Re: [PATCH v9 5/5] KVM: arm/arm64: add irqfd support

From: Marc Zyngier
Date: Thu Mar 05 2015 - 05:53:28 EST

On 04/03/15 10:14, 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@xxxxxxxxxx>
> Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
>
> ---
> v8 -> v9:
> - replace kvm_debug by trace_kvm_set_irq and add
> BUG_ON(!vgic_initialized(kvm));
>
> 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
>
> Conflicts:
> arch/arm64/kvm/Kconfig
> ---
> 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 | 48 +++++++++++++++++++++++++++++++++++++++
> 9 files changed, 70 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index b112efc..b265d8e 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2234,7 +2234,7 @@ 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
> @@ -2260,6 +2260,10 @@ 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 aae5242..d735a3e 100644
> --- a/arch/arm/kvm/Kconfig
> +++ b/arch/arm/kvm/Kconfig
> @@ -27,6 +27,7 @@ config KVM
> select KVM_GENERIC_DIRTYLOG_READ_PROTECT
> select SRCU
> 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.
> @@ -58,6 +59,7 @@ 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 443b8be..539c1a5 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 5300d5a..4313776 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -175,6 +175,11 @@ 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

Nitpick: we have "select HAVE_KVM_IRQFD", so we can lose the #ifdef-ery.

> 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 3ef77a4..c154c0b 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -191,6 +191,9 @@ 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 039d8cf..143c9fd 100644
> --- a/arch/arm64/kvm/Kconfig
> +++ b/arch/arm64/kvm/Kconfig
> @@ -29,6 +29,7 @@ config KVM
> select KVM_ARM_TIMER
> select KVM_GENERIC_DIRTYLOG_READ_PROTECT
> select SRCU
> + select HAVE_KVM_EVENTFD
> ---help---
> Support hosting virtualized guest machines.
>
> @@ -53,6 +54,7 @@ config KVM_ARM_MAX_VCPUS
> config KVM_ARM_VGIC
> bool
> depends on KVM_ARM_HOST && OF
> + select HAVE_KVM_IRQFD

Hmmm. There is way too many selects here. Can't we just select it with
CONFIG_KVM_ARM_VGIC, and be done with it?

> ---help---
> Adds support for a hardware assisted, in-kernel GIC emulation.
>
> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> index 4e6e09e..0dffb5f 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 4e9b6d3..2dfb299 100644
> --- a/virt/kvm/arm/vgic.c
> +++ b/virt/kvm/arm/vgic.c
> @@ -31,6 +31,7 @@
> #include <asm/kvm_emulate.h>
> #include <asm/kvm_arm.h>
> #include <asm/kvm_mmu.h>
> +#include <trace/events/kvm.h>
>
> /*
> * How the whole thing works (courtesy of Christoffer Dall):
> @@ -1083,6 +1084,7 @@ 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);
>
> @@ -1118,6 +1120,17 @@ 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);
> +

I tried hard to break that one, and failed. It must be correct! ;-)

> /* Any additional pending interrupt? */
> if (vgic_dist_irq_get_level(vcpu, vlr.irq)) {
> vgic_cpu_irq_set(vcpu, vlr.irq);
> @@ -1911,3 +1924,38 @@ 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;
> +
> + trace_kvm_set_irq(irq, level, irq_source_id);
> +
> + BUG_ON(!vgic_initialized(kvm));
> +
> + 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;
> +}
>

Despite from the nits mentionned before, this looks good, and I think we
should merge it in 4.1 (or whatever this is called).

So for the whole series:

Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>

M.
--
Jazz is not dead. It just smells funny...
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