Re: [PATCH v2 12/18] KVM: arm64: add a new vcpu device control group for SPEv1

Andrew Murray
2019-12-24T12:30:21Z

On Sun, Dec 22, 2019 at 11:03:04AM +0000, Marc Zyngier wrote:
> On Fri, 20 Dec 2019 14:30:19 +0000,
> Andrew Murray <andrew.murray@arm.com> wrote:
> >
> > From: Sudeep Holla <sudeep.holla@arm.com>
> >
> > To configure the virtual SPEv1 overflow interrupt number, we use the
> > vcpu kvm_device ioctl, encapsulating the KVM_ARM_VCPU_SPE_V1_IRQ
> > attribute within the KVM_ARM_VCPU_SPE_V1_CTRL group.
> >
> > After configuring the SPEv1, call the vcpu ioctl with attribute
> > KVM_ARM_VCPU_SPE_V1_INIT to initialize the SPEv1.
> >
> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> > Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> > ---
> > Documentation/virt/kvm/devices/vcpu.txt | 28 ++++
> > arch/arm64/include/asm/kvm_host.h | 2 +-
> > arch/arm64/include/uapi/asm/kvm.h | 4 +
> > arch/arm64/kvm/Makefile | 1 +
> > arch/arm64/kvm/guest.c | 6 +
> > arch/arm64/kvm/reset.c | 3 +
> > include/kvm/arm_spe.h | 45 +++++++
> > include/uapi/linux/kvm.h | 1 +
> > virt/kvm/arm/arm.c | 1 +
> > virt/kvm/arm/spe.c | 163 ++++++++++++++++++++++++
> > 10 files changed, 253 insertions(+), 1 deletion(-)
> > create mode 100644 virt/kvm/arm/spe.c
> >
> > diff --git a/Documentation/virt/kvm/devices/vcpu.txt b/Documentation/virt/kvm/devices/vcpu.txt
> > index 6f3bd64a05b0..cefad056d677 100644
> > --- a/Documentation/virt/kvm/devices/vcpu.txt
> > +++ b/Documentation/virt/kvm/devices/vcpu.txt
> > @@ -74,3 +74,31 @@ Specifies the base address of the stolen time structure for this VCPU. The
> > base address must be 64 byte aligned and exist within a valid guest memory
> > region. See Documentation/virt/kvm/arm/pvtime.txt for more information
> > including the layout of the stolen time structure.
> > +
> > +4. GROUP: KVM_ARM_VCPU_SPE_V1_CTRL
> > +Architectures: ARM64
> > +
> > +4.1. ATTRIBUTE: KVM_ARM_VCPU_SPE_V1_IRQ
> > +Parameters: in kvm_device_attr.addr the address for SPE buffer overflow interrupt
> > + is a pointer to an int
> > +Returns: -EBUSY: The SPE overflow interrupt is already set
> > + -ENXIO: The overflow interrupt not set when attempting to get it
> > + -ENODEV: SPEv1 not supported
> > + -EINVAL: Invalid SPE overflow interrupt number supplied or
> > + trying to set the IRQ number without using an in-kernel
> > + irqchip.
> > +
> > +A value describing the SPEv1 (Statistical Profiling Extension v1) overflow
> > +interrupt number for this vcpu. This interrupt should be PPI and the interrupt
> > +type and number must be same for each vcpu.
> > +
> > +4.2 ATTRIBUTE: KVM_ARM_VCPU_SPE_V1_INIT
> > +Parameters: no additional parameter in kvm_device_attr.addr
> > +Returns: -ENODEV: SPEv1 not supported or GIC not initialized
> > + -ENXIO: SPEv1 not properly configured or in-kernel irqchip not
> > + configured as required prior to calling this attribute
> > + -EBUSY: SPEv1 already initialized
> > +
> > +Request the initialization of the SPEv1. If using the SPEv1 with an in-kernel
> > +virtual GIC implementation, this must be done after initializing the in-kernel
> > +irqchip.
> > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> > index 333c6491bec7..d00f450dc4cd 100644
> > --- a/arch/arm64/include/asm/kvm_host.h
> > +++ b/arch/arm64/include/asm/kvm_host.h
> > @@ -39,7 +39,7 @@
> >
> > #define KVM_MAX_VCPUS VGIC_V3_MAX_CPUS
> >
> > -#define KVM_VCPU_MAX_FEATURES 7
> > +#define KVM_VCPU_MAX_FEATURES 8
> >
> > #define KVM_REQ_SLEEP \
> > KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
> > diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> > index 820e5751ada7..905a73f30079 100644
> > --- a/arch/arm64/include/uapi/asm/kvm.h
> > +++ b/arch/arm64/include/uapi/asm/kvm.h
> > @@ -106,6 +106,7 @@ struct kvm_regs {
> > #define KVM_ARM_VCPU_SVE 4 /* enable SVE for this CPU */
> > #define KVM_ARM_VCPU_PTRAUTH_ADDRESS 5 /* VCPU uses address authentication */
> > #define KVM_ARM_VCPU_PTRAUTH_GENERIC 6 /* VCPU uses generic authentication */
> > +#define KVM_ARM_VCPU_SPE_V1 7 /* Support guest SPEv1 */
> >
> > struct kvm_vcpu_init {
> > __u32 target;
> > @@ -326,6 +327,9 @@ struct kvm_vcpu_events {
> > #define KVM_ARM_VCPU_TIMER_IRQ_PTIMER 1
> > #define KVM_ARM_VCPU_PVTIME_CTRL 2
> > #define KVM_ARM_VCPU_PVTIME_IPA 0
> > +#define KVM_ARM_VCPU_SPE_V1_CTRL 3
> > +#define KVM_ARM_VCPU_SPE_V1_IRQ 0
> > +#define KVM_ARM_VCPU_SPE_V1_INIT 1
> >
> > /* KVM_IRQ_LINE irq field index values */
> > #define KVM_ARM_IRQ_VCPU2_SHIFT 28
> > diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> > index 5ffbdc39e780..526f3bf09321 100644
> > --- a/arch/arm64/kvm/Makefile
> > +++ b/arch/arm64/kvm/Makefile
> > @@ -37,3 +37,4 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-debug.o
> > kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/irqchip.o
> > kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arch_timer.o
> > kvm-$(CONFIG_KVM_ARM_PMU) += $(KVM)/arm/pmu.o
> > +kvm-$(CONFIG_KVM_ARM_SPE) += $(KVM)/arm/spe.o
> > diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> > index 2fff06114a8f..50fea538b8bd 100644
> > --- a/arch/arm64/kvm/guest.c
> > +++ b/arch/arm64/kvm/guest.c
> > @@ -874,6 +874,8 @@ int kvm_arm_vcpu_arch_set_attr(struct kvm_vcpu *vcpu,
> > break;
> > case KVM_ARM_VCPU_PVTIME_CTRL:
> > ret = kvm_arm_pvtime_set_attr(vcpu, attr);
> > + case KVM_ARM_VCPU_SPE_V1_CTRL:
> > + ret = kvm_arm_spe_v1_set_attr(vcpu, attr);
> > break;
> > default:
> > ret = -ENXIO;
> > @@ -897,6 +899,8 @@ int kvm_arm_vcpu_arch_get_attr(struct kvm_vcpu *vcpu,
> > break;
> > case KVM_ARM_VCPU_PVTIME_CTRL:
> > ret = kvm_arm_pvtime_get_attr(vcpu, attr);
> > + case KVM_ARM_VCPU_SPE_V1_CTRL:
> > + ret = kvm_arm_spe_v1_get_attr(vcpu, attr);
> > break;
> > default:
> > ret = -ENXIO;
> > @@ -920,6 +924,8 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
> > break;
> > case KVM_ARM_VCPU_PVTIME_CTRL:
> > ret = kvm_arm_pvtime_has_attr(vcpu, attr);
> > + case KVM_ARM_VCPU_SPE_V1_CTRL:
> > + ret = kvm_arm_spe_v1_has_attr(vcpu, attr);
> > break;
> > default:
> > ret = -ENXIO;
> > diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> > index f4a8ae918827..cf17aff1489d 100644
> > --- a/arch/arm64/kvm/reset.c
> > +++ b/arch/arm64/kvm/reset.c
> > @@ -80,6 +80,9 @@ int kvm_arch_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> > case KVM_CAP_ARM_INJECT_SERROR_ESR:
> > r = cpus_have_const_cap(ARM64_HAS_RAS_EXTN);
> > break;
> > + case KVM_CAP_ARM_SPE_V1:
> > + r = kvm_arm_support_spe_v1();
> > + break;
> > case KVM_CAP_SET_GUEST_DEBUG:
> > case KVM_CAP_VCPU_ATTRIBUTES:
> > r = 1;
> > diff --git a/include/kvm/arm_spe.h b/include/kvm/arm_spe.h
> > index 30c40b1bc385..d1f3c564dfd0 100644
> > --- a/include/kvm/arm_spe.h
> > +++ b/include/kvm/arm_spe.h
> > @@ -8,6 +8,7 @@
> >
> > #include <uapi/linux/kvm.h>
> > #include <linux/kvm_host.h>
> > +#include <linux/cpufeature.h>
> >
> > struct kvm_spe {
> > int irq_num;
> > @@ -18,8 +19,52 @@ struct kvm_spe {
> >
> > #ifdef CONFIG_KVM_ARM_SPE
> > #define kvm_arm_spe_v1_ready(v) ((v)->arch.spe.ready)
> > +#define kvm_arm_spe_irq_initialized(v) \
> > + ((v)->arch.spe.irq_num >= VGIC_NR_SGIS && \
> > + (v)->arch.spe.irq_num <= VGIC_MAX_PRIVATE)
>
> This is buggy, as it accepts 32 as a valid interrupt (which obviously
> isn't a PPI). Having fixed it, this is a duplicate of irq_is_ppi().

I'll replace that line with irq_is_ppi.

>
> And that's where we can finally confirm that 'irq_num' is a GIC
> INTID. Please name it as such.

OK.

>
> > +
> > +static inline bool kvm_arm_support_spe_v1(void)
> > +{
> > + u64 dfr0 = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
> > +
> > + return !!cpuid_feature_extract_unsigned_field(dfr0,
> > + ID_AA64DFR0_PMSVER_SHIFT);
> > +}
> > +
> > +int kvm_arm_spe_v1_set_attr(struct kvm_vcpu *vcpu,
> > + struct kvm_device_attr *attr);
> > +int kvm_arm_spe_v1_get_attr(struct kvm_vcpu *vcpu,
> > + struct kvm_device_attr *attr);
> > +int kvm_arm_spe_v1_has_attr(struct kvm_vcpu *vcpu,
> > + struct kvm_device_attr *attr);
> > +int kvm_arm_spe_v1_enable(struct kvm_vcpu *vcpu);
> > #else
> > #define kvm_arm_spe_v1_ready(v) (false)
> > +#define kvm_arm_support_spe_v1() (false)
> > +#define kvm_arm_spe_irq_initialized(v) (false)
> > +
> > +static inline int kvm_arm_spe_v1_set_attr(struct kvm_vcpu *vcpu,
> > + struct kvm_device_attr *attr)
> > +{
> > + return -ENXIO;
> > +}
> > +
> > +static inline int kvm_arm_spe_v1_get_attr(struct kvm_vcpu *vcpu,
> > + struct kvm_device_attr *attr)
> > +{
> > + return -ENXIO;
> > +}
> > +
> > +static inline int kvm_arm_spe_v1_has_attr(struct kvm_vcpu *vcpu,
> > + struct kvm_device_attr *attr)
> > +{
> > + return -ENXIO;
> > +}
> > +
> > +static inline int kvm_arm_spe_v1_enable(struct kvm_vcpu *vcpu)
> > +{
> > + return 0;
> > +}
> > #endif /* CONFIG_KVM_ARM_SPE */
> >
> > #endif /* __ASM_ARM_KVM_SPE_H */
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index f0a16b4adbbd..1a362c230e4a 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -1009,6 +1009,7 @@ struct kvm_ppc_resize_hpt {
> > #define KVM_CAP_PPC_GUEST_DEBUG_SSTEP 176
> > #define KVM_CAP_ARM_NISV_TO_USER 177
> > #define KVM_CAP_ARM_INJECT_EXT_DABT 178
> > +#define KVM_CAP_ARM_SPE_V1 179
> >
> > #ifdef KVM_CAP_IRQ_ROUTING
> >
> > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> > index 12e0280291ce..340d2388ee2c 100644
> > --- a/virt/kvm/arm/arm.c
> > +++ b/virt/kvm/arm/arm.c
> > @@ -22,6 +22,7 @@
> > #include <trace/events/kvm.h>
> > #include <kvm/arm_pmu.h>
> > #include <kvm/arm_psci.h>
> > +#include <kvm/arm_spe.h>
> >
> > #define CREATE_TRACE_POINTS
> > #include "trace.h"
> > diff --git a/virt/kvm/arm/spe.c b/virt/kvm/arm/spe.c
> > new file mode 100644
> > index 000000000000..83ac2cce2cc3
> > --- /dev/null
> > +++ b/virt/kvm/arm/spe.c
> > @@ -0,0 +1,163 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (C) 2019 ARM Ltd.
> > + */
> > +
> > +#include <linux/cpu.h>
> > +#include <linux/kvm.h>
> > +#include <linux/kvm_host.h>
> > +#include <linux/uaccess.h>
> > +#include <asm/kvm_emulate.h>
> > +#include <kvm/arm_spe.h>
> > +#include <kvm/arm_vgic.h>
> > +
> > +int kvm_arm_spe_v1_enable(struct kvm_vcpu *vcpu)
> > +{
> > + if (!vcpu->arch.spe.created)
> > + return 0;
>
> Shouldn't it be an error to enable something that doesn't exist?

It looks like this has adopted the same approach as kvm_arm_pmu_v3_enable. In
kvm_vcpu_first_run_init we attempt to enable pmu v3 and spe - without first
checking they exist.

>
> > +
> > + /*
> > + * A valid interrupt configuration for the SPE is either to have a
>
> either?
>
> > + * properly configured interrupt number and using an in-kernel irqchip.
> > + */
> > + if (irqchip_in_kernel(vcpu->kvm)) {
> > + int irq = vcpu->arch.spe.irq_num;
> > +
> > + if (!kvm_arm_spe_irq_initialized(vcpu))
> > + return -EINVAL;
> > +
> > + if (!irq_is_ppi(irq))
> > + return -EINVAL;
> > + }
> > +
> > + vcpu->arch.spe.ready = true;
>
> And SPE is then ready even when we don't have an in-kernel irqchip?

I recall in Sudeep's previous patchset that you suggested we don't support
SPE without an in-kernel irqchip. I'll update to reflect that feedback.

>
> > +
> > + return 0;
> > +}
> > +
> > +static int kvm_arm_spe_v1_init(struct kvm_vcpu *vcpu)
> > +{
> > + if (!kvm_arm_support_spe_v1())
> > + return -ENODEV;
> > +
> > + if (!test_bit(KVM_ARM_VCPU_SPE_V1, vcpu->arch.features))
> > + return -ENXIO;
> > +
> > + if (vcpu->arch.spe.created)
> > + return -EBUSY;
> > +
> > + if (irqchip_in_kernel(vcpu->kvm)) {
> > + int ret;
> > +
> > + /*
> > + * If using the SPE with an in-kernel virtual GIC
> > + * implementation, we require the GIC to be already
> > + * initialized when initializing the SPE.
> > + */
> > + if (!vgic_initialized(vcpu->kvm))
> > + return -ENODEV;
> > +
> > + ret = kvm_vgic_set_owner(vcpu, vcpu->arch.spe.irq_num,
> > + &vcpu->arch.spe);
> > + if (ret)
> > + return ret;
> > + }
> > +
> > + vcpu->arch.spe.created = true;
>
> Same problem.
>
> > + return 0;
> > +}
> > +
> > +/*
> > + * For one VM the interrupt type must be same for each vcpu.
> > + * As a PPI, the interrupt number is the same for all vcpus,
> > + * while as an SPI it must be a separate number per vcpu.
>
> Why do you want to support SPIs at all? And it isn't what
> kvm_arm_spe_irq_initialized claims to be doing.

I don't think we do. I think it's expected that the SPE interrupt is a PPI,
at least that's what the SPE driver expects. I'll simplify this.

>
> > + */
> > +static bool spe_irq_is_valid(struct kvm *kvm, int irq)
> > +{
> > + int i;
> > + struct kvm_vcpu *vcpu;
> > +
> > + kvm_for_each_vcpu(i, vcpu, kvm) {
> > + if (!kvm_arm_spe_irq_initialized(vcpu))
> > + continue;
> > +
> > + if (vcpu->arch.spe.irq_num != irq)
> > + return false;
> > + }
> > +
> > + return true;
> > +}
> > +
> > +int kvm_arm_spe_v1_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
> > +{
> > + switch (attr->attr) {
> > + case KVM_ARM_VCPU_SPE_V1_IRQ: {
> > + int __user *uaddr = (int __user *)(long)attr->addr;
> > + int irq;
> > +
> > + if (!irqchip_in_kernel(vcpu->kvm))
> > + return -EINVAL;
>
> Here, you forbid setting the IRQ for a VM that doesn't have an
> in-kernel irqchip. And yet below, you're happy to initialise it.
>
> > +
> > + if (!test_bit(KVM_ARM_VCPU_SPE_V1, vcpu->arch.features))
> > + return -ENODEV;
> > +
> > + if (get_user(irq, uaddr))
> > + return -EFAULT;
> > +
> > + /* The SPE overflow interrupt can be a PPI only */
> > + if (!(irq_is_ppi(irq)))
> > + return -EINVAL;
>
> Ah, so you do know about irq_is_ppi()...
>
> > +
> > + if (!spe_irq_is_valid(vcpu->kvm, irq))
>
> But why don't you fold the interrupt validity checks in this helper?

That makes sense.

>
> > + return -EINVAL;
> > +
> > + if (kvm_arm_spe_irq_initialized(vcpu))
> > + return -EBUSY;
> > +
> > + kvm_debug("Set kvm ARM SPE irq: %d\n", irq);
> > + vcpu->arch.spe.irq_num = irq;
> > + return 0;
> > + }
> > + case KVM_ARM_VCPU_SPE_V1_INIT:
> > + return kvm_arm_spe_v1_init(vcpu);
> > + }
> > +
> > + return -ENXIO;
> > +}
> > +
> > +int kvm_arm_spe_v1_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
> > +{
> > + switch (attr->attr) {
> > + case KVM_ARM_VCPU_SPE_V1_IRQ: {
> > + int __user *uaddr = (int __user *)(long)attr->addr;
> > + int irq;
> > +
> > + if (!irqchip_in_kernel(vcpu->kvm))
> > + return -EINVAL;
> > +
> > + if (!test_bit(KVM_ARM_VCPU_SPE_V1, vcpu->arch.features))
> > + return -ENODEV;
> > +
> > + if (!kvm_arm_spe_irq_initialized(vcpu))
> > + return -ENXIO;
> > +
> > + irq = vcpu->arch.spe.irq_num;
> > + return put_user(irq, uaddr);
> > + }
> > + }
> > +
> > + return -ENXIO;
> > +}
> > +
> > +int kvm_arm_spe_v1_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
> > +{
> > + switch (attr->attr) {
> > + case KVM_ARM_VCPU_SPE_V1_IRQ:
> > + case KVM_ARM_VCPU_SPE_V1_INIT:
> > + if (kvm_arm_support_spe_v1() &&
> > + test_bit(KVM_ARM_VCPU_SPE_V1, vcpu->arch.features))
> > + return 0;
>
> It is interesting that all the user interface is designed with the
> feature being optional in mind, and yet you've removed all the
> necessary handling code.

Yeah I broke that, I'll fix it.

Thanks,

Andrew Murray

>
> M.
>
> --
> Jazz is not dead, it just smells funny.