Re: [Xen-devel] [PATCH v5 5/9] monitor: ARM SMC events

[Julien Grall <julien.grall@xxxxxxx>]

Hello Tamas,

On 02/06/16 23:52, Tamas K Lengyel wrote:
> diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h
> index 9270d52..7976080 100644
> --- a/xen/include/public/vm_event.h
> +++ b/xen/include/public/vm_event.h
> @@ -119,6 +119,8 @@
>   #define VM_EVENT_REASON_SINGLESTEP              7
>   /* An event has been requested via HVMOP_guest_request_vm_event. */
>   #define VM_EVENT_REASON_GUEST_REQUEST           8
> +/* Privileged call executed (e.g. SMC) */
> +#define VM_EVENT_REASON_PRIVILEGED_CALL         9
>
>   /* Supported values for the vm_event_write_ctrlreg index. */
>   #define VM_EVENT_X86_CR0    0
> @@ -212,6 +214,13 @@ struct vm_event_mov_to_msr {
>       uint64_t value;
>   };
>
> +#define VM_EVENT_PRIVCALL_SMC   0
> +
> +struct vm_event_privcall {
> +    uint32_t type;
> +    uint32_t vector; /* ESR_EL2.ISS for SMC calls */
How do you expect the introspection app to deal with it? As explained in 
a previous mail [1], the ISS encoding is different between ARMv7 32-bit 
and ARMv8 32-bit. The former is unknown (see B3-1431 in ARM DDI 0406C.c) 
whilst the latter contains fields related to the condition (see D7-1897 
in ARM DDI 0406C.c).
This is because on ARMv8, the conditional SMC issued in AArch32 state 
may trap even if the condition has failed.
So the app would have to know whether the hypervisor is running on an 
ARMv7 or ARMv8 platform. But I am not aware of an easy way to 
differentiate it from the registers.
Furthermore, I think the vm_event app should only received SMCs whose 
condition has succeeded, because they will be actual SMC. The others 
should just be ignored.
IHMO, the vm_event should only contain the immediate. The rest only 
matters for the hypervisor.
Regards,

[1] 
http://lists.xenproject.org/archives/html/xen-devel/2016-06/msg00285.html
--
Julien Grall

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