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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.06.16 at 09:08, <czuzu@xxxxxxxxxxxxxxx> wrote:
> On 6/17/2016 11:25 AM, Corneliu ZUZU wrote:
>> On 6/16/2016 6:16 PM, Jan Beulich wrote:
>>>>>> On 16.06.16 at 16:12, <czuzu@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
>>>> ---
>>>>   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? 

I don't really care about the specifics, my only request is what I
already voiced: Common code should not access arch-specific
fields. Having the field to hold the control register bits common,
but the definitions for the individual bits arch-specific is perfectly
fine for this (assuming that these per-arch definitions then again
don't get used in common code).

Jan


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