Re: [Qemu-devel] [PATCH v6 5/8] hw/intc/arm_gicv3_its: Implement support for in-kernel ITS emulation

[Auger Eric]

Hi Peter,

On 22/09/2016 17:03, Peter Maydell wrote:
> On 9 September 2016 at 18:30, Eric Auger <address@hidden> wrote:
>> From: Pavel Fedin <address@hidden>
>>
>> The ITS control frame is in-kernel emulated while accesses to the
>> GITS_TRANSLATER are mediated through the KVM_SIGNAL_MSI ioctl (MSI
>> direct MSI injection advertised by the CAP_SIGNAL_MSI capability)
>>
>> the kvm_gsi_direct_mapping is explicitly set to false to emphasize the
>> difference with GICv2M. Direct mapping cannot work with ITS since
>> the content of the MSI data is not the target interrupt ID but an
>> eventd id.
>>
>> GSI routing is advertised (kvm_gsi_routing_allowed) as well as
>> msi/irqfd signaling (kvm_msi_via_irqfd_allowed).
>>
>> A machine init done notifier still is used to compute the MSI frame
>> (GITS_TRANSLATER) GPA, which is passed through KVM_SIGNAL_MSI ioctl.
>>
>> Signed-off-by: Pavel Fedin <address@hidden>
>> Signed-off-by: Eric Auger <address@hidden>
>>
>> ---
>> v5 -> v6:
>> - now the kernel ITS init sequence has changed let's use the
>>   kvm_arm_register_device to set the CTRL frame base address
>> - use extract64()
>> - add migration blocker
>> - remove kvm_gsi_routing_allowed setting which is set in GICv3
>>   KVM device realize
>> - add migration_blocker
>>
>> v3 -> v4:
>> - include "qemu/osdep.h" and  "qapi/error.h"
>> - rename KVM_VGIC_V3_ADDR_TYPE_ITS into KVM_VGIC_ITS_ADDR_TYPE
>> - reword commit message
>> - change kvm_msi_via_irqfd_allowed definition (attached to irqfd dynamic
>>   availability + MSI controller availability)
>> - create the ITS KVM device (previously abstracted by the GICv3 KVM device)
>> - init sequence changed
>> - absolute GITS_TRANSLATER GPA stored
>>
>> Signed-off-by: Eric Auger <address@hidden>
>> ---
>>  hw/intc/Makefile.objs       |   1 +
>>  hw/intc/arm_gicv3_its_kvm.c | 136 
>> ++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 137 insertions(+)
>>  create mode 100644 hw/intc/arm_gicv3_its_kvm.c
>>
>> diff --git a/hw/intc/Makefile.objs b/hw/intc/Makefile.objs
>> index 23a39f7..9cca280 100644
>> --- a/hw/intc/Makefile.objs
>> +++ b/hw/intc/Makefile.objs
>> @@ -22,6 +22,7 @@ common-obj-$(CONFIG_OPENPIC) += openpic.o
>>  obj-$(CONFIG_APIC) += apic.o apic_common.o
>>  obj-$(CONFIG_ARM_GIC_KVM) += arm_gic_kvm.o
>>  obj-$(call land,$(CONFIG_ARM_GIC_KVM),$(TARGET_AARCH64)) += arm_gicv3_kvm.o
>> +obj-$(call land,$(CONFIG_ARM_GIC_KVM),$(TARGET_AARCH64)) += 
>> arm_gicv3_its_kvm.o
>>  obj-$(CONFIG_STELLARIS) += armv7m_nvic.o
>>  obj-$(CONFIG_EXYNOS4) += exynos4210_gic.o exynos4210_combiner.o
>>  obj-$(CONFIG_GRLIB) += grlib_irqmp.o
>> diff --git a/hw/intc/arm_gicv3_its_kvm.c b/hw/intc/arm_gicv3_its_kvm.c
>> new file mode 100644
>> index 0000000..b9d10dc
>> --- /dev/null
>> +++ b/hw/intc/arm_gicv3_its_kvm.c
>> @@ -0,0 +1,136 @@
>> +/*
>> + * KVM-based ITS implementation for a GICv3-based system
>> + *
>> + * Copyright (c) 2015 Samsung Electronics Co., Ltd.
>> + * Written by Pavel Fedin <address@hidden>
>> + *
>> + * This library is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU Lesser General Public
>> + * License as published by the Free Software Foundation; either
>> + * version 2 of the License, or (at your option) any later version.
>> + *
>> + * This library is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * Lesser General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU Lesser General Public
>> + * License along with this library; if not, see 
>> <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include "qemu/osdep.h"
>> +#include "qapi/error.h"
>> +#include "hw/intc/arm_gicv3_its_common.h"
>> +#include "sysemu/sysemu.h"
>> +#include "sysemu/kvm.h"
>> +#include "kvm_arm.h"
>> +#include "migration/migration.h"
>> +
>> +#define TYPE_KVM_ARM_ITS "arm-its-kvm"
>> +#define KVM_ARM_ITS(obj) OBJECT_CHECK(GICv3ITSState, (obj), 
>> TYPE_KVM_ARM_ITS)
>> +
>> +static int kvm_its_send_msi(GICv3ITSState *s, uint32_t value, uint16_t 
>> devid)
>> +{
>> +    struct kvm_msi msi;
>> +
>> +    msi.address_lo = extract64(s->gits_translater_gpa, 0, 32);
>> +    msi.address_hi = extract64(s->gits_translater_gpa, 32, 32);
>> +    msi.data = le32_to_cpu(value);
>> +    msi.flags = KVM_MSI_VALID_DEVID;
>> +    msi.devid = devid;
>> +    memset(msi.pad, 0, sizeof(msi.pad));
>> +
>> +    return kvm_vm_ioctl(kvm_state, KVM_SIGNAL_MSI, &msi);
>> +}
>> +
>> +typedef struct ItsInitNotifierParams {
>> +    Notifier notifier;
>> +    GICv3ITSState *s;
>> +} ItsInitNotifierParams;
>> +
>> +/* this notifier computes and stores the ITS MSI frame GPA */
>> +static void its_notify(Notifier *notifier, void *data)
>> +{
>> +    ItsInitNotifierParams *p = DO_UPCAST(ItsInitNotifierParams,
>> +                                         notifier, notifier);
>> +    GICv3ITSState *s = p->s;
>> +    MemoryRegion *mr = &s->iomem_its_translation;
>> +    MemoryRegionSection mrs;
>> +    uint64_t addr;
>> +
>> +    mrs = memory_region_find(mr, 0, 1);
>> +    addr = mrs.offset_within_address_space;
>> +    s->gits_translater_gpa = addr + 0x40;
> 
> This leaks a memory region reference.
Sure I did not notice memory_region_find is adding a reference.
> 
> Also, I think it would be simpler to just have kvm_its_send_msi() do
> 
>    if (unlikely(!s->translater_gpa_known)) {
>        s->gits_translater_gpa = ...;
>        s->translater_gpa_known = true;
>    }
My issue precisely is to get the absolue GPA of the ITS translater.
kvm_its_send_msi is called by the region write callback which works on
relative address wrt start of the translation region while kvm ioctl
uses the absolute GPA. I did not see any other way to retrieve the
absolute GPA than using a machine init done notifier.
> 
> rather than messing around with a machine-init-done notifier.
> 
>> +}
>> +
>> +static void kvm_arm_its_realize(DeviceState *dev, Error **errp)
>> +{
>> +    GICv3ITSState *s = ARM_GICV3_ITS_COMMON(dev);
>> +    ItsInitNotifierParams *p = g_new(ItsInitNotifierParams, 1);
>> +
>> +    s->dev_fd = kvm_create_device(kvm_state, KVM_DEV_TYPE_ARM_VGIC_ITS, 
>> false);
>> +    if (s->dev_fd < 0) {
>> +        error_setg_errno(errp, -s->dev_fd, "error creating in-kernel ITS");
>> +        return;
>> +    }
>> +
>> +    /* explicit init if the ITS */
> 
> "of the"
OK
> 
>> +    kvm_device_access(s->dev_fd, KVM_DEV_ARM_VGIC_GRP_CTRL,
>> +                      KVM_DEV_ARM_VGIC_CTRL_INIT, NULL, true);
>> +
>> +    /* register the base address */
>> +    kvm_arm_register_device(&s->iomem_its_cntrl, -1, 
>> KVM_DEV_ARM_VGIC_GRP_ADDR,
>> +                            KVM_VGIC_ITS_ADDR_TYPE, s->dev_fd);
>> +
>> +    gicv3_its_init_mmio(s, NULL);
>> +
>> +    p->notifier.notify = its_notify;
>> +    p->s = s;
>> +    qemu_add_machine_init_done_notifier(&p->notifier);
>> +
>> +    /*
>> +     * Block migration of a KVM GICv3 ITS device: the API for saving and
>> +     * restoring the state in the kernel is not yet available
>> +     */
>> +    error_setg(&s->migration_blocker, "vITS migration is not implemented");
>> +    migrate_add_blocker(s->migration_blocker);
>> +
>> +    kvm_msi_use_devid = true;
>> +    kvm_gsi_direct_mapping = false;
>> +    kvm_msi_via_irqfd_allowed = kvm_irqfds_enabled();
>> +}
>> +
>> +static void kvm_arm_its_init(Object *obj)
>> +{
>> +    GICv3ITSState *s = KVM_ARM_ITS(obj);
>> +
>> +    object_property_add_link(obj, "parent-gicv3",
>> +                             "kvm-arm-gicv3", (Object **)&s->gicv3,
>> +                             object_property_allow_set_link,
>> +                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
>> +                             &error_abort);
>> +}
>> +
>> +static void kvm_arm_its_class_init(ObjectClass *klass, void *data)
>> +{
>> +    DeviceClass *dc = DEVICE_CLASS(klass);
>> +    GICv3ITSCommonClass *icc = ARM_GICV3_ITS_COMMON_CLASS(klass);
>> +
>> +    dc->realize = kvm_arm_its_realize;
>> +    icc->send_msi = kvm_its_send_msi;
>> +}
>> +
>> +static const TypeInfo kvm_arm_its_info = {
>> +    .name = TYPE_KVM_ARM_ITS,
>> +    .parent = TYPE_ARM_GICV3_ITS_COMMON,
>> +    .instance_size = sizeof(GICv3ITSState),
>> +    .instance_init = kvm_arm_its_init,
>> +    .class_init = kvm_arm_its_class_init,
>> +};
>> +
>> +static void kvm_arm_its_register_types(void)
>> +{
>> +    type_register_static(&kvm_arm_its_info);
>> +}
>> +
>> +type_init(kvm_arm_its_register_types)
>> --
>> 2.5.5

Thank you for your time

Best Regards

Eric
> 
> thanks
> -- PMM
>