Re: [PATCH v4 16/27] ARM: vITS: handle CLEAR command

[Julien Grall <julien.grall@arm.com>]

Hi Andre,

On 03/04/17 21:28, Andre Przywara wrote:
> This introduces the ITS command handler for the CLEAR command, which
> clears the pending state of an LPI.
> This removes a not-yet injected, but already queued IRQ from a VCPU.
> As read_itte() is now eventually used, we add the static keyword.
>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
>  xen/arch/arm/vgic-v3-its.c | 31 +++++++++++++++++++++++++++++--
>  1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/arm/vgic-v3-its.c b/xen/arch/arm/vgic-v3-its.c
> index fcfea3b..cc1d7a0 100644
> --- a/xen/arch/arm/vgic-v3-its.c
> +++ b/xen/arch/arm/vgic-v3-its.c
> @@ -186,8 +186,8 @@ static void put_itte(struct virt_its *its, struct vits_itte *itte)
>   * This function takes care of the locking by taking the its_lock itself, so
>   * a caller shall not hold this. Upon returning, the lock is dropped again.
>   */
> -bool read_itte(struct virt_its *its, uint32_t devid, uint32_t evid,
> -               struct vcpu **vcpu, uint32_t *vlpi)
> +static bool read_itte(struct virt_its *its, uint32_t devid, uint32_t evid,
> +                      struct vcpu **vcpu, uint32_t *vlpi)
>  {
>      struct vits_itte *itte;
>      uint16_t collid;
> @@ -273,6 +273,30 @@ static uint64_t its_cmd_mask_field(uint64_t *its_cmd, unsigned int word,
>  #define its_cmd_get_target_addr(cmd)    its_cmd_mask_field(cmd, 2, 16, 32)
>  #define its_cmd_get_validbit(cmd)       its_cmd_mask_field(cmd, 2, 63,  1)
>
> +static int its_handle_clear(struct virt_its *its, uint64_t *cmdptr)
> +{
> +    uint32_t devid = its_cmd_get_deviceid(cmdptr);
> +    uint32_t eventid = its_cmd_get_id(cmdptr);
> +    struct pending_irq *p;
> +    struct vcpu *vcpu;
> +    uint32_t vlpi;
> +
> +    if ( !read_itte(its, devid, eventid, &vcpu, &vlpi) )
> +        return -1;
> +
> +    p = lpi_to_pending(its->d, vlpi);
> +    if ( !p )
> +        return -1;
> +
> +    clear_bit(GIC_IRQ_GUEST_LPI_PENDING, &p->status);
> +
> +    /* Remove a pending, but not yet injected guest IRQ. */

Copying Stefano's comment from last year:

"We need to check that the vlpi hasn't already been added to an LR
register. We can do that with GIC_IRQ_GUEST_VISIBLE.

In case GIC_IRQ_GUEST_VISIBLE is set, we need to clear the lr
(clear_lr). If we don't handle this case, we should at least print a
warning."

I will let Stefano comments more here.

> +    clear_bit(GIC_IRQ_GUEST_QUEUED, &p->status);
> +    gic_remove_from_queues(vcpu, vlpi);
> +
> +    return 0;
> +}
> +
>  #define ITS_CMD_BUFFER_SIZE(baser)      ((((baser) & 0xff) + 1) << 12)
>
>  static int vgic_its_handle_cmds(struct domain *d, struct virt_its *its,
> @@ -310,6 +334,9 @@ static int vgic_its_handle_cmds(struct domain *d, struct virt_its *its,
>
>          switch ( its_cmd_get_command(cmdptr) )
>          {
> +        case GITS_CMD_CLEAR:
> +            ret = its_handle_clear(its, cmdptr);
> +            break;
>          case GITS_CMD_SYNC:
>              /* We handle ITS commands synchronously, so we ignore SYNC. */
>  	    break;
>

Regards,

-- 
Julien Grall

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