Re: [Xen-devel] [PATCH v2 16/27] ARM: vITS: handle CLEAR command

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 03/16/2017 11:20 AM, 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.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> ---
>  xen/arch/arm/vgic-v3-its.c | 35 +++++++++++++++++++++++++++++++++--
>  1 file changed, 33 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/arm/vgic-v3-its.c b/xen/arch/arm/vgic-v3-its.c
> index 267a573..e808f43 100644
> --- a/xen/arch/arm/vgic-v3-its.c
> +++ b/xen/arch/arm/vgic-v3-its.c
> @@ -131,8 +131,8 @@ static void put_devid_evid(struct virt_its *its, struct 
> vits_itte *itte)
>   * protect the ITTs with their less-than-page-size granularity.
>   * Takes and drops the its_lock.
>   */
> -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,
NIT: Please mention in the commit message why you turned those functions 
to static.
> +                      struct vcpu **vcpu, uint32_t *vlpi)
>  {
>      struct vits_itte *itte;
>      int collid;
> @@ -216,6 +216,34 @@ static uint64_t its_cmd_mask_field(uint64_t *its_cmd,
>  #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 *pirq;
> +    struct vcpu *vcpu;
> +    uint32_t vlpi;
> +
> +    if ( !read_itte(its, devid, eventid, &vcpu, &vlpi) )
> +        return -1;
> +
> +    /* 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."

> +    pirq = lpi_to_pending(vcpu, vlpi, false);
> +    if ( pirq )
> +    {
> +        clear_bit(GIC_IRQ_GUEST_QUEUED, &pirq->status);
> +        gic_remove_from_queues(vcpu, vlpi);
> +
> +        /* Mark this pending IRQ struct as availabe again. */
> +        if ( !test_bit(GIC_IRQ_GUEST_VISIBLE, &pirq->status) )
> +            pirq->irq = 0;
> +    }
> +
> +    clear_bit(vlpi - LPI_OFFSET, vcpu->arch.vgic.pendtable);
> +
> +    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,
> @@ -236,6 +264,9 @@ static int vgic_its_handle_cmds(struct domain *d, struct 
> virt_its *its,
>          cmdptr = its->cmdbuf + (its->creadr / sizeof(*its->cmdbuf));
>          switch (its_cmd_get_command(cmdptr))
>          {
> +        case GITS_CMD_CLEAR:
> +            its_handle_clear(its, cmdptr);
Should not you check the return for its_handle_clear?

> +            break;
>          case GITS_CMD_SYNC:
>              /* We handle ITS commands synchronously, so we ignore SYNC. */
>             break;
Regards,

--
Julien Grall

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