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Message-ID: <541159D5.40804@linaro.org>
Date: Thu, 11 Sep 2014 10:14:13 +0200
From: Eric Auger <eric.auger@...aro.org>
To: Christoffer Dall <christoffer.dall@...aro.org>
CC: eric.auger@...com, marc.zyngier@....com,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
kvm@...r.kernel.org, alex.williamson@...hat.com,
joel.schopp@....com, kim.phillips@...escale.com, paulus@...ba.org,
gleb@...nel.org, pbonzini@...hat.com, linux-kernel@...r.kernel.org,
patches@...aro.org, will.deacon@....com,
a.motakis@...tualopensystems.com, a.rigo@...tualopensystems.com,
john.liuli@...wei.com
Subject: Re: [PATCH v3] ARM: KVM: add irqfd support
On 09/11/2014 05:09 AM, Christoffer Dall wrote:
> On Mon, Sep 01, 2014 at 10:53:04AM +0200, Eric Auger wrote:
>> This patch enables irqfd on ARM.
>>
>> irqfd framework enables to inject a virtual IRQ into a guest upon an
>> eventfd trigger. User-side uses KVM_IRQFD VM ioctl to provide KVM with
>> a kvm_irqfd struct that associates a VM, an eventfd, a virtual IRQ number
>> (aka. the gsi). When an actor signals the eventfd (typically a VFIO
>> platform driver), the kvm irqfd subsystem injects the provided virtual
>> IRQ into the guest.
>>
>> Resamplefd also is supported for level sensitive interrupts, ie. the
>> user can provide another eventfd that is triggered when the completion
>> of the virtual IRQ (gsi) is detected by the GIC.
>>
>> The gsi must correspond to a shared peripheral interrupt (SPI), ie the
>> GIC interrupt ID is gsi+32.
>>
>> this patch enables CONFIG_HAVE_KVM_EVENTFD and CONFIG_HAVE_KVM_IRQFD.
>> CONFIG_HAVE_KVM_IRQCHIP is removed. No IRQ routing table is used
>> (irqchip.c and irqcomm.c are not used).
>>
>> Both KVM_CAP_IRQFD & KVM_CAP_IRQFD_RESAMPLE capabilities are exposed
>>
>> Signed-off-by: Eric Auger <eric.auger@...aro.org>
>>
>> ---
>>
>> This patch serie deprecates the previous serie featuring GSI routing
>> (https://patches.linaro.org/32261/)
>>
>> The patch serie has the following dependencies:
>> - arm/arm64: KVM: Various VGIC cleanups and improvements
>> https://lists.cs.columbia.edu/pipermail/kvmarm/2014-June/009979.html
>> - "KVM: EVENTFD: remove inclusion of irq.h"
>>
>> All pieces can be found on git://git.linaro.org/people/eric.auger/linux.git
>> branch irqfd_norouting_integ_v3
>>
>> This work was tested with Calxeda Midway xgmac main interrupt with
>> qemu-system-arm and QEMU VFIO platform device.
>>
>> 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 | 5 +++-
>> arch/arm/include/uapi/asm/kvm.h | 3 +++
>> arch/arm/kvm/Kconfig | 4 +--
>> arch/arm/kvm/Makefile | 2 +-
>> arch/arm/kvm/arm.c | 3 +++
>> virt/kvm/arm/vgic.c | 56 ++++++++++++++++++++++++++++++++++++---
>> 6 files changed, 65 insertions(+), 8 deletions(-)
>>
>> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
>> index beae3fd..8118b12 100644
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -2204,7 +2204,7 @@ into the hash PTE second double word).
>> 4.75 KVM_IRQFD
>>
>> Capability: KVM_CAP_IRQFD
>> -Architectures: x86 s390
>> +Architectures: x86 s390 arm
>> Type: vm ioctl
>> Parameters: struct kvm_irqfd (in)
>> Returns: 0 on success, -1 on error
>> @@ -2230,6 +2230,9 @@ 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 injected must be a shared peripheral interrupt (SPI).
>> +This means the programmed GIC interrupt ID is gsi+32.
>> +
>
> See above comment.
Hi Christoffer,
sorry which comment do you refer to? wrt your last comment do you
consider PPI injection support is a mandated feature for this patch to
be upstreamable?
>
>> 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 e6ebdd3..3034c66 100644
>> --- a/arch/arm/include/uapi/asm/kvm.h
>> +++ b/arch/arm/include/uapi/asm/kvm.h
>> @@ -194,6 +194,9 @@ 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 466bd29..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.
>> @@ -55,7 +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_IRQCHIP
>> + select HAVE_KVM_IRQFD
>> default y
>> ---help---
>> Adds support for a hardware assisted, in-kernel GIC emulation.
>> @@ -63,7 +64,6 @@ config KVM_ARM_VGIC
>> config KVM_ARM_TIMER
>> bool "KVM support for Architected Timers"
>> depends on KVM_ARM_VGIC && ARM_ARCH_TIMER
>> - select HAVE_KVM_IRQCHIP
>> default y
>> ---help---
>> Adds support for the Architected Timers in virtual machines
>> 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 a99e0cd..6ba454a 100644
>> --- a/arch/arm/kvm/arm.c
>> +++ b/arch/arm/kvm/arm.c
>> @@ -181,6 +181,9 @@ 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:
>> +#endif
>> case KVM_CAP_DEVICE_CTRL:
>> case KVM_CAP_USER_MEMORY:
>> case KVM_CAP_SYNC_MMU:
>> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
>> index 7164d2e..586bd11 100644
>> --- a/virt/kvm/arm/vgic.c
>> +++ b/virt/kvm/arm/vgic.c
>> @@ -1334,7 +1334,10 @@ epilog:
>> 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;
>> + int is_assigned_irq;
>>
>> kvm_debug("STATUS = %08x\n", status);
>>
>> @@ -1351,6 +1354,7 @@ static bool vgic_process_maintenance(struct kvm_vcpu *vcpu)
>> struct vgic_lr vlr = vgic_get_lr(vcpu, lr);
>> BUG_ON(vgic_irq_is_edge(vcpu, vlr.irq));
>>
>> + spin_lock(&dist->lock);
>> vgic_irq_clear_queued(vcpu, vlr.irq);
>> WARN_ON(vlr.state & LR_STATE_MASK);
>> vlr.state = 0;
>> @@ -1363,6 +1367,18 @@ static bool vgic_process_maintenance(struct kvm_vcpu *vcpu)
>> * interrupt.
>> */
>> vgic_dist_irq_clear_soft_pend(vcpu, vlr.irq);
>> + spin_unlock(&dist->lock);
>
> may be worth a small comment saying that we unlock the distributor
> lock to allow kvm_notify_acked_irq() to come back to injecting an IRQ
> which grabs the dist->lock again.
yes sure.
>
>> +
>> + is_assigned_irq = kvm_irq_has_notifier(kvm, 0,
>> + vlr.irq - VGIC_NR_PRIVATE_IRQS);
>
> is is_assigned_irq really accurately describing the state you are
> determining here? Can't you have an irqfd without a resamplefd, or did
> I get this wrong? In any case, this code may be simpler if you simply
> inline the call to kvm_irq_has_notifier or name the variable
> 'irq_has_notifier'.
Yes you can have an irqfd without resamplefd, typically for edge
sensitive IRQs. But in that case you do not need to call the resamplefd
notifier (kvm_notify_acked_irq). I think this is what is achieved here.
But I agree is_assigned_irq name is misleading. I should rename it into
something like has_resampler.
>
>> +
>> + if (is_assigned_irq) {
>> + kvm_debug("EOI irqchip routed vIRQ %d\n",
>> + vlr.irq);
>
> EOI irqchip routed vIRQ X?
>
> -ECANTPARSE, how about "Guest EOIed vIRQ %d on CPU %d\n" ?
definitively makes sense all the more so now routing has been removed,
the message is outdated.
>
>> + 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)) {
>> @@ -1377,6 +1393,8 @@ static bool vgic_process_maintenance(struct kvm_vcpu *vcpu)
>> vgic_cpu_irq_clear(vcpu, vlr.irq);
>> }
>>
>> + spin_unlock(&dist->lock);
>> +
>> /*
>> * Despite being EOIed, the LR may not have
>> * been marked as empty.
>> @@ -1441,14 +1459,10 @@ void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu)
>>
>> void kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu)
>> {
>> - struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
>> -
>> if (!irqchip_in_kernel(vcpu->kvm))
>> return;
>>
>> - spin_lock(&dist->lock);
>> __kvm_vgic_sync_hwstate(vcpu);
>> - spin_unlock(&dist->lock);
>> }
>>
>> int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu)
>> @@ -2183,3 +2197,37 @@ struct kvm_device_ops kvm_arm_vgic_v2_ops = {
>> .get_attr = vgic_get_attr,
>> .has_attr = vgic_has_attr,
>> };
>> +
>> +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)
>
> what does line_status indicate?
well, I am embarrassed to answer. If I am not wrong all the caller set
the line_status to false (eventfd.c, assigned_dev.c). If seems however
this param was exploited along with GSI routing when the IRQ is
eventually routed to the IOAPIC (ioapic_set_irq). is that dead code?
>
>> +{
>> + int r = -EINVAL;
>> + unsigned int spi = irq + VGIC_NR_PRIVATE_IRQS;
>> +
>> + if (spi > KVM_ARM_IRQ_GIC_MAX)
>> + return r;
>
> can you just do 'return -EINVAL' here and not initialize r above.
sure
Many thanks
Best Regards
Eric
>
>> +
>> + kvm_debug("Inject irqchip routed vIRQ %d\n", irq);
>> + r = kvm_vgic_inject_irq(kvm, 0, spi, level);
>> + return r;
>> +}
>> +
>> +/* 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
>>
>
> Besides the cosmetics and the missing PPI support, this is looking good!
>
> Thanks,
> -Christoffer
>
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