Re: [PATCH v2] xen/arm64: Remove READ/WRITE_SYSREG32 helper macros

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Michal,

> On 9 Jul 2021, at 13:40, Michal Orzel <Michal.Orzel@xxxxxxx> wrote:
> 
> AArch64 system registers are 64bit whereas AArch32 ones
> are 32bit or 64bit. MSR/MRS are expecting 64bit values thus
> we should get rid of helpers READ/WRITE_SYSREG32
> in favour of using READ/WRITE_SYSREG.
> 
> The last place in code making use of READ/WRITE_SYSREG32
> on arm64 is in TVM_REG macro defining functions vreg_emulate_<register>.
> Implement a macro WRITE_SYSREG_SZ which expands as follows:
> -on arm64: WRITE_SYSREG
> -on arm32: WRITE_SYSREG{32/64}
> 
> As there are no other places in the code using these helpers
> on arm64 - remove them.
> 
> Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> ---
> Changes since v1:
> -implement WRITE_SYSREG_SZ instead of duplicating the TVM_REG
> ---
> xen/arch/arm/vcpreg.c               | 12 +++++++++++-
> xen/include/asm-arm/arm64/sysregs.h |  4 ----
> 2 files changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/arm/vcpreg.c b/xen/arch/arm/vcpreg.c
> index f0cdcc8a54..10c4846954 100644
> --- a/xen/arch/arm/vcpreg.c
> +++ b/xen/arch/arm/vcpreg.c
> @@ -47,6 +47,16 @@
>  *
>  */
> 
> +#ifdef CONFIG_ARM_64
> +#define WRITE_SYSREG_SZ(sz, val, sysreg)     WRITE_SYSREG(val, sysreg)
> +#else
> +/*
> + * WRITE_SYSREG{32/64} on arm32 is defined as variadic macro which imposes
> + * on the below macro to be defined like that as well.
> + */
> +#define WRITE_SYSREG_SZ(sz, val, sysreg...)  WRITE_SYSREG##sz(val, sysreg)
> +#endif
> +
> /* The name is passed from the upper macro to workaround macro expansion. */
> #define TVM_REG(sz, func, reg...)                                           \
> static bool func(struct cpu_user_regs *regs, uint##sz##_t *r, bool read)    \
> @@ -55,7 +65,7 @@ static bool func(struct cpu_user_regs *regs, uint##sz##_t 
> *r, bool read)    \
>     bool cache_enabled = vcpu_has_cache_enabled(v);                         \
>                                                                             \
>     GUEST_BUG_ON(read);                                                     \
> -    WRITE_SYSREG##sz(*r, reg);                                              \
> +    WRITE_SYSREG_SZ(sz, *r, reg);                                           \
>                                                                             \
>     p2m_toggle_cache(v, cache_enabled);                                     \
>                                                                             \
> diff --git a/xen/include/asm-arm/arm64/sysregs.h 
> b/xen/include/asm-arm/arm64/sysregs.h
> index 077fd95fb7..795901e1ba 100644
> --- a/xen/include/asm-arm/arm64/sysregs.h
> +++ b/xen/include/asm-arm/arm64/sysregs.h
> @@ -87,10 +87,6 @@
> 
> /* Access to system registers */
> 
> -#define READ_SYSREG32(name) ((uint32_t)READ_SYSREG64(name))
> -
> -#define WRITE_SYSREG32(v, name) WRITE_SYSREG64((uint64_t)v, name)
> -
> #define WRITE_SYSREG64(v, name) do {                    \
>     uint64_t _r = v;                                    \
>     asm volatile("msr "__stringify(name)", %0" : : "r" (_r));       \
> -- 
> 2.29.0
> 
>