Re: [PATCH 6/7] vm-event/arm: move hvm_event_cr->common vm_event_monitor_cr

[Corneliu ZUZU <czuzu@bitdefender.com>]

On 6/16/2016 6:16 PM, Jan Beulich wrote:
>>>> On 16.06.16 at 16:12, <czuzu@bitdefender.com> wrote:
>> Prepare for ARM implementation of control-register write vm-events by moving
>> X86-specific hvm_event_cr to the common-side.
>>
>> Signed-off-by: Corneliu ZUZU <czuzu@bitdefender.com>
>> ---
>>   xen/arch/x86/hvm/event.c        | 30 ------------------------------
>>   xen/arch/x86/hvm/hvm.c          |  2 +-
>>   xen/arch/x86/monitor.c          | 37 -------------------------------------
>>   xen/arch/x86/vm_event.c         |  2 +-
>>   xen/common/monitor.c            | 40 ++++++++++++++++++++++++++++++++++++++++
>>   xen/common/vm_event.c           | 31 +++++++++++++++++++++++++++++++
>>   xen/include/asm-x86/hvm/event.h | 13 ++++---------
>>   xen/include/asm-x86/monitor.h   |  2 --
>>   xen/include/xen/monitor.h       |  4 ++++
>>   xen/include/xen/vm_event.h      | 10 ++++++++++
>>   10 files changed, 91 insertions(+), 80 deletions(-)
> Considering that there's no ARM file getting altered here at all,
> mentioning ARM in the subject is a little odd.

This patch and the following one should be meld together.
I only split them to ease reviewing, sorry I forgot to mention that in 
the cover letter.

>
>> --- a/xen/common/monitor.c
>> +++ b/xen/common/monitor.c
>> @@ -62,6 +62,46 @@ int monitor_domctl(struct domain *d, struct xen_domctl_monitor_op *mop)
>>   
>>       switch ( mop->event )
>>       {
>> +#if CONFIG_X86
> #ifdef please.
Ack.
>> +    case XEN_DOMCTL_MONITOR_EVENT_WRITE_CTRLREG:
>> +    {
>> +        struct arch_domain *ad = &d->arch;
> Peeking into the next patch I see that this stays there. Common code,
> however, shouldn't access ->arch sub-structures - respective fields
> should be moved out.

Then we need to find a resolution that avoids code duplication.
The code is the same, but those bits that are currently on the arch side 
(arch.monitor.write_ctrlreg_*) cannot be moved to common as they are, 
since their -number- might differ from arch-to-arch.
But we could:
- in public/vm_event.h, besides the VM_EVENT_X86_* and VM_EVENT_ARM_* 
defines (wcr index), also have
     #define VM_EVENT_X86_CR_COUNT        4
     #define VM_EVENT_ARM_CR_COUNT      4
- move the 3 write_ctrlreg_{enabled,sync,onchangeonly} fields from 
arch_domain to domain (common) and make them 8-bits wide each for now 
(widened more in the future if the need arises)
- let monitor_ctrlreg_bitmask() macro to be architecture-dependent and 
use the introduced VM_EVENT_<arch>_CR_COUNT

Tamas, we also talked on this matter @ some point (when I sent the 
patches that moved vm-event parts to common). What do you think of the 
above?

>
> And looking at all the uses of this variable I get the impression that
> you really want a shorthand for &d->arch.monitor (if any such
> helper variable is worthwhile to have here in the first place).

Well, this was a simple cut-paste operation, not very old content aware :)
Personally I prefer the current shorthand (ad) (seems more intuitive and 
is consistent with the other XEN_DOMCTL_MONITOR_EVENT_* cases), but if 
you prefer I'll change that shorthand to am = &d->arch.monitor?

>> --- a/xen/include/asm-x86/monitor.h
>> +++ b/xen/include/asm-x86/monitor.h
>> @@ -24,8 +24,6 @@
>>   
>>   #include <xen/sched.h>
>>   
>> -#define monitor_ctrlreg_bitmask(ctrlreg_index) (1U << (ctrlreg_index))
>> -
>>   static inline
>>   int arch_monitor_domctl_op(struct domain *d, struct xen_domctl_monitor_op *mop)
>>   {
>> --- a/xen/include/xen/monitor.h
>> +++ b/xen/include/xen/monitor.h
>> @@ -25,6 +25,10 @@
>>   struct domain;
>>   struct xen_domctl_monitor_op;
>>   
>> +#if CONFIG_X86
>> +#define monitor_ctrlreg_bitmask(ctrlreg_index) (1U << (ctrlreg_index))
>> +#endif
> What's the point in removing this from the x86 header if then it
> needs to be put in such a conditional? If the conditional gets
> dropped in the next patch, then I think you have two options:
> Leave it where it is here, and move it there. Or move it here,
> but omit the conditional right away - I can't see this definition
> being present to harm the ARM build in any way.

Meld comment above.

>
>> --- a/xen/include/xen/vm_event.h
>> +++ b/xen/include/xen/vm_event.h
>> @@ -96,6 +96,16 @@ void vm_event_vcpu_unpause(struct vcpu *v);
>>   int vm_event_monitor_traps(struct vcpu *v, uint8_t sync,
>>                              vm_event_request_t *req);
>>   
>> +#if CONFIG_X86
>> +/*
>> + * Called for the current vCPU on control-register changes by guest.
>> + * The event might not fire if the client has subscribed to it in onchangeonly
>> + * mode, hence the bool_t return type for control register write events.
>> + */
>> +bool_t vm_event_monitor_cr(unsigned int index, unsigned long value,
>> +                           unsigned long old);
>> +#endif
> Same goes for the declaration here.
>
> Jan
>
>

Meld comment above.

Corneliu.

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