Re: [Qemu-devel] [PATCH 1/4] apic: add deliver_msi to APICCommonClass

[Eduardo Habkost]

On Fri, May 06, 2016 at 10:53:45PM +0200, Radim Krčmář wrote:
> The only way to send interrupts from outside of APIC devices is to use
> the MSI-inspired memory mapped interface.  The interface is not
> sufficient because interrupt remapping in extended mode can exceed 8 bit
> destination ids.
> 
> The proper way to deliver interrupts would be to design a bus (QPI), but
> that is a big undertaking.  Real IR unit stores excessive bits in the
> high work of MSI address register, which would be bit [63:40] in memory
> address space, so I was considering two options:
>  - a new special address space for APIC to handle MSI-compatible writes
>  - one callback to the APIC class that delivers extended MSIs
> 
> This patch uses latter option, because it was easier for me, but I think
> the former one could be a tad nicer.
> 
> Signed-off-by: Radim Krčmář <address@hidden>

Reviewed-by: Eduardo Habkost <address@hidden>

But I have a suggestion below:

> ---
>  hw/i386/kvm/apic.c              | 21 ++++++++++++++-------
>  hw/i386/xen/xen_apic.c          |  7 +++++++
>  hw/intc/apic.c                  |  7 +++++++
>  include/hw/i386/apic_internal.h |  5 +++++
>  4 files changed, 33 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/i386/kvm/apic.c b/hw/i386/kvm/apic.c
> index 3c7c8fa00709..7881f13abb96 100644
> --- a/hw/i386/kvm/apic.c
> +++ b/hw/i386/kvm/apic.c
> @@ -147,6 +147,17 @@ static void kvm_apic_external_nmi(APICCommonState *s)
>      run_on_cpu(CPU(s->cpu), do_inject_external_nmi, s);
>  }
>  
> +static void kvm_deliver_msi(MSIMessage *msg)
> +{
> +    int ret;
> +
> +    ret = kvm_irqchip_send_msi(kvm_state, *msg);
> +    if (ret < 0) {
> +        fprintf(stderr, "KVM: injection failed, MSI lost (%s)\n",
> +                strerror(-ret));
> +    }
> +}
> +
>  static uint64_t kvm_apic_mem_read(void *opaque, hwaddr addr,
>                                    unsigned size)
>  {
> @@ -157,13 +168,7 @@ static void kvm_apic_mem_write(void *opaque, hwaddr addr,
>                                 uint64_t data, unsigned size)
>  {
>      MSIMessage msg = { .address = addr, .data = data };
> -    int ret;
> -
> -    ret = kvm_irqchip_send_msi(kvm_state, msg);
> -    if (ret < 0) {
> -        fprintf(stderr, "KVM: injection failed, MSI lost (%s)\n",
> -                strerror(-ret));
> -    }
> +    kvm_deliver_msi(&msg);
>  }

You could call APICCommonClass::deliver_msi() here. Then (in a
follow-up patch?) both kvm_apic_mem_write() and
xen_apic_mem_write() could be replaced by a common function like:

  void apic_msi_write(void *opaque, hwaddr addr, uint64_t data, unsigned size)
  {
      APICommonState *s = opaque;
      APICCommonClass *k = APIC_COMMON_GET_CLASS(s);
      MSIMessage msg = { .address = addr, .data = data };
      k->deliver_msi(&msg);
  }

(apic_mem_writel() is more complex, but maybe it could call the
common function instead of calling apic_send_msi() directly)

>  
>  static const MemoryRegionOps kvm_apic_io_ops = {
> @@ -202,6 +207,8 @@ static void kvm_apic_class_init(ObjectClass *klass, void 
> *data)
>      k->enable_tpr_reporting = kvm_apic_enable_tpr_reporting;
>      k->vapic_base_update = kvm_apic_vapic_base_update;
>      k->external_nmi = kvm_apic_external_nmi;
> +
> +    k->deliver_msi = kvm_deliver_msi;
>  }
>  
>  static const TypeInfo kvm_apic_info = {
> diff --git a/hw/i386/xen/xen_apic.c b/hw/i386/xen/xen_apic.c
> index 21d68ee04b0a..0f34f63d449d 100644
> --- a/hw/i386/xen/xen_apic.c
> +++ b/hw/i386/xen/xen_apic.c
> @@ -68,6 +68,11 @@ static void xen_apic_external_nmi(APICCommonState *s)
>  {
>  }
>  
> +static void xen_deliver_msi(MSIMessage *msi)
> +{
> +    xen_hvm_inject_msi(msi->address, msi->data);
> +}
> +
>  static void xen_apic_class_init(ObjectClass *klass, void *data)
>  {
>      APICCommonClass *k = APIC_COMMON_CLASS(klass);
> @@ -78,6 +83,8 @@ static void xen_apic_class_init(ObjectClass *klass, void 
> *data)
>      k->get_tpr = xen_apic_get_tpr;
>      k->vapic_base_update = xen_apic_vapic_base_update;
>      k->external_nmi = xen_apic_external_nmi;
> +
> +    k->deliver_msi = xen_deliver_msi;
>  }
>  
>  static const TypeInfo xen_apic_info = {
> diff --git a/hw/intc/apic.c b/hw/intc/apic.c
> index 28c2ea540608..b893942c6e73 100644
> --- a/hw/intc/apic.c
> +++ b/hw/intc/apic.c
> @@ -877,6 +877,11 @@ static void apic_realize(DeviceState *dev, Error **errp)
>      msi_nonbroken = true;
>  }
>  
> +static void apic_deliver_msi(MSIMessage *msi)
> +{
> +    apic_send_msi(msi->address, msi->data);
> +}
> +
>  static void apic_class_init(ObjectClass *klass, void *data)
>  {
>      APICCommonClass *k = APIC_COMMON_CLASS(klass);
> @@ -889,6 +894,8 @@ static void apic_class_init(ObjectClass *klass, void 
> *data)
>      k->external_nmi = apic_external_nmi;
>      k->pre_save = apic_pre_save;
>      k->post_load = apic_post_load;
> +
> +    k->deliver_msi = apic_deliver_msi;
>  }
>  
>  static const TypeInfo apic_info = {
> diff --git a/include/hw/i386/apic_internal.h b/include/hw/i386/apic_internal.h
> index 74fe935e8eab..227ef30c5027 100644
> --- a/include/hw/i386/apic_internal.h
> +++ b/include/hw/i386/apic_internal.h
> @@ -146,6 +146,11 @@ typedef struct APICCommonClass
>      void (*pre_save)(APICCommonState *s);
>      void (*post_load)(APICCommonState *s);
>      void (*reset)(APICCommonState *s);
> +
> +    /* deliver_msi emulates an APIC bus and its proper place would be in a 
> new
> +     * device, but it's convenient to have it here for now.
> +     */
> +    void (*deliver_msi)(MSIMessage *msi);
>  } APICCommonClass;
>  
>  struct APICCommonState {
> -- 
> 2.8.2
> 

-- 
Eduardo