Re: [PATCH v1 2/4] hw/xen: xenpvh: Disable buffered IOREQs for ARM

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 16 Sep 2024, Edgar E. Iglesias wrote:
> From: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxx>
> 
> Add a way to enable/disable buffered IOREQs for PVH machines
> and disable them for ARM. ARM does not support buffered
> IOREQ's nor the legacy way to map IOREQ info pages.
> 
> See the following for more details:
> https://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=2fbd7e609e1803ac5e5c26e22aa8e4b5a6cddbb1
> https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/arch/arm/ioreq.c;h=2e829d2e7f3760401b96fa7c930e2015fb1cf463;hb=HEAD#l138
> 
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xxxxxxx>
> ---
>  hw/arm/xen-pvh.c                | 3 +++
>  hw/i386/xen/xen-pvh.c           | 3 +++
>  hw/xen/xen-pvh-common.c         | 2 +-
>  include/hw/xen/xen-pvh-common.h | 3 +++
>  4 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/arm/xen-pvh.c b/hw/arm/xen-pvh.c
> index 04cb9855af..28af3910ea 100644
> --- a/hw/arm/xen-pvh.c
> +++ b/hw/arm/xen-pvh.c
> @@ -66,6 +66,9 @@ static void xen_arm_machine_class_init(ObjectClass *oc, 
> void *data)
>       */
>      mc->max_cpus = GUEST_MAX_VCPUS;
>  
> +    /* Xen/ARM does not use buffered IOREQs.  */
> +    xpc->handle_bufioreq = HVM_IOREQSRV_BUFIOREQ_OFF;
> +
>      /* List of supported features known to work on PVH ARM.  */
>      xpc->has_tpm = true;
>      xpc->has_virtio_mmio = true;
> diff --git a/hw/i386/xen/xen-pvh.c b/hw/i386/xen/xen-pvh.c
> index 45645667e9..f1f02d3311 100644
> --- a/hw/i386/xen/xen-pvh.c
> +++ b/hw/i386/xen/xen-pvh.c
> @@ -89,6 +89,9 @@ static void xen_pvh_machine_class_init(ObjectClass *oc, 
> void *data)
>      /* We have an implementation specific init to create CPU objects.  */
>      xpc->init = xen_pvh_init;
>  
> +    /* Enable buffered IOREQs.  */
> +    xpc->handle_bufioreq = HVM_IOREQSRV_BUFIOREQ_ATOMIC;
> +
>      /*
>       * PCI INTX routing.
>       *
> diff --git a/hw/xen/xen-pvh-common.c b/hw/xen/xen-pvh-common.c
> index 08641fdcec..76a9b2b945 100644
> --- a/hw/xen/xen-pvh-common.c
> +++ b/hw/xen/xen-pvh-common.c
> @@ -195,7 +195,7 @@ static void xen_pvh_init(MachineState *ms)
>  
>      xen_pvh_init_ram(s, sysmem);
>      xen_register_ioreq(&s->ioreq, ms->smp.max_cpus,
> -                       HVM_IOREQSRV_BUFIOREQ_ATOMIC,
> +                       xpc->handle_bufioreq,
>                         &xen_memory_listener);
>  
>      if (s->cfg.virtio_mmio_num) {
> diff --git a/include/hw/xen/xen-pvh-common.h b/include/hw/xen/xen-pvh-common.h
> index bc09eea936..62c44a1ce7 100644
> --- a/include/hw/xen/xen-pvh-common.h
> +++ b/include/hw/xen/xen-pvh-common.h
> @@ -43,6 +43,9 @@ struct XenPVHMachineClass {
>       */
>      int (*set_pci_link_route)(uint8_t line, uint8_t irq);
>  
> +    /* Allow implementations to optionally enable buffered ioreqs.  */
> +    int handle_bufioreq;

Looking at the corresponding Xen interface this field is uint8_t. I
think it would be better to use the same type here and also as a
parameter to xen_register_ioreq in QEMU



>      /*
>       * Each implementation can optionally enable features that it
>       * supports and are known to work.
> -- 
> 2.43.0
>