Re: [Qemu-devel] [PATCH 5/6] kvm: Don't assume irqchip implies MSI routing via irqfds

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2012-07-25 15:24, Peter Maydell wrote:
> Decouple another x86-specific assumption about what irqchips imply.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  hw/virtio-pci.c   |    4 ++--
>  kvm-all.c         |    3 ++-
>  kvm-stub.c        |    1 +
>  kvm.h             |   12 ++++++++++++
>  target-i386/kvm.c |    4 +++-
>  5 files changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index 4e03f0b..98e02ef 100644
> --- a/hw/virtio-pci.c
> +++ b/hw/virtio-pci.c
> @@ -627,7 +627,7 @@ static int virtio_pci_set_guest_notifiers(void *opaque, bool assign)
>      int r, n;
>  
>      /* Must unset vector notifier while guest notifier is still assigned */
> -    if (kvm_irqchip_in_kernel() && !assign) {
> +    if (kvm_msi_via_irqfd_enabled() && !assign) {
>          msix_unset_vector_notifiers(&proxy->pci_dev);
>          g_free(proxy->vector_irqfd);
>          proxy->vector_irqfd = NULL;
> @@ -645,7 +645,7 @@ static int virtio_pci_set_guest_notifiers(void *opaque, bool assign)
>      }
>  
>      /* Must set vector notifier after guest notifier has been assigned */
> -    if (kvm_irqchip_in_kernel() && assign) {
> +    if (kvm_msi_via_irqfd_enabled() && assign) {
>          proxy->vector_irqfd =
>              g_malloc0(sizeof(*proxy->vector_irqfd) *
>                        msix_nr_vectors_allocated(&proxy->pci_dev));

These are ok.

> diff --git a/kvm-all.c b/kvm-all.c
> index a88b8ad..c624137 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -102,6 +102,7 @@ KVMState *kvm_state;
>  bool kvm_kernel_irqchip;
>  bool kvm_async_interrupt_injection;
>  bool kvm_irqfds_allowed;
> +bool kvm_msi_via_irqfd_allowed;
>  
>  static const KVMCapabilityInfo kvm_required_capabilites[] = {
>      KVM_CAP_INFO(USER_MEMORY),
> @@ -1098,7 +1099,7 @@ int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg)
>      struct kvm_irq_routing_entry kroute;
>      int virq;
>  
> -    if (!kvm_irqchip_in_kernel()) {
> +    if (!kvm_msi_via_irqfd_enabled()) {

This is semantically wrong. Currently, this function is only used for
irqfd. But we will also use it to prepare MSI injections by KVM device
assignment. For other (yet non-existent) in-kernel sources of MSIs we
could use it as well. The proper check is some active version of
has_gsi_routing.

>          return -ENOSYS;
>      }
>  
> diff --git a/kvm-stub.c b/kvm-stub.c
> index 179e5de..6cdeb1c 100644
> --- a/kvm-stub.c
> +++ b/kvm-stub.c
> @@ -21,6 +21,7 @@ KVMState *kvm_state;
>  bool kvm_kernel_irqchip;
>  bool kvm_async_interrupt_injection;
>  bool kvm_irqfds_allowed;
> +bool kvm_msi_via_irqfd_allowed;
>  
>  int kvm_init_vcpu(CPUArchState *env)
>  {
> diff --git a/kvm.h b/kvm.h
> index 2337eb0..1449795 100644
> --- a/kvm.h
> +++ b/kvm.h
> @@ -26,6 +26,7 @@ extern int kvm_allowed;
>  extern bool kvm_kernel_irqchip;
>  extern bool kvm_async_interrupt_injection;
>  extern bool kvm_irqfds_allowed;
> +extern bool kvm_msi_via_irqfd_allowed;
>  
>  #if defined CONFIG_KVM || !defined NEED_CPU_H
>  #define kvm_enabled()           (kvm_allowed)
> @@ -47,11 +48,22 @@ extern bool kvm_irqfds_allowed;
>   * with a configuration where it is meaningful to use them).
>   */
>  #define kvm_irqfds_enabled() (kvm_irqfds_allowed)
> +/**
> + * kvm_msi_via_irqfd_enabled:
> + *
> + * Returns: true if we can route a PCI MSI (Message Signaled Interrupt)
> + * to a KVM CPU via an irqfd. This requires that the kernel supports
> + * this and that we're running in a configuration that permits it.
> + * This should be checked before calling MSI related functions such as
> + * kvm_irqchip_add_msi_route.

See above.

> + */
> +#define kvm_msi_via_irqfd_enabled() (kvm_msi_via_irqfd_allowed)
>  #else
>  #define kvm_enabled()           (0)
>  #define kvm_irqchip_in_kernel() (false)
>  #define kvm_async_interrupt_injection() (false)
>  #define kvm_irqfds_enabled() (false)
> +#define kvm_msi_via_irqfd_enabled() (false)
>  #endif
>  
>  struct kvm_run;
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 8e19a4d..03db818 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -2046,7 +2046,9 @@ void kvm_arch_init_irq_routing(KVMState *s)
>          no_hpet = 1;
>      }
>      /* We know at this point that we're using the in-kernel
> -     * irqchip, so we can use irqfds.
> +     * irqchip, so we can use irqfds, and on x86 we know
> +     * we can use msi via irqfd.
>       */
>      kvm_irqfds_allowed = true;
> +    kvm_msi_via_irqfd_allowed = true;
>  }
> 

Jan

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