Re: [Xen-devel] [RFC PATCH v1 02/10] xen/arm: register mmio handler at runtime

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hello Vijay,

(Adding Andrii who is working on a similar patch).

Thanks you for the patch.

On 03/19/2014 02:17 PM, vijay.kilari@xxxxxxxxx wrote:
> From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
> 
> mmio handlers are registers at compile time
> for drivers like vuart and vgic.
> Make mmio handler registered at runtime by
> creating linked list of mmio handlers
> 
> Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
> ---
>  xen/arch/arm/io.c    |   32 +++++++++++++++++---------
>  xen/arch/arm/io.h    |   16 +++++--------
>  xen/arch/arm/vgic.c  |   61 
> ++++++++++++++++++++++++++------------------------
>  xen/arch/arm/vuart.c |   39 ++++++++++++++++----------------
>  4 files changed, 79 insertions(+), 69 deletions(-)
> 
> diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
> index a6db00b..d140b29 100644
> --- a/xen/arch/arm/io.c
> +++ b/xen/arch/arm/io.c
> @@ -17,31 +17,41 @@
>   */
>  
>  #include <xen/config.h>
> +#include <xen/init.h>
> +#include <xen/kernel.h>
>  #include <xen/lib.h>
> +#include <xen/spinlock.h>
>  #include <asm/current.h>
>  
>  #include "io.h"
>  
> -static const struct mmio_handler *const mmio_handlers[] =
> -{
> -    &vgic_distr_mmio_handler,
> -    &vuart_mmio_handler,
> -};
> -#define MMIO_HANDLER_NR ARRAY_SIZE(mmio_handlers)
> +LIST_HEAD(handle_head);
> +static DEFINE_SPINLOCK(handler_lock);

As you change the code, I would prefer a per domain list IO handler. So
we can easily handle GICv2 guest on GICv3 host.

This list would only contains handlers that will be effectively used for
the domain.

>  int handle_mmio(mmio_info_t *info)
>  {
>      struct vcpu *v = current;
> -    int i;
> +    struct list_head *pos;
> +    struct mmio_handler *mmio_handle;
>  
> -    for ( i = 0; i < MMIO_HANDLER_NR; i++ )
> -        if ( mmio_handlers[i]->check_handler(v, info->gpa) )
> +    list_for_each(pos, &handle_head) {
> +        mmio_handle = list_entry(pos, struct mmio_handler, handle_list);

You can use list_for_each_entry here.

> +        if ( mmio_handle->check_handler(v, info->gpa) )
>              return info->dabt.write ?
> -                mmio_handlers[i]->write_handler(v, info) :
> -                mmio_handlers[i]->read_handler(v, info);
> +                mmio_handle->write_handler(v, info) :
> +                mmio_handle->read_handler(v, info);
> +    }
>  
>      return 0;
>  }
> +
> +void register_mmio_handler(struct mmio_handler * handle)
> +{
> +    spin_lock(&handler_lock);

Why do you take the lock here and not in handle_mmio?

> +    list_add(&handle->handle_list, &handle_head);
> +    spin_unlock(&handler_lock);
> +}
> +
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/xen/arch/arm/io.h b/xen/arch/arm/io.h
> index 8d252c0..99cd7c3 100644
> --- a/xen/arch/arm/io.h
> +++ b/xen/arch/arm/io.h
> @@ -22,6 +22,7 @@
>  #include <xen/lib.h>
>  #include <asm/processor.h>
>  #include <asm/regs.h>
> +#include <xen/list.h>
>  
>  typedef struct
>  {
> @@ -30,20 +31,15 @@ typedef struct
>      paddr_t gpa;
>  } mmio_info_t;
>  
> -typedef int (*mmio_read_t)(struct vcpu *v, mmio_info_t *info);
> -typedef int (*mmio_write_t)(struct vcpu *v, mmio_info_t *info);
> -typedef int (*mmio_check_t)(struct vcpu *v, paddr_t addr);
> -

Why did you remove the typedef? It was useful for the code comprehension.

>  struct mmio_handler {
> -    mmio_check_t check_handler;
> -    mmio_read_t read_handler;
> -    mmio_write_t write_handler;
> +    int (*read_handler)(struct vcpu *v, mmio_info_t *info);
> +    int (*write_handler)(struct vcpu *v, mmio_info_t *info);
> +    int (*check_handler)(struct vcpu *v, paddr_t addr);

If we are going to a per domain list IO, I would remove check_handler
and replacing by:

paddr_t addr;
paddr_t size;

> +    struct list_head handle_list;

On a previous mail (see
http://www.gossamer-threads.com/lists/xen/devel/317457#317457) I said
that a list would be better ... but after thinking we can define a fixed
array of 16 cells. It would be enough for now.

You can see an example in arch/x86/hvm/intercept.c

>  };
>  
> -extern const struct mmio_handler vgic_distr_mmio_handler;
> -extern const struct mmio_handler vuart_mmio_handler;
> -
>  extern int handle_mmio(mmio_info_t *info);
> +void register_mmio_handler(struct mmio_handler * handle);
>  
>  #endif
>  
> diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
> index 553411d..d2a13fb 100644
> --- a/xen/arch/arm/vgic.c
> +++ b/xen/arch/arm/vgic.c
> @@ -73,34 +73,6 @@ static struct vgic_irq_rank *vgic_irq_rank(struct vcpu *v, 
> int b, int n)
>          return NULL;
>  }
>  
> -int domain_vgic_init(struct domain *d)
> -{
> -    int i;
> -
> -    d->arch.vgic.ctlr = 0;
> -
> -    /* Currently nr_lines in vgic and gic doesn't have the same meanings
> -     * Here nr_lines = number of SPIs
> -     */
> -    if ( d->domain_id == 0 )
> -        d->arch.vgic.nr_lines = gic_number_lines() - 32;
> -    else
> -        d->arch.vgic.nr_lines = 0; /* We don't need SPIs for the guest */
> -
> -    d->arch.vgic.shared_irqs =
> -        xzalloc_array(struct vgic_irq_rank, DOMAIN_NR_RANKS(d));
> -    d->arch.vgic.pending_irqs =
> -        xzalloc_array(struct pending_irq, d->arch.vgic.nr_lines);
> -    for (i=0; i<d->arch.vgic.nr_lines; i++)
> -    {
> -        INIT_LIST_HEAD(&d->arch.vgic.pending_irqs[i].inflight);
> -        INIT_LIST_HEAD(&d->arch.vgic.pending_irqs[i].lr_queue);
> -    }
> -    for (i=0; i<DOMAIN_NR_RANKS(d); i++)
> -        spin_lock_init(&d->arch.vgic.shared_irqs[i].lock);
> -    return 0;
> -}
> -

I would predefine vgic_distr_mmio_handler early rather moving the whole
function. It's easier to understand the modification in this patch.

[..]

>  struct pending_irq *irq_to_pending(struct vcpu *v, unsigned int irq)
>  {
>      struct pending_irq *n;
> diff --git a/xen/arch/arm/vuart.c b/xen/arch/arm/vuart.c
> index b9d3ced..c237d71 100644
> --- a/xen/arch/arm/vuart.c
> +++ b/xen/arch/arm/vuart.c
> @@ -44,24 +44,6 @@
>  
>  #define domain_has_vuart(d) ((d)->arch.vuart.info != NULL)
>  
> -int domain_vuart_init(struct domain *d)
> -{
> -    ASSERT( !d->domain_id );
> -
> -    d->arch.vuart.info = serial_vuart_info(SERHND_DTUART);
> -    if ( !d->arch.vuart.info )
> -        return 0;
> -
> -    spin_lock_init(&d->arch.vuart.lock);
> -    d->arch.vuart.idx = 0;
> -
> -    d->arch.vuart.buf = xzalloc_array(char, VUART_BUF_SIZE);
> -    if ( !d->arch.vuart.buf )
> -        return -ENOMEM;
> -
> -    return 0;
> -}
> -

Same remark as domain_vgic_init.

Regards,

-- 
Julien Grall

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