xff))
> > -- 
> > 1.8.3.1
> > 
> > 
>