Re: [PATCH V4 18/24] xen/dm: Introduce xendevicemodel_set_irq_level DM op

[Stefano Stabellini <sstabellini@kernel.org>]

On Tue, 12 Jan 2021, Oleksandr Tyshchenko wrote:
> From: Julien Grall <julien.grall@arm.com>
> 
> This patch adds ability to the device emulator to notify otherend
> (some entity running in the guest) using a SPI and implements Arm
> specific bits for it. Proposed interface allows emulator to set
> the logical level of a one of a domain's IRQ lines.
> 
> We can't reuse the existing DM op (xen_dm_op_set_isa_irq_level)
> to inject an interrupt as the "isa_irq" field is only 8-bit and
> able to cover IRQ 0 - 255, whereas we need a wider range (0 - 1020).
> 
> Please note, for egde-triggered interrupt (which is used for
> the virtio-mmio emulation) we only trigger the interrupt on Arm
> if the level is asserted (rising edge) and do nothing if the level
> is deasserted (falling edge), so the call could be named "trigger_irq"
> (without the level parameter). But, in order to model the line closely
> (to be able to support level-triggered interrupt) we need to know whether
> the line is low or high, so the proposed interface has been chosen.
> However, it is worth mentioning that in case of the level-triggered
> interrupt, we should keep injecting the interrupt to the guest until
> the line is deasserted (this is not covered by current patch).
> 
> Signed-off-by: Julien Grall <julien.grall@arm.com>
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> [On Arm only]
> Tested-by: Wei Chen <Wei.Chen@arm.com>

Acked-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
> Please note, this is a split/cleanup/hardening of Julien's PoC:
> "Add support for Guest IO forwarding to a device emulator"
> 
> Changes RFC -> V1:
>    - check incoming parameters in arch_dm_op()
>    - add explicit padding to struct xen_dm_op_set_irq_level
> 
> Changes V1 -> V2:
>    - update the author of a patch
>    - update patch description
>    - check that padding is always 0
>    - mention that interface is Arm only and only SPIs are
>      supported for now
>    - allow to set the logical level of a line for non-allocated
>      interrupts only
>    - add xen_dm_op_set_irq_level_t
> 
> Changes V2 -> V3:
>    - no changes
> 
> Changes V3 -> V4:
>    - update patch description
>    - update patch according to the IOREQ related dm-op handling changes
> ---
>  tools/include/xendevicemodel.h               |  4 +++
>  tools/libs/devicemodel/core.c                | 18 ++++++++++
>  tools/libs/devicemodel/libxendevicemodel.map |  1 +
>  xen/arch/arm/dm.c                            | 54 +++++++++++++++++++++++++++-
>  xen/include/public/hvm/dm_op.h               | 16 +++++++++
>  5 files changed, 92 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/include/xendevicemodel.h b/tools/include/xendevicemodel.h
> index e877f5c..c06b3c8 100644
> --- a/tools/include/xendevicemodel.h
> +++ b/tools/include/xendevicemodel.h
> @@ -209,6 +209,10 @@ int xendevicemodel_set_isa_irq_level(
>      xendevicemodel_handle *dmod, domid_t domid, uint8_t irq,
>      unsigned int level);
>  
> +int xendevicemodel_set_irq_level(
> +    xendevicemodel_handle *dmod, domid_t domid, unsigned int irq,
> +    unsigned int level);
> +
>  /**
>   * This function maps a PCI INTx line to a an IRQ line.
>   *
> diff --git a/tools/libs/devicemodel/core.c b/tools/libs/devicemodel/core.c
> index 4d40639..30bd79f 100644
> --- a/tools/libs/devicemodel/core.c
> +++ b/tools/libs/devicemodel/core.c
> @@ -430,6 +430,24 @@ int xendevicemodel_set_isa_irq_level(
>      return xendevicemodel_op(dmod, domid, 1, &op, sizeof(op));
>  }
>  
> +int xendevicemodel_set_irq_level(
> +    xendevicemodel_handle *dmod, domid_t domid, uint32_t irq,
> +    unsigned int level)
> +{
> +    struct xen_dm_op op;
> +    struct xen_dm_op_set_irq_level *data;
> +
> +    memset(&op, 0, sizeof(op));
> +
> +    op.op = XEN_DMOP_set_irq_level;
> +    data = &op.u.set_irq_level;
> +
> +    data->irq = irq;
> +    data->level = level;
> +
> +    return xendevicemodel_op(dmod, domid, 1, &op, sizeof(op));
> +}
> +
>  int xendevicemodel_set_pci_link_route(
>      xendevicemodel_handle *dmod, domid_t domid, uint8_t link, uint8_t irq)
>  {
> diff --git a/tools/libs/devicemodel/libxendevicemodel.map b/tools/libs/devicemodel/libxendevicemodel.map
> index 561c62d..a0c3012 100644
> --- a/tools/libs/devicemodel/libxendevicemodel.map
> +++ b/tools/libs/devicemodel/libxendevicemodel.map
> @@ -32,6 +32,7 @@ VERS_1.2 {
>  	global:
>  		xendevicemodel_relocate_memory;
>  		xendevicemodel_pin_memory_cacheattr;
> +		xendevicemodel_set_irq_level;
>  } VERS_1.1;
>  
>  VERS_1.3 {
> diff --git a/xen/arch/arm/dm.c b/xen/arch/arm/dm.c
> index e6dedf4..804830a 100644
> --- a/xen/arch/arm/dm.c
> +++ b/xen/arch/arm/dm.c
> @@ -20,6 +20,8 @@
>  #include <xen/ioreq.h>
>  #include <xen/nospec.h>
>  
> +#include <asm/vgic.h>
> +
>  static int dm_op(const struct dmop_args *op_args)
>  {
>      struct domain *d;
> @@ -35,6 +37,7 @@ static int dm_op(const struct dmop_args *op_args)
>          [XEN_DMOP_unmap_io_range_from_ioreq_server] = sizeof(struct xen_dm_op_ioreq_server_range),
>          [XEN_DMOP_set_ioreq_server_state]           = sizeof(struct xen_dm_op_set_ioreq_server_state),
>          [XEN_DMOP_destroy_ioreq_server]             = sizeof(struct xen_dm_op_destroy_ioreq_server),
> +        [XEN_DMOP_set_irq_level]                    = sizeof(struct xen_dm_op_set_irq_level),
>      };
>  
>      rc = rcu_lock_remote_domain_by_id(op_args->domid, &d);
> @@ -73,7 +76,56 @@ static int dm_op(const struct dmop_args *op_args)
>      if ( op.pad )
>          goto out;
>  
> -    rc = ioreq_server_dm_op(&op, d, &const_op);
> +    switch ( op.op )
> +    {
> +    case XEN_DMOP_set_irq_level:
> +    {
> +        const struct xen_dm_op_set_irq_level *data =
> +            &op.u.set_irq_level;
> +        unsigned int i;
> +
> +        /* Only SPIs are supported */
> +        if ( (data->irq < NR_LOCAL_IRQS) || (data->irq >= vgic_num_irqs(d)) )
> +        {
> +            rc = -EINVAL;
> +            break;
> +        }
> +
> +        if ( data->level != 0 && data->level != 1 )
> +        {
> +            rc = -EINVAL;
> +            break;
> +        }
> +
> +        /* Check that padding is always 0 */
> +        for ( i = 0; i < sizeof(data->pad); i++ )
> +        {
> +            if ( data->pad[i] )
> +            {
> +                rc = -EINVAL;
> +                break;
> +            }
> +        }
> +
> +        /*
> +         * Allow to set the logical level of a line for non-allocated
> +         * interrupts only.
> +         */
> +        if ( test_bit(data->irq, d->arch.vgic.allocated_irqs) )
> +        {
> +            rc = -EINVAL;
> +            break;
> +        }
> +
> +        vgic_inject_irq(d, NULL, data->irq, data->level);
> +        rc = 0;
> +        break;
> +    }
> +
> +    default:
> +        rc = ioreq_server_dm_op(&op, d, &const_op);
> +        break;
> +    }
>  
>      if ( (!rc || rc == -ERESTART) &&
>           !const_op && copy_to_guest_offset(op_args->buf[0].h, offset,
> diff --git a/xen/include/public/hvm/dm_op.h b/xen/include/public/hvm/dm_op.h
> index 66cae1a..1f70d58 100644
> --- a/xen/include/public/hvm/dm_op.h
> +++ b/xen/include/public/hvm/dm_op.h
> @@ -434,6 +434,21 @@ struct xen_dm_op_pin_memory_cacheattr {
>  };
>  typedef struct xen_dm_op_pin_memory_cacheattr xen_dm_op_pin_memory_cacheattr_t;
>  
> +/*
> + * XEN_DMOP_set_irq_level: Set the logical level of a one of a domain's
> + *                         IRQ lines (currently Arm only).
> + * Only SPIs are supported.
> + */
> +#define XEN_DMOP_set_irq_level 19
> +
> +struct xen_dm_op_set_irq_level {
> +    uint32_t irq;
> +    /* IN - Level: 0 -> deasserted, 1 -> asserted */
> +    uint8_t level;
> +    uint8_t pad[3];
> +};
> +typedef struct xen_dm_op_set_irq_level xen_dm_op_set_irq_level_t;
> +
>  struct xen_dm_op {
>      uint32_t op;
>      uint32_t pad;
> @@ -447,6 +462,7 @@ struct xen_dm_op {
>          xen_dm_op_track_dirty_vram_t track_dirty_vram;
>          xen_dm_op_set_pci_intx_level_t set_pci_intx_level;
>          xen_dm_op_set_isa_irq_level_t set_isa_irq_level;
> +        xen_dm_op_set_irq_level_t set_irq_level;
>          xen_dm_op_set_pci_link_route_t set_pci_link_route;
>          xen_dm_op_modified_memory_t modified_memory;
>          xen_dm_op_set_mem_type_t set_mem_type;
> -- 
> 2.7.4
>