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

[Eric Auger <eric.auger@linaro.org>]

On 03/05/2015 03:20 PM, Marc Zyngier wrote:
> On 05/03/15 14:04, Eric Auger wrote:
>> Hi Marc,
>> On 03/05/2015 11:53 AM, Marc Zyngier wrote:
>>> 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@linaro.org>
>>>> Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
>>>>
>>>> ---
>>>> 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.
>> right. Also I think the vgic_present can be removed since
>> CONFIG_HAVE_KVM_IRQFD always is set when CONFIG_KVM_ARM_VGIC is set.
>> So overall this indeed can simply be replaced by Paolo's patch.
>>>
>>>>      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?
>>
>> I did that way since CONFIG_KVM_ARM_VGIC is not selected in the config
>> KVM section on 32b. Currently the IRQFD select location is same for arm
>> and arm64.
>>
>> do you prefer I select HAVE_KVM_IRQFD in the config KVM section, ie. at
>> the same place we select CONFIG_KVM_ARM_VGIC?
> 
> We cannot have irqfd without vgic, can we? Or am I misunderstanding the
> dependency chain entirely?

No we can't have irqfd without vgic.
> 
> [...]
> 
>> Do I need to post a v10 based on Paolo's patch?
> 
> I don't think so, we can probably fixup things when we merge things.
> Let's sort the above first, and we should be good.

OK

Thanks
Eric
> 
> Thanks,
> 
> 	M.
>