Re: run time memory trap question

[Andrii Tseglytskyi <andrii.tseglytskyi@globallogic.com>]

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Hi Julien,


> >
> >     > Can anyone clarify - is it possible to make a run time memory trap
> in
> >     > Xen hypervisor?
> >
> >     I guess you are talking about ARM? If so, it's not possible right
> now.
> >
> >
> > Does it mean, that it is possible on x86 ?
>
> Yes, you can look at register_io_handler in xen/arch/x86/hvm/intercept.c
>
> It's used a static array, but I don't think this is the solution for
> ARM. We don't know in advance the maximum number of MMIO region to handle.
>
>
What I'm thinking about for ARM - is to use linked list for MMIO handlers +
API to register / unregister handler.

xen/arch/arm/io.c:

 25 static const struct mmio_handler *const mmio_handlers[] =
 26 {
 27     &vgic_distr_mmio_handler,
 28     &vuart_mmio_handler,
 29 };

This can be changed to list. New API will add / remove entries. VGIC and
VUART will call something like
mmio_register_handler(&vgic_distr_mmio_handle) during corresponding
initcall.

Than the only change which is required for existing int
handle_mmio(mmio_info_t *info) function  - is to enumerate list, instead of
array
 32 int handle_mmio(mmio_info_t *info)
 33 {
 34     struct vcpu *v = current;
 35     int i;
 36
 37     for ( i = 0; i < MMIO_HANDLER_NR; i++ ) --> *list_for_each*
 38         if ( mmio_handlers[i]->check_handler(v, info->gpa) )
 39             return info->dabt.write ?
 40                 mmio_handlers[i]->write_handler(v, info) :
 41                 mmio_handlers[i]->read_handler(v, info);
 42
 43     return 0;
 44 }

Something like this.

Regards,
Andrii



> --
> Julien Grall
>



-- 

Andrii Tseglytskyi | Embedded Dev
GlobalLogic
www.globallogic.com

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