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

[Andrew Murray]

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@xxxxxxx> wrote:
> > 
> > From: Sudeep Holla <sudeep.holla@xxxxxxx>
> > 
> > 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@xxxxxxx>
> > Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx>
> > ---
> >  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.