Re: [PATCH v4] KVM: Introduce direct MSI message injection for in-kernel irqchips

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Mar 30, 2012 at 09:45:35AM +0200, Jan Kiszka wrote:
> On 2012-03-29 21:41, Michael S. Tsirkin wrote:
> > On Thu, Mar 29, 2012 at 09:14:12PM +0200, Jan Kiszka wrote:
> >> Currently, MSI messages can only be injected to in-kernel irqchips by
> >> defining a corresponding IRQ route for each message. This is not only
> >> unhandy if the MSI messages are generated "on the fly" by user space,
> >> IRQ routes are a limited resource that user space has to manage
> >> carefully.
> >>
> >> By providing a direct injection path, we can both avoid using up limited
> >> resources and simplify the necessary steps for user land.
> >>
> >> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> >> ---
> >>
> >> Changes in v4:
> >>  - Fix the build by factoring out kvm_send_userspace_msi:
> >>    irqchip_in_kernel is not generically available. But abstracting it
> >>    for all arch is tricky and therefore left to the poor people who have
> >>    to introduce non-x86 irqchip support to this x86-focused corner.
> >>
> >> Lesson (probably not) learned: Never underestimate the complexity of
> >> trivial changes.
> >>
> >>  Documentation/virtual/kvm/api.txt |   21 +++++++++++++++++++++
> >>  arch/x86/kvm/Kconfig              |    1 +
> >>  include/linux/kvm.h               |   11 +++++++++++
> >>  include/linux/kvm_host.h          |    2 ++
> >>  virt/kvm/Kconfig                  |    3 +++
> >>  virt/kvm/irq_comm.c               |   14 ++++++++++++++
> >>  virt/kvm/kvm_main.c               |   14 ++++++++++++++
> >>  7 files changed, 66 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> >> index 81ff39f..ed27d1b 100644
> >> --- a/Documentation/virtual/kvm/api.txt
> >> +++ b/Documentation/virtual/kvm/api.txt
> >> @@ -1482,6 +1482,27 @@ See KVM_ASSIGN_DEV_IRQ for the data structure.  The target device is specified
> >>  by assigned_dev_id.  In the flags field, only KVM_DEV_ASSIGN_MASK_INTX is
> >>  evaluated.
> >>  
> >> +4.61 KVM_SIGNAL_MSI
> >> +
> >> +Capability: KVM_CAP_SIGNAL_MSI
> >> +Architectures: x86
> >> +Type: vm ioctl
> >> +Parameters: struct kvm_msi (in)
> >> +Returns: >0 on delivery, 0 if guest blocked the MSI, and -1 on error
> >> +
> >> +Directly inject a MSI message. Only valid with in-kernel irqchip that handles
> >> +MSI messages.
> >> +
> >> +struct kvm_msi {
> >> +	__u32 address_lo;
> >> +	__u32 address_hi;
> >> +	__u32 data;
> >> +	__u32 flags;
> >> +	__u8  pad[16];
> >> +};
> >> +
> >> +No flags are defined so far. The corresponding field must be 0.
> >> +
> >>  4.62 KVM_CREATE_SPAPR_TCE
> >>  
> >>  Capability: KVM_CAP_SPAPR_TCE
> >> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> >> index 1a7fe86..a28f338 100644
> >> --- a/arch/x86/kvm/Kconfig
> >> +++ b/arch/x86/kvm/Kconfig
> >> @@ -36,6 +36,7 @@ config KVM
> >>  	select TASKSTATS
> >>  	select TASK_DELAY_ACCT
> >>  	select PERF_EVENTS
> >> +	select HAVE_KVM_MSI
> >>  	---help---
> >>  	  Support hosting fully virtualized guest machines using hardware
> >>  	  virtualization extensions.  You will need a fairly recent
> >> diff --git a/include/linux/kvm.h b/include/linux/kvm.h
> >> index 7a9dd4b..225b452 100644
> >> --- a/include/linux/kvm.h
> >> +++ b/include/linux/kvm.h
> >> @@ -590,6 +590,7 @@ struct kvm_ppc_pvinfo {
> >>  #define KVM_CAP_SYNC_REGS 74
> >>  #define KVM_CAP_PCI_2_3 75
> >>  #define KVM_CAP_KVMCLOCK_CTRL 76
> >> +#define KVM_CAP_SIGNAL_MSI 77
> >>  
> >>  #ifdef KVM_CAP_IRQ_ROUTING
> >>  
> >> @@ -715,6 +716,14 @@ struct kvm_one_reg {
> >>  	__u64 addr;
> >>  };
> >>  
> >> +struct kvm_msi {
> >> +	__u32 address_lo;
> >> +	__u32 address_hi;
> >> +	__u32 data;
> >> +	__u32 flags;
> >> +	__u8  pad[16];
> >> +};
> >> +
> >>  /*
> >>   * ioctls for VM fds
> >>   */
> >> @@ -789,6 +798,8 @@ struct kvm_s390_ucas_mapping {
> >>  /* Available with KVM_CAP_PCI_2_3 */
> >>  #define KVM_ASSIGN_SET_INTX_MASK  _IOW(KVMIO,  0xa4, \
> >>  				       struct kvm_assigned_pci_dev)
> >> +/* Available with KVM_CAP_SIGNAL_MSI */
> >> +#define KVM_SIGNAL_MSI            _IOW(KVMIO,  0xa5, struct kvm_msi)
> >>  
> >>  /*
> >>   * ioctls for vcpu fds
> >> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> >> index 6cf158c..35c69d6 100644
> >> --- a/include/linux/kvm_host.h
> >> +++ b/include/linux/kvm_host.h
> >> @@ -774,6 +774,8 @@ int kvm_set_irq_routing(struct kvm *kvm,
> >>  			unsigned flags);
> >>  void kvm_free_irq_routing(struct kvm *kvm);
> >>  
> >> +int kvm_send_userspace_msi(struct kvm *kvm, struct kvm_msi *msi);
> >> +
> >>  #else
> >>  
> >>  static inline void kvm_free_irq_routing(struct kvm *kvm) {}
> >> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> >> index f63ccb0..28694f4 100644
> >> --- a/virt/kvm/Kconfig
> >> +++ b/virt/kvm/Kconfig
> >> @@ -18,3 +18,6 @@ config KVM_MMIO
> >>  
> >>  config KVM_ASYNC_PF
> >>         bool
> >> +
> >> +config HAVE_KVM_MSI
> >> +       bool
> >> diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
> >> index 9f614b4..a6a0365 100644
> >> --- a/virt/kvm/irq_comm.c
> >> +++ b/virt/kvm/irq_comm.c
> >> @@ -138,6 +138,20 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
> >>  	return kvm_irq_delivery_to_apic(kvm, NULL, &irq);
> >>  }
> >>  
> >> +int kvm_send_userspace_msi(struct kvm *kvm, struct kvm_msi *msi)
> >> +{
> >> +	struct kvm_kernel_irq_routing_entry route;
> >> +
> >> +	if (!irqchip_in_kernel(kvm) || msi->flags != 0)
> >> +		return -EINVAL;
> >> +
> >> +	route.msi.address_lo = msi->address_lo;
> >> +	route.msi.address_hi = msi->address_hi;
> >> +	route.msi.data = msi->data;
> >> +
> >> +	return kvm_set_msi(&route, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1);
> >> +}
> >> +
> >>  /*
> >>   * Return value:
> >>   *  < 0   Interrupt was ignored (masked or not delivered for other reasons)
> >> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> >> index a612bc8..5addfa8 100644
> >> --- a/virt/kvm/kvm_main.c
> >> +++ b/virt/kvm/kvm_main.c
> >> @@ -2063,6 +2063,17 @@ static long kvm_vm_ioctl(struct file *filp,
> >>  		mutex_unlock(&kvm->lock);
> >>  		break;
> >>  #endif
> >> +#ifdef CONFIG_HAVE_KVM_MSI
> >> +	case KVM_SIGNAL_MSI: {
> >> +		struct kvm_msi msi;
> >> +
> >> +		r = -EFAULT;
> >> +		if (copy_from_user(&msi, argp, sizeof msi))
> >> +			goto out;
> > 
> > Wait a second, we should validate flags: you say
> > "this field should be 0" so we should check it.
> 
> Yep, see kvm_send_userspace_msi.
> 
> Jan

Right, missed this. Thanks.

> > 
> >> +		r = kvm_send_userspace_msi(kvm, &msi);
> >> +		break;
> >> +	}
> >> +#endif
> >>  	default:
> >>  		r = kvm_arch_vm_ioctl(filp, ioctl, arg);
> >>  		if (r == -ENOTTY)
> >> @@ -2191,6 +2202,9 @@ static long kvm_dev_ioctl_check_extension_generic(long arg)
> >>  	case KVM_CAP_SET_BOOT_CPU_ID:
> >>  #endif
> >>  	case KVM_CAP_INTERNAL_ERROR_DATA:
> >> +#ifdef CONFIG_HAVE_KVM_MSI
> >> +	case KVM_CAP_SIGNAL_MSI:
> >> +#endif
> >>  		return 1;
> >>  #ifdef CONFIG_HAVE_KVM_IRQCHIP
> >>  	case KVM_CAP_IRQ_ROUTING:
> >> -- 
> >> 1.7.3.4
> 
> -- 
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