Re: [PATCH v8 5/5] KVM: arm/arm64: add irqfd support

Eric Auger
2015-03-02T16:11:37Z

On 02/23/2015 10:45 PM, Christoffer Dall wrote:
> On Mon, Jan 19, 2015 at 05:43:13PM +0100, Eric Auger wrote:
>> This patch enables irqfd on arm/arm64.
>>
>> Both irqfd and resamplefd are supported. Injection is implemented
>> in vgic.c without routing.
>>
>> This patch enables CONFIG_HAVE_KVM_EVENTFD and CONFIG_HAVE_KVM_IRQFD.
>>
>> KVM_CAP_IRQFD is now advertised. KVM_CAP_IRQFD_RESAMPLE capability
>> automatically is advertised as soon as CONFIG_HAVE_KVM_IRQFD is set.
>>
>> Irqfd injection is restricted to SPI. The rationale behind not
>> supporting PPI irqfd injection is that any device using a PPI would
>> be a private-to-the-CPU device (timer for instance), so its state
>> would have to be context-switched along with the VCPU and would
>> require in-kernel wiring anyhow. It is not a relevant use case for
>> irqfds.
>>
>> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>>
>> ---
>> v7 -> v8:
>> - remove kvm_irq_has_notifier call
>> - part of dist locking changes now are part of previous patch file
>> - remove gic_initialized() check in kvm_set_irq
>> - remove Christoffer's Reviewed-by after this change
>>
>> v5 -> v6:
>> - KVM_CAP_IRQFD support depends on vgic_present
>> - add Christoffer's Reviewed-by
>>
>> v4 -> v5:
>> - squash [PATCH v4 3/3] KVM: arm64: add irqfd support into this patch
>> - some rewording in Documentation/virtual/kvm/api.txt and in vgic
>> vgic_process_maintenance unlock comment.
>> - move explanation of why not supporting PPI into commit message
>> - in case of injection before gic readiness, -ENODEV is returned. It is
>> up to the user space to avoid this situation.
>>
>> v3 -> v4:
>> - reword commit message
>> - explain why we unlock the distributor before calling kvm_notify_acked_irq
>> - rename is_assigned_irq into has_notifier
>> - change EOI and injection kvm_debug format string
>> - remove error local variable in kvm_set_irq
>> - Move HAVE_KVM_IRQCHIP unset in a separate patch
>> - handle case were the irqfd injection is attempted before the vgic is ready.
>> in such a case the notifier, if any, is called immediatly
>> - use nr_irqs to test spi is within correct range
>>
>> v2 -> v3:
>> - removal of irq.h from eventfd.c put in a separate patch to increase
>> visibility
>> - properly expose KVM_CAP_IRQFD capability in arm.c
>> - remove CONFIG_HAVE_KVM_IRQCHIP meaningfull only if irq_comm.c is used
>>
>> v1 -> v2:
>> - rebase on 3.17rc1
>> - move of the dist unlock in process_maintenance
>> - remove of dist lock in __kvm_vgic_sync_hwstate
>> - rewording of the commit message (add resamplefd reference)
>> - remove irq.h
>> ---
>> Documentation/virtual/kvm/api.txt | 6 +++++-
>> arch/arm/include/uapi/asm/kvm.h | 3 +++
>> arch/arm/kvm/Kconfig | 2 ++
>> arch/arm/kvm/Makefile | 2 +-
>> arch/arm/kvm/arm.c | 5 +++++
>> arch/arm64/include/uapi/asm/kvm.h | 3 +++
>> arch/arm64/kvm/Kconfig | 2 ++
>> arch/arm64/kvm/Makefile | 2 +-
>> virt/kvm/arm/vgic.c | 45 +++++++++++++++++++++++++++++++++++++++
>> 9 files changed, 67 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
>> index 0007fef..5ed8088 100644
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -2231,7 +2231,7 @@ into the hash PTE second double word).
>> 4.75 KVM_IRQFD
>>
>> Capability: KVM_CAP_IRQFD
>> -Architectures: x86 s390
>> +Architectures: x86 s390 arm arm64
>> Type: vm ioctl
>> Parameters: struct kvm_irqfd (in)
>> Returns: 0 on success, -1 on error
>> @@ -2257,6 +2257,10 @@ Note that closing the resamplefd is not sufficient to disable the
>> irqfd. The KVM_IRQFD_FLAG_RESAMPLE is only necessary on assignment
>> and need not be specified with KVM_IRQFD_FLAG_DEASSIGN.
>>
>> +On ARM/ARM64, the gsi field in the kvm_irqfd struct specifies the Shared
>> +Peripheral Interrupt (SPI) index, such that the GIC interrupt ID is
>> +given by gsi + 32.
>> +
>> 4.76 KVM_PPC_ALLOCATE_HTAB
>>
>> Capability: KVM_CAP_PPC_ALLOC_HTAB
>> diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
>> index 0db25bc..2499867 100644
>> --- a/arch/arm/include/uapi/asm/kvm.h
>> +++ b/arch/arm/include/uapi/asm/kvm.h
>> @@ -198,6 +198,9 @@ struct kvm_arch_memory_slot {
>> /* Highest supported SPI, from VGIC_NR_IRQS */
>> #define KVM_ARM_IRQ_GIC_MAX 127
>>
>> +/* One single KVM irqchip, ie. the VGIC */
>> +#define KVM_NR_IRQCHIPS 1
>> +
>> /* PSCI interface */
>> #define KVM_PSCI_FN_BASE 0x95c1ba5e
>> #define KVM_PSCI_FN(n) (KVM_PSCI_FN_BASE + (n))
>> diff --git a/arch/arm/kvm/Kconfig b/arch/arm/kvm/Kconfig
>> index 9f581b1..e519a40 100644
>> --- a/arch/arm/kvm/Kconfig
>> +++ b/arch/arm/kvm/Kconfig
>> @@ -24,6 +24,7 @@ config KVM
>> select KVM_MMIO
>> select KVM_ARM_HOST
>> depends on ARM_VIRT_EXT && ARM_LPAE
>> + select HAVE_KVM_EVENTFD
>> ---help---
>> Support hosting virtualized guest machines. You will also
>> need to select one or more of the processor modules below.
>> @@ -55,6 +56,7 @@ config KVM_ARM_MAX_VCPUS
>> config KVM_ARM_VGIC
>> bool "KVM support for Virtual GIC"
>> depends on KVM_ARM_HOST && OF
>> + select HAVE_KVM_IRQFD
>> default y
>> ---help---
>> Adds support for a hardware assisted, in-kernel GIC emulation.
>> diff --git a/arch/arm/kvm/Makefile b/arch/arm/kvm/Makefile
>> index f7057ed..859db09 100644
>> --- a/arch/arm/kvm/Makefile
>> +++ b/arch/arm/kvm/Makefile
>> @@ -15,7 +15,7 @@ AFLAGS_init.o := -Wa,-march=armv7-a$(plus_virt)
>> AFLAGS_interrupts.o := -Wa,-march=armv7-a$(plus_virt)
>>
>> KVM := ../../../virt/kvm
>> -kvm-arm-y = $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o
>> +kvm-arm-y = $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/eventfd.o
>>
>> obj-y += kvm-arm.o init.o interrupts.o
>> obj-y += arm.o handle_exit.o guest.o mmu.o emulate.o reset.o
>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>> index 9c905b4..8f8c1da 100644
>> --- a/arch/arm/kvm/arm.c
>> +++ b/arch/arm/kvm/arm.c
>> @@ -172,6 +172,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>> case KVM_CAP_IRQCHIP:
>> r = vgic_present;
>> break;
>> +#ifdef CONFIG_HAVE_KVM_IRQFD
>> + case KVM_CAP_IRQFD:
>> + r = vgic_present;
>> + break;
>> +#endif
>> case KVM_CAP_DEVICE_CTRL:
>> case KVM_CAP_USER_MEMORY:
>> case KVM_CAP_SYNC_MMU:
>> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
>> index 480af34..b35c95a 100644
>> --- a/arch/arm64/include/uapi/asm/kvm.h
>> +++ b/arch/arm64/include/uapi/asm/kvm.h
>> @@ -184,6 +184,9 @@ struct kvm_arch_memory_slot {
>> /* Highest supported SPI, from VGIC_NR_IRQS */
>> #define KVM_ARM_IRQ_GIC_MAX 127
>>
>> +/* One single KVM irqchip, ie. the VGIC */
>> +#define KVM_NR_IRQCHIPS 1
>> +
>> /* PSCI interface */
>> #define KVM_PSCI_FN_BASE 0x95c1ba5e
>> #define KVM_PSCI_FN(n) (KVM_PSCI_FN_BASE + (n))
>> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
>> index 279e1a0..09c25c2 100644
>> --- a/arch/arm64/kvm/Kconfig
>> +++ b/arch/arm64/kvm/Kconfig
>> @@ -26,6 +26,7 @@ config KVM
>> select KVM_ARM_HOST
>> select KVM_ARM_VGIC
>> select KVM_ARM_TIMER
>> + select HAVE_KVM_EVENTFD
>> ---help---
>> Support hosting virtualized guest machines.
>>
>> @@ -50,6 +51,7 @@ config KVM_ARM_MAX_VCPUS
>> config KVM_ARM_VGIC
>> bool
>> depends on KVM_ARM_HOST && OF
>> + select HAVE_KVM_IRQFD
>> ---help---
>> Adds support for a hardware assisted, in-kernel GIC emulation.
>>
>> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
>> index 32a0961..2e6b827 100644
>> --- a/arch/arm64/kvm/Makefile
>> +++ b/arch/arm64/kvm/Makefile
>> @@ -11,7 +11,7 @@ ARM=../../../arch/arm/kvm
>>
>> obj-$(CONFIG_KVM_ARM_HOST) += kvm.o
>>
>> -kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o
>> +kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/eventfd.o
>> kvm-$(CONFIG_KVM_ARM_HOST) += $(ARM)/arm.o $(ARM)/mmu.o $(ARM)/mmio.o
>> kvm-$(CONFIG_KVM_ARM_HOST) += $(ARM)/psci.o $(ARM)/perf.o
>>
>> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
>> index 18060ea..2c269dd 100644
>> --- a/virt/kvm/arm/vgic.c
>> +++ b/virt/kvm/arm/vgic.c
>> @@ -1449,6 +1449,7 @@ static bool vgic_process_maintenance(struct kvm_vcpu *vcpu)
>> u32 status = vgic_get_interrupt_status(vcpu);
>> struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
>> bool level_pending = false;
>> + struct kvm *kvm = vcpu->kvm;
>>
>> kvm_debug("STATUS = %08x\n", status);
>>
>> @@ -1484,6 +1485,17 @@ static bool vgic_process_maintenance(struct kvm_vcpu *vcpu)
>> */
>> vgic_dist_irq_clear_soft_pend(vcpu, vlr.irq);
>>
>> + /*
>> + * kvm_notify_acked_irq calls kvm_set_irq()
>> + * to reset the IRQ level. Need to release the
>> + * lock for kvm_set_irq to grab it.
>> + */
>> + spin_unlock(&dist->lock);
>> +
>> + kvm_notify_acked_irq(kvm, 0,
>> + vlr.irq - VGIC_NR_PRIVATE_IRQS);
>> + spin_lock(&dist->lock);
>> +
>> /* Any additional pending interrupt? */
>> if (vgic_dist_irq_get_level(vcpu, vlr.irq)) {
>> vgic_cpu_irq_set(vcpu, vlr.irq);
>> @@ -2490,3 +2502,36 @@ out_free_irq:
>> free_percpu_irq(vgic->maint_irq, kvm_get_running_vcpus());
>> return ret;
>> }
>> +
>> +int kvm_irq_map_gsi(struct kvm *kvm,
>> + struct kvm_kernel_irq_routing_entry *entries,
>> + int gsi)
>> +{
>> + return gsi;
>> +}
>> +
>> +int kvm_irq_map_chip_pin(struct kvm *kvm, unsigned irqchip, unsigned pin)
>> +{
>> + return pin;
>> +}
>> +
>> +int kvm_set_irq(struct kvm *kvm, int irq_source_id,
>> + u32 irq, int level, bool line_status)
>> +{
>> + unsigned int spi = irq + VGIC_NR_PRIVATE_IRQS;
>> +
>> + kvm_debug("irqfd sets vIRQ %d to %d\n", irq, level);
>
> I think it would be good to add a BUG_ON(!vgic_initialized(kvm)) here
> and convert the kvm_debug into a tracepoint.
>
>> +
>> + if (spi > kvm->arch.vgic.nr_irqs)
>> + return -EINVAL;
>> + return kvm_vgic_inject_irq(kvm, 0, spi, level);
>> +
>> +}
>> +
>> +/* MSI not implemented yet */
>> +int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
>> + struct kvm *kvm, int irq_source_id,
>> + int level, bool line_status)
>> +{
>> + return 0;
>> +}
>> --
>> 1.9.1
>>
>
> Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
>
> I can adress the two issues above when applying this if you don't have
> to do a re-spin.

Hi Christoffer,

I noticed the trace event already exists in #include
<trace/events/kvm.h>. I will do the modifications and re-post it quickly

Thanks

Eric
>
> -Christoffer
>