Re: [Xen-devel] [PATCH 14/16] x86/monitor: clarify separation between monitor subsys and vm-event as a whole

[Corneliu ZUZU <czuzu@xxxxxxxxxxxxxxx>]

On 7/9/2016 9:57 PM, Corneliu ZUZU wrote:
> On 7/9/2016 9:26 PM, Tamas K Lengyel wrote:
> > > diff --git a/xen/include/asm-x86/domain.h 
> > > b/xen/include/asm-x86/domain.h
> > > index ae1dcb4..7663da2 100644
> > > --- a/xen/include/asm-x86/domain.h
> > > +++ b/xen/include/asm-x86/domain.h
> > > @@ -9,6 +9,7 @@
> > >   #include <asm/e820.h>
> > >   #include <asm/mce.h>
> > >   #include <public/vcpu.h>
> > > +#include <public/vm_event.h>
> > >   #include <public/hvm/hvm_info_table.h>
> > >
> > >   #define has_32bit_shinfo(d) ((d)->arch.has_32bit_shinfo)
> > > @@ -503,6 +504,20 @@ typedef enum __packed {
> > >       SMAP_CHECK_DISABLED,        /* disable the check */
> > >   } smap_check_policy_t;
> > >
> > > +/*
> > > + * Should we emulate the next matching instruction on VCPU resume
> > > + * after a vm_event?
> > > + */
> > > +struct arch_vm_event_monitor {
> > This should be named struct arch_vcpu_monitor.
> Good idea.
>
> > > +    uint32_t emulate_flags;
> > > +    struct vm_event_emul_read_data emul_read_data;
> > This should probably get renamed as well at some point to struct
> > monitor_emul_read_data.
> Ack.
>
> > > +    struct monitor_write_data write_data;
> > > +};
> > > +
> > > +struct arch_vm_event {
> > > +    struct arch_vm_event_monitor *monitor;
> > > +};
> > IMHO there is not much point in defining struct arch_vm_event this
> > way, we could just as well store the pointer to the arch_monitor
> > directly in arch_vcpu as we do right now.
> I stated the reason for that in the commit message (see 3rd '*'), Jan 
> insists it would be preferable to occupy just one pointer in arch_vcpu 
> (which would still hold if we do as you suggest but I was wondering 
> how probable would it be in the future for one of the paging/share 
> vm-event subsystems to need per-vCPU resources). But personally, yeah, 
> I would have preferred what you suggest as well..
> Zuzu.
Tamas, any update on this? Do you think we should think now about 
per-vCPU resources being occupied in the future by paging/share or leave 
that for later and do what you suggested?
Thanks,
Corneliu.

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