[PATCH 1/2] kvm/arm64: Rename HSR to ESR

[Mark Rutland]

On Mon, Jun 29, 2020 at 07:18:40PM +1000, Gavin Shan wrote:
> kvm/arm32 isn't supported since commit 541ad0150ca4 ("arm: Remove
> 32bit KVM host support"). So HSR isn't meaningful since then. This
> renames HSR to ESR accordingly. This shouldn't cause any functional
> changes:
> 
>    * Rename kvm_vcpu_get_hsr() to kvm_vcpu_get_esr() to make the
>      function names self-explanatory.
>    * Rename variables from @hsr to @esr to make them self-explanatory.
> 
> Signed-off-by: Gavin Shan <gshan at redhat.com>

At a high-level, I agree that we should move to the `esr` naming to
match the architecture and minimize surprise. However, I think there are
some ABI changes here, which *are* funcitonal changes, and those need to
be avoided.

[...]

> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index ba85bb23f060..d54345573a88 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -140,7 +140,7 @@ struct kvm_guest_debug_arch {
>  };
>  
>  struct kvm_debug_exit_arch {
> -	__u32 hsr;
> +	__u32 esr;
>  	__u64 far;	/* used for watchpoints */
>  };

This is userspace ABI, and changing this *will* break userspace. This
*is* a functional change.

NAK to this specifically. At best these should be a comment here that
this is naming is legacym but must stay for ABI reasons.

[...]

> diff --git a/arch/arm64/kvm/trace_arm.h b/arch/arm64/kvm/trace_arm.h
> index 4c71270cc097..ee4f691b16ff 100644
> --- a/arch/arm64/kvm/trace_arm.h
> +++ b/arch/arm64/kvm/trace_arm.h
> @@ -42,7 +42,7 @@ TRACE_EVENT(kvm_exit,
>  		__entry->vcpu_pc		= vcpu_pc;
>  	),
>  
> -	TP_printk("%s: HSR_EC: 0x%04x (%s), PC: 0x%08lx",
> +	TP_printk("%s: ESR_EC: 0x%04x (%s), PC: 0x%08lx",
>  		  __print_symbolic(__entry->ret, kvm_arm_exception_type),
>  		  __entry->esr_ec,
>  		  __print_symbolic(__entry->esr_ec, kvm_arm_exception_class),

Likewise, isn't all the tracepoint format stuff ABI? I'm not comfortable
that we can change this.

Thanks,
Mark.

> @@ -50,27 +50,27 @@ TRACE_EVENT(kvm_exit,
>  );
>  
>  TRACE_EVENT(kvm_guest_fault,
> -	TP_PROTO(unsigned long vcpu_pc, unsigned long hsr,
> +	TP_PROTO(unsigned long vcpu_pc, unsigned long esr,
>  		 unsigned long hxfar,
>  		 unsigned long long ipa),
> -	TP_ARGS(vcpu_pc, hsr, hxfar, ipa),
> +	TP_ARGS(vcpu_pc, esr, hxfar, ipa),
>  
>  	TP_STRUCT__entry(
>  		__field(	unsigned long,	vcpu_pc		)
> -		__field(	unsigned long,	hsr		)
> +		__field(	unsigned long,	esr		)
>  		__field(	unsigned long,	hxfar		)
>  		__field(   unsigned long long,	ipa		)
>  	),
>  
>  	TP_fast_assign(
>  		__entry->vcpu_pc		= vcpu_pc;
> -		__entry->hsr			= hsr;
> +		__entry->esr			= esr;
>  		__entry->hxfar			= hxfar;
>  		__entry->ipa			= ipa;
>  	),
>  
> -	TP_printk("ipa %#llx, hsr %#08lx, hxfar %#08lx, pc %#08lx",
> -		  __entry->ipa, __entry->hsr,
> +	TP_printk("ipa %#llx, esr %#08lx, hxfar %#08lx, pc %#08lx",
> +		  __entry->ipa, __entry->esr,
>  		  __entry->hxfar, __entry->vcpu_pc)
>  );
>  
> diff --git a/arch/arm64/kvm/trace_handle_exit.h b/arch/arm64/kvm/trace_handle_exit.h
> index 2c56d1e0f5bd..94ef1a98e609 100644
> --- a/arch/arm64/kvm/trace_handle_exit.h
> +++ b/arch/arm64/kvm/trace_handle_exit.h
> @@ -139,18 +139,18 @@ TRACE_EVENT(trap_reg,
>  );
>  
>  TRACE_EVENT(kvm_handle_sys_reg,
> -	TP_PROTO(unsigned long hsr),
> -	TP_ARGS(hsr),
> +	TP_PROTO(unsigned long esr),
> +	TP_ARGS(esr),
>  
>  	TP_STRUCT__entry(
> -		__field(unsigned long,	hsr)
> +		__field(unsigned long,	esr)
>  	),
>  
>  	TP_fast_assign(
> -		__entry->hsr = hsr;
> +		__entry->esr = esr;
>  	),
>  
> -	TP_printk("HSR 0x%08lx", __entry->hsr)
> +	TP_printk("ESR 0x%08lx", __entry->esr)
>  );
>  
>  TRACE_EVENT(kvm_sys_access,
> -- 
> 2.23.0
>