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

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Fri, Jun 3, 2016 at 8:43 AM, Julien Grall <julien.grall@xxxxxxx> wrote:
> Hello Tamas,
>
> On 03/06/16 14:40, Tamas K Lengyel wrote:
>>
>>
>> On Jun 3, 2016 03:49, "Julien Grall" <julien.grall@xxxxxxx
>> <mailto:julien.grall@xxxxxxx>> wrote:
>>  >
>>  > 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..797608Burrington0 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.
>>
>> The app can certainly run other checks to determine what the CPU version
>> is, not being exclusively reliant on vm_event and running in a
>> privileged domain.
>
>
> Manufacturers are allowed to build their custom ARM processor based on the
> ARM ARM. The number of CPU version to check will likely be huge and you will
> not be future proof.
> `

If transmitting the ISS to the user this way is not enough in your
opinion I may just leave this item up for a future user to implement
as my use-case doesn't need it.

Tamas

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